2.1 General Instructions

EPA SWMM can also be run as a console application from the command line within a DOS window. In this case the study area data are placed into a text file and results are written to a text file. The command line for running SWMM in this fashion is: runswmm inpfile rptfile outfile where inpfile is the name of the input file, rptfile is the name of the output report file, and outfile is the name of an optional binary output file. The latter stores all time series results in a special binary format that will require a separate post-processor program for viewing. If no binary output file name is supplied then all time series results will appear in the report file. As written, the above command assumes that you are working in the directory in which EPA SWMM was installed or that this directory has been added to the PATH variable in your user profile. Otherwise full pathnames for the runswmm executable and the files on the command line must be used.

2.2 Input File Format

The input file for command line SWMM has the same format as the project file used by the Windows version of the program. Figure D-1 illustrates an example SWMM 5 input file. It is organized in sections, where each section begins with a keyword enclosed in brackets. The various section keywords are listed below.

[TITLE] project title [OPTIONS] analysis options [REPORT] output reporting instructions [FILES] interface file options

[RAINGAGES] rain gage information [EVAPORATION] evaporation data [TEMPERATURE] air temperature and snow melt data [ADJUSTMENTS] monthly adjustments applied to climate variables

[SUBCATCHMENTS] basic subcatchment information [SUBAREAS] subcatchment impervious/pervious subarea data [INFILTRATION] subcatchment infiltration parameters [LID_CONTROLS] low impact development control information [LID_USAGE] assignment of LID controls to subcatchments

[AQUIFERS] groundwater aquifer parameters [GROUNDWATER] subcatchment groundwater parameters [GWF] groundwater flow expressions [SNOWPACKS] subcatchment snow pack parameters

[JUNCTIONS] junction node information [OUTFALLS] outfall node information [DIVIDERS] flow divider node information [STORAGE] storage node information

[CONDUITS] conduit link information [PUMPS] pump link information [ORIFICES] orifice link information [WEIRS] weir link information [OUTLETS] outlet link information

[XSECTIONS] conduit, orifice, and weir cross-section geometry [TRANSECTS] transect geometry for conduits with irregular cross-sections [STREETS] cross-section geometry for street conduits [INLETS] design data for storm drain inlets [INLET_USAGE] assignment of inlets to street and channel conduits [LOSSES] conduit entrance/exit losses and flap valves [CONTROLS] rules that control pump and regulator operation

[POLLUTANTS] pollutant information [LANDUSES] land use categories [COVERAGES] assignment of land uses to subcatchments [LOADINGS] initial pollutant loads on subcatchments [BUILDUP] buildup functions for pollutants and land uses [WASHOFF] washoff functions for pollutants and land uses [TREATMENT] pollutant removal functions at conveyance system nodes

[INFLOWS] external hydrograph/pollutograph inflow at nodes [DWF] baseline dry weather sanitary inflow at nodes [RDII] rainfall-dependent I/I information at nodes [HYDROGRAPHS] unit hydrograph data used to construct RDII inflows

[CURVES] x-y tabular data referenced in other sections [TIMESERIES] time series data referenced in other sections [PATTERNS] periodic multipliers referenced in other sections

Figure D-1 Example SWMM project file

Figure D-1 Example SWMM project file (continued from previous page).

Section keywords can appear in mixed lower and upper case. The sections can appear in any arbitrary order in the input file, and not all sections must be present. Each section can contain one or more lines of data. Blank lines may appear anywhere in the file. A semicolon (;) can be used to indicate that what follows on the line is a comment, not data. Data items can appear in any column of a line. Observe how in Figure D-1 these features were used to create a tabular appearance for the data, complete with column headings.

An option is available in the [OPTIONS] section to choose flow units from among cubic feet per second (CFS), gallons per minute (GPM), million gallons per day (MGD), cubic meters per second (CMS), liters per second, (LPS), or million liters per day (MLD). If cubic feet or gallons are chosen for flow units, then US units must be used for all other quantities. If cubic meters or liters are chosen, then metric units must be used for all other quantities. Exceptions are pollutant concentration and Manning’s roughness coefficient (n) which are always expressed in metric units. The default flow units are CFS. A7 — Reference Tables provides a complete listing of measurement units.

A detailed description of the data in each section of the input file will now be given. Each section description begins on a new page. When listing the format of a line of data, mandatory keywords are shown in boldface while optional items appear in parentheses. A list of keywords separated by a slash (YES/NO) means that only one of the words should appear in the data line.

Section: [TITLE]

Purpose: Attaches a descriptive title to the project being analyzed.

Format: Any number of lines may be entered. The first line will be used as a page header in the output report.

Section: [OPTIONS]

Purpose: Provides values for the analysis options that select the process models, the solvers and their closures, the time steps, and reporting.

Format:

Keyword Value

Parameters:

Every keyword below is matched case-insensitively by the parser (OptionsHandler.cpp, handle_options()); only the first value token after the keyword is read. A keyword the parser does not recognise is not an error: it is stored upper-cased in the extension-options map (SimulationOptions::ext_options), a non-fatal "Unknown option keyword" warning is written to the report file, and the value stays available to plugins through swmm_options_get_ext(). An unrecognised value of FLOW_UNITS, INFILTRATION, FLOW_ROUTING, QUALITY_SOLVER, OUTFALL_BACKFLOW_QUALITY or DISPERSION is stored the same way but without a warning; an unrecognised value of any other enumerated keyword is silently ignored and the default stands. Boolean spellings differ by key: the IGNORE_* keys, ALLOW_PONDING, SKIP_STEADY_STATE and WRITE_ABSOLUTE_PATHS take YES, TRUE or 1 as true and anything else as false; FV_COMPACTION, FV_LTS and FV_NODE_FEEDBACK_DT take NO, FALSE, 0 or OFF as false and anything else as true; the remaining switches list their accepted spellings in the Values column.

Three sections carry a keyword spelled DISPERSION, and they mean different things. In [OPTIONS], DISPERSION RWPT or OFF is the switch for random-walk particle dispersion under QUALITY_SOLVER LAGRANGIAN (quality §7.4.1); it takes no coefficient and warns under any other quality solver. In [TRANSPORT_OPTIONS], DISPERSION OFF, FISCHER or a number sets the longitudinal dispersion coefficient of the Eulerian ARD engine, in project length squared per second (quality §7.3.3). In [2D_OPTIONS], DISPERSION is the isotropic species dispersion coefficient of the 2D surface in m²/s, default 0, with negative values refused. (A fourth, [GW_TRANSPORT_OPTIONS] DISPERSION YES or NO, is a switch of the groundwater-transport sections, which are authored but inert.) The table below documents only the [OPTIONS] key.

Units and process models

Keyword	Values	Default	Description
FLOW_UNITS	CFS / GPM / MGD / CMS / LPS / MLD	CFS	Selects the flow unit; a US unit puts every other quantity in US customary units, a metric unit in SI. Concentrations and Manning's n stay metric.
INFILTRATION	HORTON / MOD_HORTON / MODIFIED_HORTON / GREEN_AMPT / MOD_GREEN_AMPT / MODIFIED_GREEN_AMPT / CURVE_NUMBER	HORTON	Selects the subcatchment infiltration model. MOD_HORTON and MOD_GREEN_AMPT are this engine's aliases of the legacy MODIFIED_* spellings.
FLOW_ROUTING	STEADY / NF / KINWAVE / XKINWAVE / KW / EKW / KINEMATIC_WAVE / DYNWAVE / DW / DYNAMIC_WAVE / FV / FINITE_VOLUME / NONE / NO_ROUTING	DYNWAVE	Selects the conveyance routing method; FV is the explicit finite-volume solver (hydraulics Chapter 8). Legacy spellings match as prefixes (STEADYFLOW is STEADY); NONE and NO_ROUTING set IGNORE_ROUTING.
LINK_OFFSETS	DEPTH / ELEVATION	DEPTH	Sets whether link offsets are distances above the node invert (DEPTH) or absolute elevations (ELEVATION).
ALLOW_PONDING	YES / NO	NO	Lets excess water pond atop nodes and re-enter as conditions permit; a node also needs a non-zero Ponded Area for ponding to occur.
IGNORE_RAINFALL	YES / NO	NO	Skips all rainfall and runoff computation; only user-supplied direct and dry-weather inflows are routed.
IGNORE_SNOWMELT	YES / NO	NO	Skips snowmelt computation even when the project defines snow packs.
IGNORE_GROUNDWATER	YES / NO	NO	Skips groundwater computation even when the project defines aquifers.
IGNORE_RDII	YES / NO	NO	Skips rainfall-dependent infiltration and inflow even when unit hydrographs and RDII inflows are supplied.
IGNORE_ROUTING	YES / NO	NO	Computes runoff only, even when the project contains nodes and links.
IGNORE_QUALITY	YES / NO	NO	Skips pollutant washoff, routing and treatment in a project that defines pollutants.

Dates and times

Keyword	Values	Default	Description
START_DATE	MM/DD/YYYY	01/01/2004	Date on which the simulation begins.
START_TIME	HH:MM:SS	00:00:00	Time of day on START_DATE at which the simulation begins.
END_DATE	MM/DD/YYYY	—	Date on which the simulation ends. Required: the engine has no fallback, and a run ending on or before its start is rejected at initialisation.
END_TIME	HH:MM:SS	00:00:00	Time of day on END_DATE at which the simulation ends.
REPORT_START_DATE	MM/DD/YYYY	START_DATE value	Date on which reporting of results begins; when omitted, reporting starts with the simulation.
REPORT_START_TIME	HH:MM:SS	00:00:00	Time of day on REPORT_START_DATE at which reporting begins. Give it together with REPORT_START_DATE; alone it is added to a zero date.
SWEEP_START	MM/DD	1/1	Day of the year on which street sweeping begins.
SWEEP_END	MM/DD	12/31	Day of the year on which street sweeping ends.
DRY_DAYS	number	0	Antecedent days without rainfall before the simulation starts, which seed the initial pollutant buildup.

Time steps

Keyword	Values	Default	Description
ROUTING_STEP	number or HH:MM:SS	20	Routing time step in seconds (fractions allowed) for flows and quality; also the ceiling of the variable dynamic-wave step.
VARIABLE_STEP	number	0.75	Courant safety factor for the variable dynamic-wave step, which never exceeds ROUTING_STEP; 0 fixes the step.
MINIMUM_STEP	number or HH:MM:SS	0.5	Smallest routing step, in seconds, the variable dynamic-wave step may take.
LENGTHENING_STEP	number	0	Time step, in seconds, to which conduits are lengthened to meet the Courant criterion under dynamic wave; 0 lengthens none.
WET_STEP	HH:MM:SS	00:05:00	Runoff time step during rainfall or while water remains ponded on subcatchments.
DRY_STEP	HH:MM:SS	01:00:00	Runoff time step (essentially pollutant buildup) during periods with no rainfall and no ponded water.
RULE_STEP	number or HH:MM:SS	0	Interval, in seconds, at which control rules are evaluated; 0 evaluates them every routing step.

Reporting

Keyword	Values	Default	Description
REPORT_STEP	HH:MM:SS	00:15:00	Interval at which computed results are written to the binary output file.
REPORT_SIGNED_HEADS	YES / TRUE / ON / 1 / NO	NO	Writes the true signed piezometric head to the output HEAD field, needed to see sub-atmospheric TPA heads; NO keeps legacy bit-parity. DEPTH stays floored either way.

Dynamic wave solver

Keyword	Values	Default	Description
MAX_TRIALS	number	8	Maximum trials per time step for the nodal head iteration to converge.
HEAD_TOLERANCE	number	0	Head change between trials, in project length units, below which the step has converged; 0 selects 0.005 ft (0.0015 m).
MIN_SURFAREA	number	0	Numerical stability area for legacy junction depth updates; 0 selects 12.566 ft² (1.167 m²). This is not the authored physical junction StorageArea.
MIN_SLOPE	number	0	Minimum conduit slope in percent; 0 imposes none, though the elevation drop is still floored at 0.001 ft (0.00035 m).
SLOPE_WEIGHTING	YES / NO / TRUE / FALSE / 1 / 0	—	Retired compatibility option with no solver effect. YES and NO also accept legacy prefix matches; other values are rejected. When supplied, the value is retained in the extension-options map and can be read through `swmm_options_get_ext()`.
INERTIAL_DAMPING	NONE / PARTIAL / FULL	PARTIAL	Handling of the momentum inertial terms: kept in full (NONE), reduced toward critical flow and dropped when supercritical (PARTIAL), or dropped (FULL). Hydraulics §3.3.3.
NORMAL_FLOW_LIMITED	SLOPE / FROUDE / BOTH / NEITHER	BOTH	Test that flags supercritical flow to be limited to normal flow: water-surface slope, Froude number, both, or neither. Hydraulics §3.3.4.
NODE_CONTINUITY	EXPLICIT / SEMI_IMPLICIT	EXPLICIT	Node head update: the legacy two-branch formulation, or the unified semi-implicit one that folds flow gradients into the depth update. Hydraulics §3.5.
ANDERSON_ACCEL	YES / TRUE / 1 / NO	NO	Accelerates the Picard head iteration with depth-2 Anderson mixing, typically cutting trials by 25 to 50 percent. Hydraulics §3.6.

Pressurisation and friction

Keyword	Values	Default	Description
SURCHARGE_METHOD	EXTRAN / SLOT / DYNAMIC_SLOT / TPA	EXTRAN	Surcharge treatment under dynamic wave: the EXTRAN algorithm, a Preissmann slot, a dynamic slot with modeller-set celerity (hydraulics §3.3.9), or the two-component pressure approach (§3.3.11; TPA only) Experimental
TPA_CELERITY	number	100	Acoustic celerity, in project length units per second, that sizes the constant slot width under SURCHARGE_METHOD TPA. Hydraulics §3.3.11. Experimental
DPS_CELERITY	number	25.0	Target pressure-wave celerity in m/s of the dynamic slot; lower values allow larger steps but reduce transient fidelity. Hydraulics §3.3.9.
DPS_ALPHA	number	3.0	Surcharge shock parameter (at least 2) of the dynamic slot; larger values give a bigger celerity shock at the mixed-flow transition. Hydraulics §3.3.9.
DPS_DECAY_TIME	number	0.5	Time, in seconds, for the dynamic slot's Preissmann number to decay toward 1; shorter transitions faster but may oscillate. Hydraulics §3.3.9.
FORCE_MAIN_EQUATION	H-W / HW / HAZEN-WILLIAMS / D-W / DW / DARCY-WEISBACH	H-W	Friction-loss equation for pressurised flow in Circular Force Main conduits: Hazen-Williams or Darcy-Weisbach.
UNSTEADY_FRICTION	NONE / VITKOVSKY	NONE	Adds the Vítkovský-type unsteady friction term to the momentum equation in both the dynamic wave and finite-volume solvers. Hydraulics §3.3.12 and §8.5.4.
UF_K3	number	0.015	Brunone-type coefficient k3 of the unsteady friction term; read only when UNSTEADY_FRICTION is not NONE. Literature range 0.005 to 0.020.

Finite-volume routing (FV_*)

These keys are read only under FLOW_ROUTING FV; under any other routing model they are accepted and inert, so switching FLOW_ROUTING never invalidates a file (hydraulics §8.9).

Keyword	Values	Default	Description
FV_CELL_LENGTH	number	0	Target cell length in project length units; 0 sets no target and each conduit gets FV_MIN_CELLS cells. Hydraulics §8.3.
FV_MIN_CELLS	number	4	Floor on cells per conduit, with or without a length target; a single cell under-conveys at every manhole. Hydraulics §8.3.
FV_CFL	number	0.5	Courant number bounding the explicit substep. Hydraulics §8.5.5.
FV_RIEMANN	HLL / HLLC	HLLC	Face flux solver; HLLC resolves the contact wave that carries advected scalars, HLL is a debugging baseline. Hydraulics §8.5.3.
FV_ORDER	1 / 2	1	Spatial order; 2 enables MUSCL-Hancock reconstruction with the limiter of FV_LIMITER. Hydraulics §8.5.7.
FV_LIMITER	MINMOD / VANLEER / SUPERBEE	MINMOD	Slope limiter used with FV_ORDER 2; MINMOD is most robust, SUPERBEE sharpest. Hydraulics §8.5.7.
FV_SCALAR_SCHEME	UPWIND / MUSCL / QUICKEST_ULTIMATE / QUICKEST	MUSCL	Reconstruction of the advected scalar field on the finite-volume mesh. Hydraulics §8.8.
FV_TIME_INTEGRATION	EULER / RK2	EULER	Time integrator: forward Euler or SSP-RK2 (Heun); RK2 disables local time stepping. Hydraulics §8.5.5.
FV_SLOT_CELERITY	number	100	Pressurised wave celerity in project length units per second; sets the slot width and doubles as the TPA acoustic celerity. Hydraulics §8.4.1.
FV_PRESSURIZED_IMPLICIT	YES / TRUE / ON / 1 / NO	NO	Integrates the slot's acoustic pair implicitly on pressurised cells, removing the celerity from the time-step law; CPU only, local time stepping stands down. Hydraulics §8.4.4. Experimental
FV_PRESSURE_CLOSURE	SLOT / TPA	SLOT	Pressurisation closure: the Preissmann slot, or the two-component pressure approach that allows sub-atmospheric full-pipe flow. Hydraulics §8.4.5. Experimental
FV_DISPERSION	number	0	Longitudinal dispersion coefficient in project length squared per second; 0 disables it. Accepted but inert until finite-volume transport is connected; non-zero warns at open. Hydraulics §8.8.
FV_STRUCTURE_COUPLING	SUBSTEP / ROUTING_STEP	SUBSTEP	Cadence at which pump, orifice, weir and outlet flows and outfall stages refresh: every substep, or once per routing step. Hydraulics §8.6.3.
FV_COMPACTION	YES / NO / FALSE / 0 / OFF	YES	Skips dry, inactive parts of the network; results-transparent by contract. Hydraulics §8.5.9.
FV_LTS	YES / NO / FALSE / 0 / OFF	YES	Local time stepping: stiff cells substep at their own power-of-two tier; NO forces one global substep. Hydraulics §8.5.6.
FV_LTS_MAX_TIERS	number	6	Cap on the local-time-stepping tier spread; 6 allows a 64-fold spread, and the hard ceiling is 8. Hydraulics §8.5.6.
FV_NODE_FEEDBACK_DT	YES / NO / FALSE / 0 / OFF	NO	Bounds the explicit step by the algebraic-junction feedback limit at pressurised junctions; removes oscillation at 10 to 14 times the wall cost. Hydraulics §8.6.1.
FV_CFL_CENSUS_INTERVAL	number	1	Substeps between full Courant censuses; 1 recomputes every substep. Hydraulics §8.5.5.
FV_BACKEND	CPU / AUTO / OMP / CUDA / HIP / SYCL	AUTO	Kernel backend; AUTO tries plugins above FV_MIN_PARALLEL_CELLS and otherwise stays on the CPU.
FV_MIN_PARALLEL_CELLS	number	20000	Cell count below which FV_BACKEND AUTO stays on the CPU.

Water quality and transport

Keyword	Values	Default	Description
QUALITY_SOLVER	LEGACY / EULERIAN_ARD / ARD / LAGRANGIAN / LARD	LEGACY	Selects the transport engine: legacy tanks-in-series, Eulerian ARD on fixed cells, or Lagrangian parcels (LARD). Quality §7.1.
QUALITY_STEP	number or HH:MM:SS	0	LARD transport substep in seconds; each routing step splits into equal substeps. 0 follows ROUTING_STEP; warns under other solvers. Quality §7.4.
MAX_SEGMENTS_PER_LINK	number	100	Cap on LARD parcels per link; the oldest parcels merge when it is reached. Clamped to at least 2; LARD only. Quality §7.4.
DISPERSION	RWPT / OFF / NONE	OFF	Random-walk particle dispersion under QUALITY_SOLVER LAGRANGIAN; warns under other solvers. Distinct from the [TRANSPORT_OPTIONS] and [2D_OPTIONS] keys. Quality §7.4.1.
RWPT_SEED	number	0	Deterministic seed of the RWPT counter random generator; the same seed reproduces a run bit-for-bit at any thread count. Quality §7.4.1.
WATER_AGE	ON / YES / OFF / NO	OFF	Tracks transported water age as the reserved species `__WATER_AGE__`; per-source initial ages come from [WATER_AGE_SOURCES]. Quality §9.2.
OUTFALL_BACKFLOW_QUALITY	LAST / ZERO	LAST	Quality carried by reverse flow at outfalls: the held last mixed state (legacy), or a fresh zero boundary for every pollutant and water age.

Heat transport

Keyword	Values	Default	Description
HEAT_TRANSPORT	ON / YES / OFF / NO	OFF	Transports temperature as the reserved species `__TEMPERATURE__`; inlet temperatures come from [HEAT_SOURCES]. Quality §9.3.
WATER_DENSITY	number	1000.0	Water density in kg/m³, which weights surface heat fluxes against advected heat. Quality §9.3.9.
WATER_SPECIFIC_HEAT_CAPACITY	number	4184.0	Specific heat capacity of water in J/kg/°C used to convert surface heat fluxes into temperature change. Quality §9.3.9.
WIND_FUNC_COEFF_A	number	1.505e-8	Constant term a of the wind function f(w) = a + b·w in the latent-heat flux (Dunne and Leopold 1978). Quality §9.3.4.
WIND_FUNC_COEFF_B	number	1.6e-8	Wind-speed coefficient b of the wind function f(w) = a + b·w in the latent-heat flux. Quality §9.3.4.
PRESSURE_RATIO	number	1.0	Ratio of site to sea-level atmospheric pressure that corrects the Bowen ratio in the sensible-heat flux. Quality §9.3.5.

2D, coordinate reference and files

Keyword	Values	Default	Description
IGNORE_2D	YES / NO	NO	Disables the 2D surface-routing module even when the model carries a mesh, so the model runs 1D-only without stripping its mesh sections.
CRS	EPSG code or quoted PROJ string	—	Coordinate reference system of the model geometry, applied to [COORDINATES], [VERTICES] and [POLYGONS]; readable through swmm_spatial_get_crs(). Empty when omitted.
WRITE_ABSOLUTE_PATHS	YES / NO	NO	Makes the .inp writer emit external-file paths absolute instead of rebased relative to the saved file; for tools that reject relative paths.

Miscellaneous

Keyword	Values	Default	Description
THREADS	number	1	OpenMP thread count for dynamic-wave and 2D loops; 0 resolves to the runtime maximum, and larger values oversubscribe with a warning.
SKIP_STEADY_STATE	YES / NO	NO	Skips routing during steady periods, reusing the last flows, when system flow and lateral inflows change by less than SYS_FLOW_TOL and LAT_FLOW_TOL.
SYS_FLOW_TOL	number	5	Maximum percent difference between total system inflow and outflow for SKIP_STEADY_STATE to take effect.
LAT_FLOW_TOL	number	5	Maximum percent difference between current and previous lateral inflows for SKIP_STEADY_STATE to take effect.

Retired keywords

Keyword	Status	Behaviour today
FV_NODE_COUPLING	Retired	Parsed; the value EXPLICIT warns and is treated as SEMI_IMPLICIT (storage nodes are always coupled semi-implicitly); any other value is silently ignored.
FV_NODE_DT	Retired	Parsed; the value NONE warns and is treated as STABILITY (the node accuracy bound is always armed); any other value is silently ignored.
FV_NODE_PICARD	Retired	Parsed; a value above 1 warns and is treated as 1 (the semi-implicit node correction is always a single sweep); 1 or less is silently accepted.
FV_NODE_CELL_COUPLING	Retired	Accepted and silently ignored; junctions are always algebraic interfaces (hydraulics §8.6.1).
FV_JUNCTION_MODEL	Retired	Accepted and silently ignored; the BUCKET junction model was removed in favour of the algebraic interface (hydraulics §8.6.1).
VIRTUAL_JUNCTION_MOMENTUM	Retired	Parsed; FULL warns and is treated as BASIC (its cross-junction momentum term was not mass conserving); every value maps to BASIC and the key is never written back.
COMPATIBILITY	Retired	Accepted and silently ignored; a legacy SWMM compatibility flag with no effect in this engine.

Section: [REPORT]

Purpose: Describes the contents of the report file that is produced.

Formats: DISABLED YES / NO INPUT YES / NO CONTINUITY YES / NO FLOWSTATS YES / NO CONTROLS YES / NO LINK_STEPS YES / NO SUBCATCHMENTS ALL / NONE / <list of subcatchment names> NODES ALL / NONE / <list of node names> LINKS ALL / NONE / <list of link names> LID Name Subcatch Fname

Remarks: Setting DISABLED to YES disables all reporting (except for error and warning messages) regardless of what other reporting options are chosen. The default is NO. INPUT specifies whether or not a summary of the input data should be provided in the output report. The default is NO. CONTINUITY specifies if continuity checks should be reported or not. The default is YES. FLOWSTATS specifies whether summary flow statistics should be reported or not. The default is YES. CONTROLS specifies whether all control actions taken during a simulation should be listed or not. The default is NO. LINK_STEPS (OpenSWMM extension) adds a Conduit Time Step Summary table: for each reported conduit, the minimum, time-weighted average and maximum local time step, the percent of time spent in each of five step ranges below the routing step ((RS/2, RS], (RS/4, RS/2], ..., up to RS/16), and the percent of routing steps in which both end nodes converged. Under DYNWAVE the step is the CFL step each conduit allows (Courant factor applied, capped at the routing step); all conduits still advance at the global step, and dry conduits are not sampled. Under FV it is the local time step each conduit actually took (its finest cell under local time stepping, otherwise the global substep), and the convergence column is blank because the scheme is explicit. Other routing methods print "Not available". The default is NO; the key is not written when exporting to SWMM 5. SUBCATCHMENTS gives a list of subcatchments whose results are to be reported. The default is NONE. NODES gives a list of nodes whose results are to be reported. The default is NONE. LINKS gives a list of links whose results are to be reported. The default is NONE. LID specifies that the LID control Name in subcatchment Subcatch should have a detailed performance report for it written to file Fname. The SUBCATCHMENTS, NODES, LINKS, and LID lines can be repeated multiple times.

Section: [FILES]

Purpose: Identifies optional interface files used or saved by a run.

Formats: USE / SAVE RAINFALL Fname
USE / SAVE RUNOFF Fname
USE HOTSTART Fname SAVE HOTSTART Fname (Date Time) (LEGACY / NATIVE) USE / SAVE RDII Fname USE INFLOWS Fname SAVE OUTFLOWS Fname

Parameters: Fname is the name of an interface file. Date Time is the optional date (month/day/year) and time (hours:minutes:seconds) at which a Hot Start file is saved: the file is written from the state at the end of the first time step that reaches that moment, and not at all if the run ends first. Without it the file is saved at the end of the run. LEGACY / NATIVE (OpenSWMM extension) is the optional file format of a saved Hot Start file. LEGACY is the EPA SWMM 5 format, which holds subcatchment, node and link state; OpenSWMM applies all of it when it reads one. NATIVE is the OpenSWMM format, which also holds water age, reaction species, LID units at storage nodes and the 2D aquifer, but not link control settings, node lateral inflows or subcatchment buildup — see CHAPTER 3 - Files and Command-Line Operation. Without the keyword a SWMM 5 file is written, or a native one when the model has LID units at storage nodes.

Remarks: Refer to CHAPTER 3 - Files and Command-Line Operation for a description of interface files. Rainfall, Runoff, and RDII files can either be used or saved in a run, but not both. A run can both use and save a Hot Start file (with different names). USE HOTSTART reads either format, recognising it from the file itself. The format keyword must follow the date and time when both are given. Any other word in its place is ignored with a warning, and the default format is used. A row with exactly a date after the file name and one more item must give a valid date and time, or it is an error (ERROR 213), as in EPA SWMM. EPA SWMM 5 ignores the keyword, so a row carrying it still opens there, but it then also ignores a date and time on the same row and saves at the end of the run; export to SWMM 5 omits the keyword. A NATIVE file cannot be read by EPA SWMM 5. A GeoPackage stores the format choice but embeds only SWMM 5 format Hot Start files; it gives them back unchanged, subcatchment state included. Enclose the external file name in double quotes if it contains spaces and include its full path if it resides in a different directory than the SWMM input file.

Section: [RAINGAGES]

Purpose: Identifies each rain gage that provides rainfall data for the study area.

Formats: Name Form Intvl SCF TIMESERIES Tseries Name Form Intvl SCF FILE Fname (Sta Units)

Parameters: Name name assigned to rain gage. Form form of recorded rainfall, either INTENSITY, VOLUME or CUMULATIVE. Intvl time interval between gage readings in decimal hours or hours:minutes format (e.g., 0:15 for 15-minute readings). SCF snow catch deficiency correction factor (use 1.0 for no adjustment). Tseries name of a time series in the [TIMESERIES] section with rainfall data. Fname name of an external file with rainfall data. Rainfall files are discussed in CHAPTER 3 - Files and Command-Line Operation. Sta name of the recording station in a user-prepared formatted rain file. Units rain depth units for the data in a user-prepared formatted rain file, either IN (inches) or MM (millimeters).

Remarks: Enclose the external file name in double quotes if it contains spaces and include its full path if it resides in a different directory than the SWMM input file. The station name and depth units entries are only required when using a user-prepared formatted rainfall file.

New in OpenSWMM v6: A multi-column rain file can be referenced by appending a colon and column name to the file path, e.g. FILE "rain.csv:EAST_GAGE". The engine opens the file, locates the column whose header matches the given name (case-insensitive), and reads the rainfall values from that column; an empty column name selects the first data column. Comma- and tab-delimited files with a header row are supported, as is the PCSWMM .tsf format (tab-delimited, IDs: header row, 12-hour AM/PM date-times) — the format is detected automatically from the file's contents. This allows a single file to supply data for multiple rain gages (and named time series — see the [TIMESERIES] section); each such file is read from disk only once per model open, regardless of how many gages or series reference it.

Section: [EVAPORATION]

Purpose: Specifies how daily potential evaporation rates vary with time for the study area.

Formats: CONSTANT evap MONTHLY e1 e2 e3 e4 e5 e6 e7 e8 e9 e10 e11 e12 TIMESERIES Tseries TEMPERATURE FILE (p1 p2 p3 p4 p5 p6 p7 p8 p9 p10 p11 p12) RECOVERY patternID DRY_ONLY NO / YES

Parameters: evap constant evaporation rate (in/day or mm/day). e1 evaporation rate in January (in/day or mm/day). ... e12 evaporation rate in December (in/day or mm/day). Tseries name of a time series in the [TIMESERIES] section with evaporation data. p1 pan coefficient for January. ... p12 pan coefficient for December. patID name of a monthly time pattern.

Remarks: Use only one of the above formats (CONSTANT, MONTHLY, TIMESERIES, TEMPERATURE, or FILE). If no [EVAPORATION] section appears, then evaporation is assumed to be 0. TEMPERATURE indicates that evaporation rates will be computed from the daily air temperatures contained in an external climate file whose name is provided in the [TEMPERATURE] section. This method also uses the site’s latitude, which can also be specified in the [TEMPERATURE] section. FILE indicates that evaporation data will be read directly from the same external climate file used for air temperatures as specified in the [TEMPERATURE] section. Supplying monthly pan coefficients for these data is optional. RECOVERY identifies an optional monthly time pattern of multipliers used to modify infiltration recovery rates during dry periods. For example, if the normal infiltration recovery rate was 1% during a specific time period and a pattern factor of 0.8 applied to this period, then the actual recovery rate would be 0.8%. DRY_ONLY determines if evaporation only occurs during periods with no precipitation. The default is NO. The evaporation rates provided in this section are potential rates. The actual amount of water evaporated will depend on the amount available as a simulation progresses.

Section: [TEMPERATURE]

Purpose:
Specifies daily air temperatures, monthly wind speed, and various snowmelt parameters for the study area. Required only when snowmelt is being modeled or when evaporation rates are computed from daily temperatures or are read from an external climate file.

Formats: TIMESERIES Tseries FILE Fname (Start) (Units) WINDSPEED MONTHLY s1 s2 s3 s4 s5 s6 s7 s8 s9 s10 s11 s12 WINDSPEED FILE SNOWMELT Stemp ATIwt RNM Elev Lat DTLong ADC IMPERVIOUS f.0 f.1 f.2 f.3 f.4 f.5 f.6 f.7 f.8 f.9 ADC PERVIOUS f.0 f.1 f.2 f.3 f.4 f.5 f.6 f.7 f.8 f.9

Parameters: Tseries name of a time series in the [TIMESERIES] section with temperature data. Fname name of an external Climate file with temperature data. Start date to begin reading from the file in month/day/year format (default is the beginning of the file). Units temperature units for GHCN files (C10 for tenths of a degree C (the default), C for degrees C or F for degrees F. s1 average wind speed in January (mph or km/hr). ... s12 average wind speed in December (mph or km/hr). Stemp air temperature at which precipitation falls as snow (deg F or C). ATIwt antecedent temperature index weight (default is 0.5). RNM negative melt ratio (default is 0.6). Elev average elevation of study area above mean sea level (ft or m) (default is 0). Lat latitude of the study area in degrees North (default is 50). DTLong correction, in minutes of time, between true solar time and the standard clock time (default is 0). f.0 fraction of area covered by snow when ratio of snow depth to depth at 100% cover is 0 ... f.9 fraction of area covered by snow when ratio of snow depth to depth at 100% cover is 0.9.

Remarks: Use the TIMESERIES line to read air temperature from a time series or the FILE line to read it from an external Climate file. Climate files are discussed in CHAPTER 3 - Files and Command-Line Operation. If neither format is used, then air temperature remains constant at 70 degrees F. Enclose the Climate file name in double quotes if it contains spaces and include its full path if it resides in a different directory than the SWMM input file. Temperatures supplied from NOAA's latest Climate Data Online GHCN files should have their units (C or F) specified. Older versions of these files listed temperatures in tenths of a degree C (C10). An asterisk can be entered for the Start date if it defaults to the beginning of the file. Wind speed can be specified either by monthly average values or by the same Climate file used for air temperature. If neither option appears, then wind speed is assumed to be 0. Separate Areal Depletion Curves (ADC) can be defined for impervious and pervious subareas. The ADC parameters will default to 1.0 (meaning no depletion) if no data are supplied for a particular type of subarea.

Energy-balance snow and shared radiation

The following additional [TEMPERATURE] rows configure UEB snow and the radiation forcing shared with heat transport:

SNOWMELT_MODEL  DEGREE_DAY / UEB
SNOW_STEP      Step
SITE           Latitude Longitude Timezone Elevation
SHORTWAVE      COMPUTED / FILE
SHORTWAVE      TIMESERIES Series
LONGWAVE       COMPUTED / FILE
LONGWAVE       TIMESERIES Series
MET_FILE       "Path"

Key	Default	Meaning and units
SNOWMELT_MODEL	DEGREE_DAY	Shared snow formulation; an individual [SNOWPACKS] UEB row can override it.
SNOW_STEP	3600	Snow update interval in seconds or HH:MM[:SS], from 1 to 21600 seconds. Mesh snow can choose a separate interval in [2D_SNOW_OPTIONS].
SITE	legacy climate/solar site	Latitude in degrees north, longitude in degrees east, UTC offset in hours, and elevation in metres in both US and SI projects. Bounds are ±90 degrees latitude, ±180 degrees longitude, ±14 hours and -500 to 10000 m elevation. An explicit SITE takes precedence over conflicting legacy site values and emits a warning.
SHORTWAVE	COMPUTED	Incoming horizontal shortwave radiation; a named series supplies W/m². FILE uses the hourly MET_FILE.
LONGWAVE	COMPUTED	Incoming longwave radiation; a named series supplies W/m². FILE uses the hourly MET_FILE.
MET_FILE	none	Hourly meteorology path, resolved relative to the input file. Quote a path containing spaces.

MET_FILE is distinct from the legacy daily climate FILE row. Each record has seven fields: MM/DD/YYYY HH:00 Temperature_C RH_percent Wind_m/s Shortwave_W/m2 Longwave_W/m2. Records must be finite, consecutive, unique whole hours and cover the simulation interval; each record describes the following hour. These quantities always use the displayed SI units, independent of project units. An hourly MET_FILE supplies all five quantities and takes precedence over other air-temperature and radiation selectors while it is active. A radiation FILE selector requires MET_FILE. Named radiation series must exist in [TIMESERIES].

Computed shortwave uses the Bristow–Campbell parameters in [UEB_OPTIONS]. Forcing is averaged over the snow interval; UEB snow site parameters are supplied by [SNOWPACKS]. The legacy TIMESERIES, FILE, WINDSPEED, SNOWMELT and ADC rows remain available.

Section: [UEB_OPTIONS]

Purpose: Sets shared Utah Energy Balance snow parameters and computed-radiation coefficients. These rows do not by themselves select UEB; use SNOWMELT_MODEL in [TEMPERATURE] or a per-pack model in [SNOWPACKS].

Formats:

SURFACE_TEMP  MODIFIED_FORCE_RESTORE / EQUILIBRIUM
PRECIP_SPLIT  UEB / DIVT
Key           Value
BC_MONTHLY    Month Range

Key	Default	Meaning and units
SURFACE_TEMP	MODIFIED_FORCE_RESTORE	Surface-temperature scheme; EQUILIBRIUM selects the alternative equilibrium solve.
PRECIP_SPLIT	UEB	UEB partitions precipitation between the TB and TR temperatures. DIVT uses the legacy SNOWMELT division temperature for an all-snow/all-rain split.
Z0	0.01	Aerodynamic roughness length (m).
ZM	2	Measurement height above the surface (m); must exceed Z0.
KS	0.02	Equilibrium heat-exchange conductance (m/h).
KSAT	200	Snow drainage conductivity (m/h).
LC	0.02	Liquid-water retention parameter (dimensionless).
DE	0.1	Thermally active soil depth (m).
RHO_S	200	Snow density (kg/m³), greater than zero and less than 917.
RHO_G	1700	Soil density (kg/m³).
CG	2.09	Soil specific heat capacity (kJ/(kg K)).
LAMBDA_S	0.33	Snow thermal conductivity (kJ/(m K h)).
LAMBDA_G	6.5	Soil thermal conductivity (kJ/(m K h)).
OMEGA_LF	0.0654	Low-frequency parameter for modified force restore (1/h).
R	1	Modified force-restore amplitude factor (dimensionless).
FSTAB	1	Atmospheric stability factor (fraction from 0 to 1).
TR	3	Temperature at which precipitation is entirely rain under PRECIP_SPLIT UEB (°C); must exceed TB.
TB	-1	Temperature at which precipitation is entirely snow under PRECIP_SPLIT UEB (°C); must exceed absolute zero.
ABG	0.25	Bare-ground albedo (fraction from 0 to 1).
ALPHA_VO	0.85	New-snow visible albedo (fraction from 0 to 1).
ALPHA_IRO	0.65	New-snow infrared albedo (fraction from 0 to 1).
EPSILON	0.99	Snow emissivity (fraction from 0 to 1).
DNEWS	0.002	New-snow depth scale for resetting snow age (m water equivalent).
R3	0.03	Snow-age dust parameter (nonnegative, dimensionless).
CV	0.2	Visible snow-age coefficient (fraction from 0 to 1).
CIR	0.5	Infrared snow-age coefficient (fraction from 0 to 1).
BC_A	0.8	Bristow–Campbell maximum transmittance, greater than zero and at most 1.
BC_C	2.4	Positive Bristow–Campbell exponent.
BC_MONTHLY	unspecified	Month (integer 1–12) and positive daily temperature range in °C, at most 100. Supply one row per month to override that month's range.

Remarks: All parameter units are fixed as listed, including in US projects; the conductivity and conductance units retain the UEB reference model's hour-based convention. Every numeric value must be finite. Lengths, densities, heat capacities, thermal conductivities, KS, OMEGA_LF and R must be positive; KSAT, DNEWS and R3 may be zero. LC must be nonnegative and less than 1000/RHO_S - 1000/917. The complete parameter set is validated before initialization.

An unspecified BC_MONTHLY value uses the available daily temperature range; it does not invent a monthly climatology. Unknown keys or extra fields are errors. The input writer emits only values that differ from their defaults and explicitly supplied monthly ranges.

Example:

[UEB_OPTIONS]
SURFACE_TEMP MODIFIED_FORCE_RESTORE
PRECIP_SPLIT UEB
BC_A 0.8
BC_C 2.4
BC_MONTHLY 1 10

This section has no counterpart in SWMM 5.

Section: [ADJUSTMENTS]

Purpose: Specifies optional monthly adjustments to be made to temperature, evaporation rate, rainfall intensity and hydraulic conductivity in each time period of a simulation.

Formats: TEMPERATURE t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 EVAPORATION e1 e2 e3 e4 e5 e6 e7 e8 e9 e10 e11 e12 RAINFALL r1 r2 r3 r4 r5 r6 r7 r8 r9 r10 r11 r12 CONDUCTIVITY c1 c2 c3 c4 c5 c6 c7 c8 c9 c10 c11 c12

Parameters: t1..t12 adjustments to temperature in January, February, etc., as plus or minus degrees F (degrees C). e1..e12 adjustments to evaporation rate in January, February, etc., as plus or minus in/day (mm/day). r1..r12 multipliers applied to precipitation rate in January, February, etc. c1..c12 multipliers applied to soil hydraulic conductivity in January, February, etc. used in either Horton or Green-Ampt infiltration. Remarks: The same adjustment is applied for each time period within a given month and is repeated for that month in each subsequent year being simulated.

Section: [SUBCATCHMENTS]

Purpose: Identifies each subcatchment within the study area. Subcatchments are land area units which generate runoff from rainfall.

Format: Name Rgage OutID Area Imperv Width Slope Clength (Spack)

Parameters: Name name assigned to the subcatchment. Rgage name of a rain gage in the [RAINGAGES] section assigned to the subcatchment. OutID name of the node or subcatchment that receives runoff from the subcatchment. Area area of the subcatchment (acres or hectares). Imperv percentage of the subcatchment’s area that is impervious. Width characteristic width of the subcatchment (ft or meters). Slope the subcatchment’s slope (percent). Clength total curb length (any length units) used to describe pollutant buildup. Use 0 if not applicable. Spack optional name of a snow pack object (from the [SNOWPACKS] section) that characterizes snow accumulation and melting over the subcatchment.

Section: [SUBAREAS]

Purpose: Supplies information about pervious and impervious areas for each subcatchment. Each subcatchment can consist of a pervious subarea, an impervious subarea with depression storage, and an impervious subarea without depression storage.

Format: Subcat Nimp Nperv Simp Sperv Zero RouteTo (Routed)

Parameters: Subcat subcatchment name. Nimp Manning's coefficient (n) for overland flow over the impervious subarea. Nperv Manning's coefficient (n) for overland flow over the pervious subarea. Simp depression storage for the impervious subarea (inches or mm). Sperv depression storage for the pervious subarea (inches or mm). Zero percent of impervious area with no depression storage. RouteTo IMPERVIOUS if pervious area runoff runs onto impervious area, PERVIOUS if impervious runoff runs onto pervious area, or OUTLET if both areas drain to the subcatchment's outlet (default = OUTLET). Routed percent of runoff routed from one type of area to another (default = 100).

Section: [INFILTRATION]

Purpose: Supplies infiltration parameters for each subcatchment. Rainfall lost to infiltration only occurs over the pervious subarea of a subcatchment.

Format: Subcat p1 p2 p3 (p4 p5) (Method)

Parameters: Subcat subcatchment name. Method either HORTON, MODIFIED_HORTON, GREEN_AMPT, MODIFIED_GREEN_AMPT, or CURVE_NUMBER. If not specified then the infiltration method supplied in the [OPTIONS] section is used. For Horton and Modified Horton Infiltration: p1 maximum infiltration rate on the Horton curve (in/hr or mm/hr). p2 minimum infiltration rate on the Horton curve (in/hr or mm/hr). p3 decay rate constant of the Horton curve (1/hr). p4 time it takes for a fully saturated soil to dry (days). p5 maximum infiltration volume possible (0 if not applicable) (in or mm). For Green-Ampt and Modified Green-Ampt Infiltration: p1 soil capillary suction (in or mm). p2 soil saturated hydraulic conductivity (in/hr or mm/hr). p3 initial soil moisture deficit (porosity minus moisture content) (fraction). For Curve-Number Infiltration: p1 SCS Curve Number. p2 no longer used. p3 time it takes for a fully saturated soil to dry (days).

Section: [LID_NODES]

A LID node remains an ordinary storage node. Assign a compatible BC, RG, IT, PP, or NODE control in [LID_NODES] using Node Control InitialSaturationPercent [BOTTOM CURRENT|SEALED|MESH_AQUIFER]. Omitting the optional bottom fields selects CURRENT. The supported routing formulation is FLOW_ROUTING DYNWAVE. The storage's maximum depth must equal the sum of the physical layer thicknesses, converted to the node's length units.

BOTTOM MESH_AQUIFER is supported for a NODE control with an enabled [LID_RICHARDS] profile and a resolved [2D_AQUIFER_NODE] bed on the active mesh aquifer. Accepted bottom water is exchanged with that groundwater owner. When coupled 2D heat and ground-column conduction are enabled, each physical LID layer has persistent heat capacity and energy, configured vertical layer conduction, and a reciprocal bottom contact with the soil column. The signed contact energy is included in the mesh heat results when HEAT is selected. The CURRENT and SEALED bottom modes retain their existing non-mesh ownership behavior.

A NODE control contains any number of ordered physical layers, written from top to bottom. MEDIA and AGGREGATE may repeat without a fixed layer limit. SURFACE is optional and first; BOTTOM is optional and last.

[LID_CONTROLS]
Column NODE
Column SURFACE    6  0.1
Column MEDIA     12  0.45  0.20  0.08  2  10  3
Column MEDIA      6  0.40  0.25  0.10  1   8  3
Column AGGREGATE  6  0.40  100
Column BOTTOM     0.5  0
[LID_NODES]
S Column 10
[LID_NODE_OUTLETS]
Underdrain 4 BOTTOM
Overflow   1 BOTTOM

For US models this example requires a 2.5-ft storage maximum depth. Layer thickness and suction use inches (US) or millimetres (SI); conductivities use inches/hour or millimetres/hour. SURFACE parameters are thickness and vegetation fraction. MEDIA parameters are thickness, porosity, field capacity, wilting point, saturated conductivity, conductivity slope, and suction. AGGREGATE parameters are thickness, porosity, conductivity. BOTTOM specifies native-soil seepage and clogging factor and has no thickness or layer number. Standard-control storage void ratios are converted to porosity as e / (1 + e).

Section: [LID_NODE_OUTLETS]

Outlet anchors use one-based physical layer numbers and TOP or BOTTOM. The link must have exactly one LID endpoint. Input mismatches between the anchor and authored offset produce a warning; layer edits through the API synchronize the offset and storage maximum depth. A link between two LID nodes can use ordinary explicit offsets without an anchor.

Moisture is discretized into five cells per MEDIA layer, with a separate mobile hydraulic volume. Transfers between these stores conserve water. Reported node volume includes both stores. Positive lateral inflow enters the top of the profile; connected links exchange water at their offsets. Supply rainfall through a contributing subcatchment or an external inflow; these sections do not select a rain gage for direct rainfall on storage. Native hotstarts retain cell moisture and clogging history. INP and GeoPackage save the ordered definitions and anchors. SWMM5-compatible INP export omits these extensions with warnings and leaves plain storage nodes.

For storage-node MEDIA, conductivity slope is dimensionless and nonnegative: K = Ksat * exp(-slope * (porosity - theta)) above field capacity. A zero slope is valid. SURFACE-to-first-MEDIA entry uses modified Green–Ampt, with accepted infiltration history reconciled to backwater wetting and remaining moisture after recession. It is not an intercell matric-gradient or full Richards-equation solution. See CHAPTER 6 — Storage-node LIDs: Implementation and Interfaces and 2.1.4.1 Layered LIDs on storage nodes for the formulation and V10 restart behavior.

Section: [LID_RICHARDS]

Purpose: Selects the optional Richards 1D flow model and defines explicit retention materials for a NODE control from [LID_CONTROLS]. The existing storage-node flow formulation remains the default when no OPTIONS row enables Richards.

Formats:

Control OPTIONS CellsPerPorousLayer AbsTol RelTol MaxInternalStepSeconds

Control PhysicalLayer ResidualTheta Alpha n l Ss

Parameters: Control name of a NODE control with ordered physical layers. CellsPerPorousLayer integer from 1 to 256; numerical cells in each MEDIA or AGGREGATE layer, independent of physical layer count. AbsTol, RelTol positive finite absolute and relative time-integration tolerances, applied to complete water storage divided by geometric volume. MaxInternalStepSeconds positive finite maximum internal solver step, in seconds. PhysicalLayer one-based layer index from top to bottom; must identify MEDIA or AGGREGATE. ResidualTheta residual water content; nonnegative and below porosity, and below the MEDIA wilting point. Alpha positive van Genuchten retention parameter, in inverse metres. n van Genuchten exponent; greater than 1. l nonnegative Mualem conductivity exponent. Ss positive specific storage, in inverse metres.

Remarks: An OPTIONS row enables Richards for the control. Every porous layer needs an explicit material row; SURFACE and BOTTOM have no retention rows. Duplicate OPTIONS or material rows are errors. Alpha and Ss use inverse metres in both US and SI projects; the usual project units still apply to layer thickness and saturated conductivity. Retained material rows do not alone enable Richards.

Use Dynamic Wave routing. Runtime coupling to an active 2D aquifer bed, water age, heat and MSX is not yet supported for Richards nodes and is rejected at initialization. See CHAPTER 6 — Storage-node LIDs: Implementation and Interfaces for an input example, numerical formulation, persistence and validation limits.

Section: [LID_CONTROLS]

Purpose: Defines scale-independent LID controls that can be deployed within subcatchments.

Formats: Name Type followed by one or more of the following lines depending on Type: Name SURFACE StorHt VegFrac Rough Slope Xslope Name SOIL Thick Por FC WP Ksat Kcoeff Suct Name PAVEMENT Thick Vratio FracImp Perm Vclog (Treg Freg) Name STORAGE Height Vratio Seepage Vclog (Covrd) Name DRAIN Coeff Expon Offset Delay (Hopen Hclose Qcrv) Name DRAINMAT Thick Vratio Rough Name REMOVALS Pollut Rmvl Pollut Rmvl ...

Parameters: Name name assigned to LID process. Type BC for bio-retention cell; RG for rain garden; GR for green roof; IT for infiltration trench; PP for permeable pavement; RB for rain barrel; RD for rooftop disconnection; VS for vegetative swale. Pollut name of a pollutant Rmvl the percent removal the LID achieves for the pollutant (several pollutant removals can be placed on the same line or specified in separate REMOVALS lines).

For LIDs with Surface Layers: StorHt when confining walls or berms are present this is the maximum depth to which water can pond above the surface of the unit before overflow occurs (in inches or mm). For LIDs that experience overland flow it is the height of any surface depression storage. For swales, it is the height of its trapezoidal cross-section. VegFrac fraction of the surface storage volume that is filled with vegetation. Rough Manning's coefficient (n) for overland flow over surface soil cover, pavement, roof surface or a vegetative swale. Use 0 for other types of LIDs. Slope slope of a roof surface, pavement surface or vegetative swale (percent). Use 0 for other types of LIDs. Xslope slope (run over rise) of the side walls of a vegetative swale's cross-section. Use 0 for other types of LIDs. If either Rough or Slope values are 0 then any ponded water that exceeds the surface storage depth is assumed to completely overflow the LID control within a single time step.

For LIDs with Pavement Layers: Thick thickness of the pavement layer (inches or mm). Vratio void ratio (volume of void space relative to the volume of solids in the pavement for continuous systems or for the fill material used in modular systems). Note that porosity = void ratio / (1 + void ratio). FracImp ratio of impervious paver material to total area for modular systems; 0 for continuous porous pavement systems. Perm permeability of the concrete or asphalt used in continuous systems or hydraulic conductivity of the fill material (gravel or sand) used in modular systems (in/hr or mm/hr). Vclog the number of pavement layer void volumes of runoff treated it takes to completely clog the pavement. Use a value of 0 to ignore clogging. Treg the number of days that the pavement layer is allowed to clog before its permeability is restored, typically by vacuuming its surface. A value of 0 (the default) indicates that no permeability regeneration occurs. Freg The fractional degree to which the pavement's permeability is restored when a regeneration interval is reached. The default is 0 (no restoration) while a value of 1 indicates complete restoration to the original permeability value. Once regeneration occurs the pavement begins to clog once again at a rate determined by Vclog.

For LIDs with Soil Layers: Thick thickness of the soil layer (inches or mm). Por soil porosity (pore space volume / total volume). FC soil field capacity (moisture content of a fully drained soil). WP soil wilting point (moisture content of a fully dried soil). Ksat soil’s saturated hydraulic conductivity (in/hr or mm/hr). Kcoeff slope of the curve of log(conductivity) versus soil moisture deficit (porosity minus soil moisture) (dimensionless). Suct soil capillary suction (in or mm).

For LIDs with Storage Layers: Height thickness of the storage layer or height of a rain barrel (inches or mm). Vratio void ratio (volume of void space relative to the volume of solids in the layer). Note that porosity = void ratio / (1 + void ratio). Seepage the rate at which water seeps from the layer into the underlying native soil when first constructed (in/hr or mm/hr). If there is an impermeable floor or liner below the layer then use a value of 0. Vclog number of storage layer void volumes of runoff treated it takes to completely clog the layer. Use a value of 0 to ignore clogging. Covrd YES (the default) if a rain barrel is covered, NO if it is not. Values for Vratio, Seepage, and Vclog are ignored for rain barrels while Covrd applies only to rain barrels.

For LIDs with Drain Systems: Coeff coefficient C that determines the rate of flow through the drain as a function of height of stored water above the drain bottom. For Rooftop Disconnection it is the maximum flow rate (in inches/hour or mm/hour) that the roof’s gutters and downspouts can handle before overflowing. Expon exponent n that determines the rate of flow through the drain as a function of height of stored water above the drain outlet. Offset height of the drain line above the bottom of the storage layer or rain barrel (inches or mm). Delay number of dry weather hours that must elapse before the drain line in a rain barrel is opened (the line is assumed to be closed once rainfall begins). A value of 0 signifies that the barrel's drain line is always open and drains continuously. This parameter is ignored for other types of LIDs. Hopen The height of water (in inches or mm) in the drain's Storage Layer that causes the drain to automatically open. Use 0 to disable this feature. Hclose The height of water (in inches or mm) in the drain's Storage Layer that causes the drain to automatically close. Use 0 to disable this feature. Qcurve The name of an optional Control Curve that adjusts the computed drain flow as a function of the head of water above the drain. Leave blank if not applicable.

For Green Roof LIDs with Drainage Mats: Thick thickness of the drainage mat (inches or mm). Vratio ratio of void volume to total volume in the mat. Rough Manning's coefficient (n) used to compute the horizontal flow rate of drained water through the mat.

Remarks: The following table shows which layers are required (x) or are optional (o) for each type of LID process:

LID Type Surface Pavement Soil Storage Drain Drain Mat Bio-Retention Cell x x x o
Rain Garden x x
Green Roof x x x Infiltration Trench x x o
Permeable Pavement x x o x o
Rain Barrel x x
Rooftop Disconnection x x
Vegetative Swale x

The equation used to compute flow rate out of the underdrain per unit area of the LID (in in/hr or mm/hr) is where q is outflow, h is height of stored water (inches or mm) and Hd is the drain offset height. Note that the units of C depend on the unit system being used as well as the value assigned to n. The actual dimensions of an LID control are provided in the [LID_USAGE] section when it is placed in a particular subcatchment.

Examples: ;A street planter with no drain Planter BC Planter SURFACE 6 0.3 0 0 0 Planter SOIL 24 0.5 0.1 0.05 1.2 2.4 Planter STORAGE 12 0.5 0.5 0

;A green roof with impermeable bottom GR1 BC GR1 SURFACE 3 0 0 0 0 GR1 SOIL 3 0.5 0.1 0.05 1.2 2.4 GR1 STORAGE 3 0.5 0 0 GR1 DRAIN 5 0.5 0 0

;A rain barrel that drains 6 hours after rainfall ends RB12 RB RB12 STORAGE 36 0 0 0 RB12 DRAIN 10 0.5 0 6

;A grass swale 24 in. high with 5:1 side slope Swale VS Swale SURFACE 24 0 0.2 3 5

Section: [LID_USAGE]

Purpose: Deploys LID controls within specific subcatchment areas.

Format: Subcat LID Number Area Width InitSat FromImp ToPerv (RptFile DrainTo FromPerv)

Parameters: Subcat name of the subcatchment using the LID process. LID name of an LID process defined in the [LID_CONTROLS] section. Number number of replicate LID units deployed. Area area of each replicate unit (ft2 or m2). Width width of the outflow face of each identical LID unit (in ft or m). This parameter applies to roofs, pavement, trenches, and swales that use overland flow to convey surface runoff off of the unit. It can be set to 0 for other LID processes, such as bio-retention cells, rain gardens, and rain barrels that simply spill any excess captured runoff over their berms. InitSat the percent to which the LID's soil, storage, and drain mat zones are initially filled with water. For soil zones 0 % saturation corresponds to the wilting point moisture content while 100 % saturation has the moisture content equal to the porosity. FromImp the percent of the impervious portion of the subcatchment’s non-LID area whose runoff is treated by the LID practice. (E.g., if rain barrels are used to capture roof runoff and roofs represent 60% of the impervious area, then the impervious area treated is 60%). If the LID unit treats only direct rainfall, such as with a green roof, then this value should be 0. If the LID takes up the entire subcatchment then this field is ignored. ToPerv a value of 1 indicates that the surface and drain flow from the LID unit should be routed back onto the pervious area of the subcatchment that contains it. This would be a common choice to make for rain barrels, rooftop disconnection, and possibly green roofs. The default value is 0.

RptFile optional name of a file to which detailed time series results for the LID will be written. Enclose the name in double quotes if it contains spaces and include its full path if it resides in a different directory than the SWMM input file. Use ‘*’ if not applicable and an entry for DrainTo or FromPerv follows DrainTo optional name of subcatchment or node that receives flow from the unit’s drain line, if different from the outlet of the subcatchment that the LID is placed in. Use ‘*’ if not applicable and an entry for FromPerv follows. FromPerv optional percent of the pervious portion of the subcatchment’s non-LID area whose runoff is treated by the LID practice. The default value is 0.

Remarks: If ToPerv is set to 1 and DrainTo set to some other outlet, then only the excess surface flow from the LID unit will be routed back to the subcatchment’s pervious area while the underdrain flow will be sent to DrainTo. More than one type of LID process can be deployed within a subcatchment as long as their total area does not exceed that of the subcatchment and the total percent impervious area treated does not exceed 100.

Examples: ;34 rain barrels of 12 sq ft each are placed in ;subcatchment S1. They are initially empty and treat 17% ;of the runoff from the subcatchment’s impervious area. ;The outflow from the barrels is returned to the ;subcatchment’s pervious area. S1 RB14 34 12 0 0 17 1

;Subcatchment S2 consists entirely of a single vegetative ;swale 200 ft long by 50 ft wide. S2 Swale 1 10000 50 0 0 0 “swale.rpt”

Section: [AQUIFERS]

Purpose: Supplies parameters for each unconfined groundwater aquifer in the study area. Aquifers consist of two zones – a lower saturated zone and an upper unsaturated zone with a moving boundary between the two.

Format: Name Por WP FC Ks Kslp Tslp ETu ETs Seep Ebot Egw Umc (Epat)

Parameters: Name name assigned to aquifer. Por soil porosity (pore space volume / total volume). WP soil wilting point (moisture content of a fully dried soil). FC soil field capacity (moisture content of a fully drained soil). Ks saturated hydraulic conductivity (in/hr or mm/hr). Kslp slope of the logarithm of hydraulic conductivity versus moisture deficit (porosity minus moisture content) curve (dimensionless). Tslp slope of soil tension versus moisture content curve (inches or mm). ETu fraction of total evaporation available for evapotranspiration in the upper unsaturated zone. ETs maximum depth into the lower saturated zone over which evapotranspiration can occur (ft or m). Seep seepage rate from saturated zone to deep groundwater when water table is at ground surface (in/hr or mm/hr). Ebot elevation of the bottom of the aquifer (ft or m). Egw groundwater table elevation at start of simulation (ft or m). Umc unsaturated zone moisture content at start of simulation (volumetric fraction). Epat name of optional monthly time pattern used to adjust the upper zone evaporation fraction for different months of the year. Remarks: Local values for Ebot, Egw, and Umc can be assigned to specific subcatchments in the [GROUNDWATER] section.

Section: [GROUNDWATER]

Purpose: Supplies parameters that determine the rate of groundwater flow between the aquifer underneath a subcatchment and a node of the conveyance system.

Format: Subcat Aquifer Node Esurf A1 B1 A2 B2 A3 Dsw (Egwt Ebot Egw Umc)

Parameters: Subcat subcatchment name. Aquifer name of groundwater aquifer underneath the subcatchment. Node name of a node in the conveyance system exchanging groundwater with the aquifer. Esurf surface elevation of the subcatchment (ft or m). A1 groundwater flow coefficient (see below). B1 groundwater flow exponent (see below). A2 surface water flow coefficient (see below). B2 surface water flow exponent (see below). A3 surface water – groundwater interaction coefficient (see below). Dsw fixed depth of surface water at the receiving node (ft or m) (set to zero if surface water depth will vary as computed by flow routing). Egwt threshold groundwater table elevation which must be reached before any flow occurs (ft or m). Leave blank (or enter *) to use the elevation of the receiving node's invert. The following optional parameters can be used to override the values supplied for the subcatchment’s aquifer. Ebot elevation of the bottom of the aquifer (ft or m). Egw groundwater table elevation at the start of the simulation (ft or m). Umc unsaturated zone moisture content at start of simulation (volumetric fraction).

Remarks: The flow coefficients are used in the following equation that determines the lateral groundwater flow rate based on groundwater and surface water elevations: QL = A1 (Hgw – Hcb) B1 – A2 (Hsw – Hcb) B2 + A3 Hgw Hsw where: QL = lateral groundwater flow (cfs per acre or cms per hectare), Hgw = height of saturated zone above the bottom of the aquifer (ft or m), Hsw = height of surface water at the receiving node above the aquifer bottom (ft or m), Hcb = height of the channel bottom above the aquifer bottom (ft or m).

Section: [GWF]

Purpose: Defines custom groundwater flow equations for specific subcatchments.

Format: Subcat LATERAL/DEEP Expr

Parameters: Subcat subcatchment name. Expr a math formula expressing the rate of groundwater flow (in cfs per acre or cms per hectare for lateral flow or in/hr or mm/hr for deep flow) as a function of the following variables: Hgw (for height of the groundwater table) Hsw (for height of the surface water) Hcb (for height of the channel bottom) Hgs (for height of ground surface) where all heights are relative to the aquifer bottom and have units of either feet or meters; Ks (for saturated hydraulic conductivity in in/hr or mm/hr) K (for unsaturated hydraulic conductivity in in/hr or mm/hr) Theta (for moisture content of the unsaturated zone) Phi (for aquifer soil porosity) Fi (for infiltration rate from the ground surface in in/hr or mm/hr) Fu (for percolation rate from the upper unsaturated zone in in/hr or mm/hr) A (for subcatchment area in acres or hectares)

Remarks: Use LATERAL to designate an expression for lateral groundwater flow (to a node of the conveyance network) and DEEP for vertical loss to deep groundwater. See the [TREATMENT] section for a list of built-in math functions that can be used in Expr. In particular, the STEP(x) function is 1 when x > 0 and is 0 otherwise.

Examples: ;Two-stage linear reservoir for lateral flow Subcatch1 LATERAL 0.001*Hgw + 0.05*(Hgw–5)*STEP(Hgw–5)

;Constant seepage rate to deep aquifer Subactch1 DEEP 0.002

Section: [SNOWPACKS]

Purpose: Specifies parameters that govern how snowfall accumulates and melts on the plowable, impervious and pervious surfaces of subcatchments.

Formats: Name PLOWABLE Cmin Cmax Tbase FWF SD0 FW0 SNN0 Name IMPERVIOUS Cmin Cmax Tbase FWF SD0 FW0 SD100
Name PERVIOUS Cmin Cmax Tbase FWF SD0 FW0 SD100 Name REMOVAL Dplow Fout Fimp Fperv Fimelt (Fsub Scatch)

Parameters: Name name assigned to snowpack parameter set . Cmin minimum melt coefficient (in/hr-deg F or mm/hr-deg C). Cmax maximum melt coefficient (in/hr-deg F or mm/hr-deg C). Tbase snow melt base temperature (deg F or deg C). FWF ratio of free water holding capacity to snow depth (fraction). SD0 initial snow depth (in or mm water equivalent). FW0 initial free water in pack (in or mm). SNN0 fraction of impervious area that can be plowed. SD100 snow depth above which there is 100% cover (in or mm water equivalent). Dplow depth of snow on plowable areas at which snow removal begins (in or mm). Fout fraction of snow on plowable area transferred out of watershed. Fimp fraction of snow on plowable area transferred to impervious area by plowing. Fperv fraction of snow on plowable area transferred to pervious area by plowing. Fimelt fraction of snow on plowable area converted into immediate melt. Fsub fraction of snow on plowable area transferred to pervious area in another subcatchment. Scatch name of subcatchment receiving the Fsub fraction of transferred snow.

Remarks: Use one set of PLOWABLE, IMPERVIOUS, and PERVIOUS lines for each snow pack parameter set created. Snow pack parameter sets are assigned to specific subcatchments in the [SUBCATCHMENTS] section. Multiple subcatchments can share the same set of snow pack parameters. The PLOWABLE line contains parameters for the impervious area of a subcatchment that is subject to snow removal by plowing but not to areal depletion. This area is the fraction SNN0 of the total impervious area. The IMPERVIOUS line contains parameter values for the remaining impervious area and the PERVIOUS line does the same for the entire pervious area. Both of the latter two areas are subject to areal depletion. The REMOVAL line describes how snow removed from the plowable area is transferred onto other areas. The various transfer fractions should sum to no more than 1.0. If the line is omitted then no snow removal takes place.

UEB site and model override

An additional row supplies the UEB site parameters of a named pack:

Name UEB Fc F Qg Aep (U0) (MODEL UEB / DEGREE_DAY)

Fc is forest-cover fraction (0 to 1); F is the nonnegative precipitation drift multiplier; Qg is ground heat flux (W/m²); Aep is positive extinction depth (m); and optional U0 is initial snow energy (kJ/m², default 0). These units are fixed in both US and SI projects. All values must be finite. An authored UEB row selects UEB for that pack unless MODEL DEGREE_DAY is appended. A pack without this row follows the shared SNOWMELT_MODEL in [TEMPERATURE].

The PLOWABLE, IMPERVIOUS and PERVIOUS rows still supply initial snow and free water. Their SD0 and SD100 columns are water-equivalent depths, distinct from geometric snow thickness. Mesh assignments in [2D_SNOW_DEFAULTS] and [2D_SNOW] reference these same named packs but maintain independent state per cell; mesh initialization uses the pack's PERVIOUS row. Mesh FC, F, QG and AEP overrides do not edit the named pack.

Section: [JUNCTIONS]

Purpose: Identifies each junction node of the drainage system. Junctions are points in space where channels and pipes connect together. For sewer systems they can be either connection fittings or manholes.

Format: Name Elev (Ymax Y0 Ysur Apond StorageArea)

Parameters: Name name assigned to junction node. Elev elevation of the junction’s invert (ft or m). Ymax depth from ground to invert elevation (ft or m) (default is 0). Y0 water depth at the start of the simulation (ft or m) (default is 0). Ysur maximum additional pressure head above the ground elevation that the junction can sustain under surcharge conditions (ft or m) (default is 0). Apond area subjected to surface ponding once water depth exceeds Ymax + Ysur (ft2 or m2) (default is 0). StorageArea physical constant-area junction chamber (ft2 or m2), optional seventh token; default 0 retains legacy behavior.

Remarks: Positive StorageArea is supported by updated OpenSWMM 5.3.0 dynamic wave and qualified 6.0.0 dynamic-wave/finite-volume paths. It preserves the node's JUNCTION identity. Below the rim, physical volume is StorageArea times depth, including surcharge above pipe crowns. Shaft volume is capped at the rim; ponding adds separate above-rim volume using Apond. Ysur is pressure allowance and does not extend physical shaft volume. Omission or zero preserves prior behavior. Kinematic/steady routing rejects a positive area rather than ignoring it. Physical chamber continuity uses a tighter internal head tolerance. If a small chamber cannot resolve its water budget within the configured routing step and trial limit, the run stops; reduce ROUTING_STEP or increase MAX_TRIALS instead of increasing the physical area to stabilize the calculation.

Physical junctions in finite-volume routing require the CPU backend and zero SurDepth; explicit ponding and rim flooding are supported. Above-rim pressure allowance requires dynamic wave. A selected device plugin refuses physical junctions until its closure is qualified. Positive chamber areas are not yet qualified with DYNAMIC_SLOT; select EXTRAN or SLOT instead.

MIN_SURFAREA remains the numerical stability area, not the physical chamber area. Explicit physical areas are not enlarged to that global value. Virtual/inlet junctions, storage nodes, outfalls and dividers do not accept this ordinary-junction parameter. Stock EPA export refuses positive StorageArea because older parsers can silently ignore the additional token. Use the OpenSWMM 5.3.0 compatibility profile instead.

Example (US units):

[JUNCTIONS]
;;Name Elev MaxDepth InitDepth SurDepth Aponded StorageArea
MH1    100  10       0         0        0       12.566

If Ymax is 0 then SWMM sets the junction’s maximum depth to the distance from its invert to the top of the highest connecting link. If the junction is part of a force main section of the system then set Ysur to the maximum pressure that the system can sustain. Surface ponding can only occur when Apond is non-zero and the ALLOW_PONDING analysis option is turned on.

Section: [OUTFALLS]

Purpose: Identifies each outfall node (i.e., final downstream boundary) of the drainage system and the corresponding water stage elevation. Only one link can be incident on an outfall node.

Formats: Name Elev FREE (Gated) (RouteTo) Name Elev NORMAL (Gated) (RouteTo) Name Elev FIXED Stage (Gated) (RouteTo) Name Elev TIDAL Tcurve (Gated) (RouteTo) Name Elev TIMESERIES Tseries (Gated) (RouteTo)

Parameters: Name name assigned to outfall node. Elev node’s invert elevation (ft or m). Stage elevation of a fixed stage outfall (ft or m). Tcurve name of a curve in the [CURVES] section containing tidal height (i.e., outfall stage) versus hour of day over a complete tidal cycle. Tseries name of a time series in [TIMESERIES] section that describes how outfall stage varies with time. Gated YES or NO depending on whether a flap gate is present that prevents reverse flow. The default is NO. RouteTo optional name of a subcatchment that receives the outfall's discharge. The default is not to route the outfall’s discharge.

Section: [DIVIDERS]

Purpose: Identifies each flow divider node of the drainage system. Flow dividers are junctions with exactly two outflow conduits where the total outflow is divided between the two in a prescribed manner.

Formats: Name Elev DivLink OVERFLOW (Ymax Y0 Ysur Apond) Name Elev DivLink CUTOFF Qmin (Ymax Y0 Ysur Apond) Name Elev DivLink TABULAR Dcurve (Ymax Y0 Ysur Apond) Name Elev DivLink WEIR Qmin Ht Cd (Ymax Y0 Ysur Apond)

Parameters: Name name assigned to divider node. Elev node’s invert elevation (ft or m). DivLink name of the link to which flow is diverted. Qmin flow at which diversion begins for either a CUTOFF or WEIR divider (flow units). Dcurve name of a curve for a TABULAR divider that relates diverted flow to total flow. Ht height of a WEIR divider (ft or m). Cd discharge coefficient for a WEIR divider. Ymax depth from the ground to the node’s invert elevation (ft or m) (default is 0). Y0 water depth at the start of the simulation (ft or m) (default is 0). Ysur maximum additional pressure head above the ground elevation that the node can sustain under surcharge conditions (ft or m) (default is 0). Apond area subjected to surface ponding once water depth exceeds Ymax + Ysur (ft2 or m2) (default is 0).

Remarks: If Ymax is 0 then SWMM sets the node’s maximum depth equal to the distance from its invert to the top of the highest connecting link. Surface ponding can only occur when Apond is non-zero and the ALLOW_PONDING analysis option is turned on. Divider nodes are only active under the Steady Flow or Kinematic Wave analysis options. For Dynamic Wave flow routing they behave the same as Junction nodes.

Section: [STORAGE]

Purpose: Identifies each storage node of the drainage system. Storage nodes can have any shape as specified by a surface area versus water depth relation.

Formats:
Name Elev Ymax Y0 TABULAR Acurve (Ysur Fevap Psi Ksat IMD) Name Elev Ymax Y0 FUNCTIONAL A1 A2 A0 (Ysur Fevap Psi Ksat IMD) Name Elev Ymax Y0 Shape L W Z (Ysur Fevap Psi Ksat IMD)

Parameters: Name name assigned to storage node. Elev node’s invert elevation (ft or m). Ymax water depth when the storage node is full (ft or m). Y0 water depth at the start of the simulation (ft or m). Acurve name of a curve in the [CURVES] section that relates surface area (ft2 or m2) to depth (ft or m) for TABULAR geometry. A1 coefficient of a FUNCTIONAL relation between surface area and depth. A2 exponent of a FUNCTIONAL relation between surface area and depth. A0 constant of a FUNCTIONAL relation between surface area and depth. Shape shape used to relate surface area to depth; choices are CYLINDRICAL, CONICAL, PARABOLOID, or PYRAMIDAL. Ysur maximum additional pressure head above full depth that a closed storage unit can sustain under surcharge conditions (ft or m) (default is 0). L, W, Z dimensions of the storage unit's shape (see table below).
Fevap fraction of potential evaporation from the storage unit’s water surface realized (default is 0). Optional seepage parameters for soil surrounding the storage unit: Psi suction head (inches or mm). Ksat saturated hydraulic conductivity (in/hr or mm/hr). IMD initial moisture deficit (porosity minus moisture content) (fraction). Remarks: A1, A2, and A0 are used in the following expression that relates surface area (ft2 or m2) to water depth (ft or m) for a storage unit with FUNCTIONAL geometry: Area=A0+A1〖Depth〗^A2 For TABULAR geometry, the surface area curve will be extrapolated outwards to meet the unit's maximum depth if need be. The dimensions of storage units with other shapes are defined as follows: Shape L W Z CYLINDRICAL major axis length minor axis width not used CONICAL major axis length of base minor axis width of base side slope (run/rise) PARABOLOID major axis length at full height minor axis width at full height full height PYRAMIDAL base length base width side slope (run/rise)

The parameters Psi, Ksat, and IMD need only be supplied if seepage loss through the soil at the bottom and sloped sides of the storage unit should be considered. They are the same Green-Ampt infiltration parameters described in the [INFILTRATION] section. If Ksat is zero then no seepage occurs while if IMD is zero then seepage occurs at a constant rate equal to Ksat. Otherwise seepage rate will vary with storage depth.

Section: [CONDUITS]

Purpose: Identifies each conduit link of the drainage system. Conduits are pipes or channels that convey water from one node to another.

Format: Name Node1 Node2 Length N Z1 Z2 (Q0 Qmax)

Parameters: Name name assigned to conduit link. Node1 name of the conduit’s upstream node. Node2 name of the conduit’s downstream node. Length conduit length (ft or m). N Manning’s roughness coefficient (n). Z1 offset of the conduit’s upstream end above the invert of its upstream node (ft or m). Z2 offset of the conduit’s downstream end above the invert of its downstream node (ft or m). Q0 flow in the conduit at the start of the simulation (flow units) (default is 0). Qmax maximum flow allowed in the conduit (flow units) (default is no limit).

Remarks: The figure below illustrates the meaning of the Z1 and Z2 parameters.

These offsets are expressed as a relative distance above the node invert if the LINK_OFFSETS option is set to DEPTH (the default) or as an absolute elevation if it is set to ELEVATION.

Section: [PUMPS]

Purpose: Identifies each pump link of the drainage system.

Format: Name Node1 Node2 Pcurve (Status Startup Shutoff)

Parameters: Name name assigned to pump link. Node1 name of the pump’s inlet node. Node2 name of the pump’s outlet node. Pcurve name of a pump curve listed in the [CURVES] section of the input. Status pump’s status at the start of the simulation (either ON or OFF; default is ON). Startup depth at the inlet node when the pump turns on (ft or m) (default is 0). Shutoff depth at inlet node when the pump shuts off (ft or m) (default is 0).

Remarks: See CHAPTER 1 - The Conceptual Model for a description of the different types of pumps available.

Section: [ORIFICES]

Purpose: Identifies each orifice link of the drainage system. An orifice link serves to limit the flow exiting a node and is often used to model flow diversions and storage node outlets.

Format: Name Node1 Node2 Type Offset Cd (Gated Orate)

Parameters: Name name assigned to orifice link. Node1 name of the orifice’s inlet node. Node2 name of the orifice’s outlet node. Type the type of orifice - either SIDE if oriented in a vertical plane or BOTTOM if oriented in a horizontal plane. Offset amount that a Side Orifice’s bottom or the position of a Bottom Orifice is offset above the invert of inlet node (ft or m, expressed as either a depth or as an elevation, depending on the LINK_OFFSETS option setting). Cd discharge coefficient (unitless). Flap YES if a flap gate prevents reverse flow, NO if not (default is NO). Orate time in decimal hours to open a fully closed orifice (or close a fully open one). Use 0 if the orifice can open/close instantaneously.

Remarks: The geometry of an orifice’s opening must be described in the [XSECTIONS] section. The only allowable shapes are CIRCULAR and RECT_CLOSED (closed rectangular).

Section: [WEIRS]

Purpose: Identifies each weir link of the drainage system. Weirs are used to model flow diversions and storage node outlets.

Format:
Name Node1 Node2 Type CrstHt Cd (Gated EC Cd2 Sur (Width Surf))

Parameters: Name name assigned to weir link. Node1 name of the weir’s inlet node. Node2 name of the weir’s outlet node. Type TRANSVERSE, SIDEFLOW, V-NOTCH, TRAPEZOIDAL or ROADWAY. CrstHt amount that the weir’s opening is offset above the invert of inlet node (ft or m, expressed as either a depth or as an elevation, depending on the LINK_OFFSETS option setting). Cd weir discharge coefficient (for CFS if using US flow units or CMS if using metric flow units). Gated YES if a flap gate prevents reverse flow, NO if not (default is NO). EC number of end contractions for a TRANSVERSE or TRAPEZOIDAL weir (default is 0). Cd2 discharge coefficient for the triangular ends of a TRAPEZOIDAL weir (for CFS if using US flow units or CMS if using metric flow units) (default is the value of Cd). Sur YES if the weir can surcharge (have an upstream water level higher than the height of the weir’s opening); NO if it cannot (default is YES). The following parameters apply only to ROADWAY weirs: Width width of road lanes and shoulders for a ROADWAY weir (ft or m). Surf type of road surface for a ROADWAY weir: PAVED or GRAVEL.

Remarks: The geometry of a weir’s opening is described in the [XSECTIONS] section. The following shapes must be used with each type of weir:

Weir Type Cross-Section Shape Transverse RECT_OPEN Sideflow RECT_OPEN V-Notch TRIANGULAR Trapezoidal TRAPEZOIDAL Roadway RECT_OPEN

The ROADWAY weir is a broad crested rectangular weir used model roadway crossings usually in conjunction with culvert-type conduits. It uses the FHWA HDS-5 method to determine a discharge coefficient as a function of flow depth and roadway width and surface. If no roadway data are provided then the weir behaves as a TRANSVERSE weir with Cd as its discharge coefficient. Note that if roadway data are provided, then values for the other optional weir parameters (NO for Gated, 0 for EC, 0 for Cd2, and NO for Sur) must be entered even though they do not apply to ROADWAY weirs.

Section: [OUTLETS]

Purpose: Identifies each outlet flow control device of the drainage system. These are devices used to model outflows from storage units or flow diversions that have a user-defined relation between flow rate and water depth.

Formats: Name Node1 Node2 Offset TABULAR/DEPTH Qcurve (Gated) Name Node1 Node2 Offset TABULAR/HEAD Qcurve (Gated) Name Node1 Node2 Offset FUNCTIONAL/DEPTH C1 C2 (Gated) Name Node1 Node2 Offset FUNCTIONAL/HEAD C1 C2 (Gated)

Parameters: Name name assigned to outlet link. Node1 name of the outlet’s inlet node. Node2 name of the outlet’s outlet node. Offset amount that the outlet is offset above the invert of its inlet node (ft or m, expressed as either a depth or as an elevation, depending on the LINK_OFFSETS option setting). Qcurve name of the rating curve listed in the [CURVES] section that describes outflow rate (flow units) as a function of: water depth above the offset elevation at the inlet node (ft or m) for a TABULAR/DEPTH outlet head difference (ft or m) between the inlet and outflow nodes for a TABULAR/HEAD outlet. C1, C2 coefficient and exponent, respectively, of a power function that relates outflow (Q) to: water depth (ft or m) above the offset elevation at the inlet node for a FUNCTIONAL/DEPTH outlet head difference (ft or m) between the inlet and outflow nodes for a FUNCTIONAL/HEAD outlet. (i.e., Q=C1H^C2 where H is either depth or head). Gated YES if a flap gate prevents reverse flow, NO if not (default is NO).

Section: [XSECTIONS]

Purpose: Provides cross-section geometric data for conduit and regulator links of the drainage system.

Formats: Link Shape Geom1 Geom2 Geom3 Geom4 (Barrels Culvert) Link IRREGULAR Tsect Link STREET Street

Parameters: Link name of a conduit, orifice, or weir. Shape a cross-section shape (see Tables D-1 below or 3-1 for available shapes). Geom1 full height of the cross-section (ft or m). Geom2-4 auxiliary parameters (width, side slopes, etc.) as listed in Table D-1. Barrels number of barrels (i.e., number of parallel pipes of equal size, slope, and roughness) associated with a conduit (default is 1). Culvert code number from Table A.10 for the conduit’s inlet geometry if it is a culvert subject to possible inlet flow control (leave blank otherwise). Curve name of a Shape Curve in the [CURVES] section that defines how cross-section width varies with depth. Tsect name of an entry in the [TRANSECTS] section that describes the cross-section geometry of an irregular channel. Street name of an entry in the [STREETS] section that describes the cross-section geometry of a street.

Remarks: The standard conduit shapes and their geometric parameters are listed in the following table:

Table D 2 Geometric parameters of conduit cross sections Shape Geom1 Geom2 Geom3 Geom4 CIRCULAR Diameter
FORCE_MAIN Diameter Roughness1
FILLED_CIRCULAR2 Diameter Sediment Depth
RECT_CLOSED Full Height Top Width
RECT_OPEN Full Height Top Width
TRAPEZOIDAL Full Height Base Width Left Slope3 Right Slope3 TRIANGULAR Full Height Top Width
HORIZ_ELLIPSE Full Height Max. Width Size Code4
VERT_ELLIPSE Full Height Max. Width Size Code4
ARCH Full Height Max. Width Size Code5
PARABOLIC Full Height Top Width
POWER Full Height Top Width Exponent
RECT_TRIANGULAR Full Height Top Width Triangle Height
RECT_ROUND Full Height Top Width Bottom Radius
MODBASKETHANDLE Full Height Base Width Top Radius6
EGG Full Height
HORSESHOE Full Height
GOTHIC Full Height
CATENARY Full Height
SEMIELLIPTICAL Full Height
BASKETHANDLE Full Height
SEMICIRCULAR Full Height
CUSTOM Full Height Shape Curve
1C-factors are used when H-W is the FORCE_MAIN_EQUATION choice in the [OPTIONS] section while roughness heights (in inches or mm) are used for D-W. 2A circular conduit partially filled with sediment to a specified depth. 3Slopes are horizontal run / vertical rise. 4Size code of a standard shaped elliptical pipe as listed in Appendix A12. Leave blank (or 0) if the pipe has custom dimensions. 5Size code of a standard arch pipe as listed in Appendix A13. Leave blank (or 0) if the pipe has custom dimensions). 6Set to zero to use a standard modified baskethandle shape whose top radius is half the base width. The CUSTOM shape is a closed conduit whose width versus height is described by a user-supplied Shape Curve. An IRREGULAR cross-section is used to model an open channel whose geometry is described by a Transect object. A STREET cross-section is used to model street conduits and inlet flow capture (see the [INLETS] and [INLETS_USAGE] sections). The Culvert code number is used only for closed conduits acting as culverts that should be analyzed for inlet control conditions using the FHWA HDS-5 methodology.

Section: [TRANSECTS]

Purpose: Describes the cross-section geometry of natural channels or conduits with irregular shapes following the HEC-2 data format.

Formats: NC Nleft Nright Nchanl X1 Name Nsta Xleft Xright 0 0 0 Lfactor Wfactor Eoffset GR Elev Station ... Elev Station

Parameters: Nleft Manning’s roughness coefficient (n) of right overbank portion of channel (use 0 if no change from previous NC line). Nright Manning’s roughness coefficient (n) of right overbank portion of channel (use 0 if no change from previous NC line. Nchanl Manning’s roughness coefficient (n) of main channel portion of channel (use 0 if no change from previous NC line. Name name assigned to the transect. Nsta number of stations across the cross-section’s width at which elevation data is supplied. Xleft station position which ends the left overbank portion of the channel (ft or m). Xright station position which begins the right overbank portion of the channel (ft or m). Lfactor meander modifier that represents the ratio of the length of a meandering main channel to the length of the overbank area that surrounds it (use 0 if not applicable). Wfactor factor by which distances between stations should be multiplied to increase (or decrease) the width of the channel (enter 0 if not applicable). Eoffset amount to be added (or subtracted) from the elevation of each station (ft or m). Elev elevation of the channel bottom at a cross-section station relative to some fixed reference (ft or m). Station distance of a cross-section station from some fixed reference (ft or m).

Remarks: Transect geometry is described as shown below, assuming that one is looking in a downstream direction:

The first line in this section must always be a NC line. After that, the NC line is only needed when a transect has different Manning’s n values than the previous one. The Manning’s n values on the NC line will supersede any roughness value entered for the conduit which uses the irregular cross-section. There should be one X1 line for each transect. Any number of GR lines may follow, and each GR line can have any number of Elevation-Station data pairs. (In HEC-2 the GR line is limited to 5 stations.) The station that defines the left overbank boundary on the X1 line must correspond to one of the station entries on the GR lines that follow. The same holds true for the right overbank boundary. If there is no match, a warning will be issued and the program will assume that no overbank area exists. The meander modifier is applied to all conduits that use this particular transect for their cross section. It assumes that the length supplied for these conduits is that of the longer main channel. SWMM will use the shorter overbank length in its calculations while increasing the main channel roughness to account for its longer length.

Section: [STREETS]

Purpose: Describes the cross-section geometry of conduits that represent streets.

Format: Name Tcrown Hcurb Sx nRoad (a W)(Sides Tback Sback nBack)

Parameters: Name name assigned to the street cross-section Tcrown distance from street’s curb to its crown (ft or m) Hcurb curb height (ft or m) Sx street cross slope (%) nRoad Manning’s roughness coefficient (n) of the road surface a gutter depression height (in or mm) (default = 0) W depressed gutter width (ft or m) (default = 0) Sides 1 for single sided street or 2 for two-sided street (default = 2) Tback street backing width (ft or m) (default = 0) Sback street backing slope (%) (default = 0) nBack street backing Manning’s roughness coefficient (n) (default = 0)

Remarks:

If the street has no depressed gutter (a = 0) then the gutter width entry is ignored. If the street has no backing then the three backing parameters can be omitted.

Section: [INLETS]

Purpose: Defines inlet structure designs used to capture street and channel flow that are sent to below ground sewers.

Format: Name GRATE/DROP_GRATE Length Width Type (Aopen Vsplash) Name CURB/DROP_CURB Length Height (Throat) Name SLOTTED Length Width Name CUSTOM Dcurve/Rcurve

Parameters: Name name assigned to the inlet structure. Length length of the inlet parallel to the street curb (ft or m). Width width of a GRATE or SLOTTED inlet (ft or m). Height height of a CURB opening inlet (ft or m). Type type of GRATE used (see below). Aopen fraction of a GENERIC grate’s area that is open. Vsplash splash over velocity for a GENERIC grate (ft/s or m/s). Throat the throat angle of a CURB opening inlet (HORIZONTAL, INCLINED or VERTICAL). Dcurve name of a Diversion-type curve (captured flow v. approach flow) for a CUSTOM inlet. Rcurve name of a Rating-type curve (captured flow v. water depth) for a CUSTOM inlet.

Remarks: See CHAPTER 1 - The Conceptual Model for a description of the different types of inlets that SWMM can model. Use one line for each inlet design except for a combination inlet where one GRATE line describes its grated inlet and a second CURB line (with the same inlet name) describes its curb opening inlet.

GRATE, CURB, and SLOTTED inlets are used with STREET conduits, DROP_GRATE and DROP_CURB inlets with open channels, and a CUSTOM inlet with any conduit. GRATE and DROP_GRATE types can be any of the following: Grate Type Sketch Description P_BAR-50 Parallel bar grate with bar spacing 1⅞” on center P_BAR-50X100 Parallel bar grate with bar spacing 1⅞” on center and ⅜” diameter lateral rods spaced at 4” on center P_BAR-30 Parallel bar grate with 1⅛” on center bar spacing CURVED_VANE Curved vane grate with 3¼” longitudinal bar and 4¼” transverse bar spacing on center TILT_BAR-45 45 degree tilt bar grate with 2¼” longitudinal bar and 4” transverse bar spacing on center TILT_BAR-30 30 degree tilt bar grate with 3¼” and 4” on center longitudinal and lateral bar spacing respectively RETICULINE "Honeycomb" pattern of lateral bars and longitudinal bearing bars GENERIC A generic grate design.

Only a GENERIC type grate requires that Aopen and Vsplash values be provided. The other standard grate types have predetermined values of these parameters. (Splash over velocity is the minimum velocity that will cause some water to shoot over the inlet thus reducing its capture efficiency). A CUSTOM inlet takes the name of either a Diversion curve or a Rating curve as its only parameter (see the [CURVES] section). Diversion curves are best suited for on-grade inlets and Rating curves for on-sag inlets.

Examples: ; A 2-ft x 2-ft parallel bar grate InletType1 GRATE 2 2 P-BAR-30 ; A combination inlet InletType2 GRATE 2 2 CURVED_VANE InletType2 CURB 4 0.5 HORIZONTAL ; A custom inlet using Curve1 as its capture curve InletType3 CUSTOM Curve1

Section: [INLET_USAGE]

Purpose: Assigns inlet structures to specific street and open channel conduits.

Format: Conduit Inlet Node (Number Clogged Qmax aLocal wLocal Placement)

Parameters: Conduit name of a street or open channel conduit containing the inlet. Inlet name of an inlet structure (from the [INLETS] section) to use. Node name of the sewer node receiving flow captured by the inlet. Number number of replicate inlets placed on each side of the street. Clogged degree to which inlet capacity is reduced due to clogging (%). Qmax maximum flow that the inlet can capture (flow units). aLocal height of local gutter depression (in or mm). wLocal width of local gutter depression (ft or m). Placement AUTOMATIC, ON_GRADE, or ON_SAG.

Remarks: Only conduits with a STREET cross section can be assigned a curb and gutter inlet while drop inlets can only be assigned to conduits with a RECT_OPEN or TRAPEZOIDAL cross section. Only the first three parameters are required. The default number of inlets is 1 (for each side of a two-sided street) while the remaining parameters have default values of 0. A Qmax value of 0 indicates that the inlet has no flow restriction. The local gutter depression applies only over the length of the inlet unlike the continuous depression for a STREET cross section which exists over the full curb length. The default inlet placement is AUTOMATIC, meaning that the program uses the network topography to determine whether an inlet operates on-grade or on-sag. On-grade means the inlet is located on a continuous grade. On-sag means the inlet is located at a sag or sump point where all adjacent conduits slope towards the inlet leaving no place for water to flow except into the inlet.

Section: [LOSSES]

Purpose: Specifies minor head loss coefficients, flap gates, and seepage rates for conduits.

Format: Conduit Kentry Kexit Kavg (Flap Seepage)

Parameters: Conduit name of a conduit. Kentry minor head loss coefficient at the conduit’s entrance. Kexit minor head loss coefficient at the conduit’s exit. Kavg average minor head loss coefficient across the length of the conduit. Flap YES if the conduit has a flap valve that prevents back flow, NO otherwise. (Default is NO). Seepage Rate of seepage loss into the surrounding soil (in/hr or mm/hr). (Default is 0.)

Remarks: Minor losses are only computed for the Dynamic Wave flow routing option (see the [OPTIONS] section). They are computed as Kv2/2g where K = minor loss coefficient, v = velocity, and g = acceleration of gravity. Entrance losses are based on the velocity at the entrance of the conduit, exit losses on the exit velocity, and average losses on the average velocity. Only enter data for conduits that actually have minor losses, flap valves, or seepage losses.

Section: [CONTROLS]

Purpose: Determines how pumps and regulators will be adjusted based on simulation time or conditions at specific nodes and links.

Formats: Each control rule is a series of statements of the form: RULE ruleID IF condition_1 AND condition_2 OR condition_3 AND condition_4 Etc. THEN action_1 AND action_2 Etc. ELSE action_3 AND action_4 Etc. PRIORITY value

Parameters: ruleID an ID label assigned to the rule. condition_n a condition clause. action_n an action clause. value a priority value (e.g., a number from 1 to 5).

Remarks: Please refer to Section C.3 for a complete description of the control rule format plus examples of different types of rule statements.

Section: [POLLUTANTS]

Purpose: Identifies the pollutants being analyzed.

Format: Name Units Crain Cgw Cii Kd (Sflag CoPoll CoFract Cdwf Cinit)

Parameters: Name name assigned to a pollutant. Units concentration units (MG/L for milligrams per liter, UG/L for micrograms per liter, or #/L for direct count per liter). Crain concentration of the pollutant in rainfall (concentration units). Cgw concentration of the pollutant in groundwater (concentration units). Cii concentration of the pollutant in rainfall-dependent infiltration and inflow (concentration units). Kdecay first-order decay coefficient (1/days). Sflag YES if pollutant buildup occurs only when there is snow cover, NO otherwise (default is NO). CoPoll name of a co-pollutant (default is no co-pollutant designated by a *). CoFract fraction of the co-pollutant’s concentration (default is 0). Cdwf pollutant concentration in dry weather flow (default is 0). Cinit pollutant concentration throughout the conveyance system at the start of the simulation (default is 0). Remarks: FLOW is a reserved word and cannot be used to name a pollutant. Parameters Sflag through Cinit can be omitted if they assume their default values. If there is no co-pollutant but non-default values for Cdwf or Cinit, then enter an asterisk (*) for the co-pollutant name. When pollutant X has a co-pollutant Y, it means that fraction CoFract of pollutant Y’s runoff concentration is added to pollutant X’s runoff concentration when wash off from a subcatchment is computed. The dry weather flow concentration can be overridden for any specific node of the conveyance system by editing the node’s Inflows property (see the [INFLOWS] section).

Section: [LANDUSES]

Purpose: Identifies the various categories of land uses within the drainage area. Each subcatchment area can be assigned a different mix of land uses. Each land use can be subjected to a different street sweeping schedule. Land uses are only used in conjunction with pollutant buildup and wash off.

Format: Name (SweepInterval Availability LastSweep)

Parameters: Name land use name. SweepInterval days between street sweeping. Availability fraction of pollutant buildup available for removal by street sweeping. LastSweep days since last sweeping at the start of the simulation.

Section: [COVERAGES]

Purpose: Specifies the percentage of a subcatchment’s area that is covered by each category of land use.

Format: Subcat Landuse Percent Landuse Percent . . .

Parameters: Subcat subcatchment name. Landuse land use name. Percent percent of the subcatchment’s area covered by the land use.

Remarks: More than one pair of land use - percentage values can be entered per line. If more than one line is needed, then the subcatchment name must still be entered first on the succeeding lines. If a land use does not pertain to a subcatchment, then it does not have to be entered. If no land uses are associated with a subcatchment then no pollutants will appear in the runoff from the subcatchment.

Section: [LOADINGS]

Purpose: Specifies the pollutant buildup that exists on each subcatchment at the start of a simulation.

Format: Subcat Pollut InitBuildup Pollut InitBuildup ...

Parameters: Subcat name of a subcatchment. Pollut name of a pollutant. InitBuildup initial buildup of the pollutant (lbs/acre or kg/hectare).

Remarks: More than one pair of pollutant - buildup values can be entered per line. If more than one line is needed, then the subcatchment name must still be entered first on the succeeding lines. If an initial buildup is not specified for a pollutant, then its initial buildup is computed by applying the DRY_DAYS option (specified in the [OPTIONS] section) to the pollutant’s buildup function for each land use in the subcatchment.

Section: [BUILDUP]

Purpose: Specifies the rate at which pollutants build up over different land uses between rain events.

Format: Landuse Pollutant FuncType C1 C2 C3 PerUnit

Parameters: Landuse land use name. Pollutant pollutant name. FuncType buildup function type: ( POW / EXP / SAT / EXT ). C1,C2,C3 buildup function parameters (see Table D-2). PerUnit AREA if buildup is per unit area, CURBLENGTH if per length of curb.

Remarks: Buildup is measured in pounds (kilograms) per unit of area (or curb length) for pollutants whose concentration units are either mg/L or ug/L. If the concentration units are counts/L, then buildup is expressed as counts per unit of area (or curb length).

Table D 3 Pollutant buildup functions Name Function Equation* POW Power Min (C1, C2*tC3) EXP Exponential C1*(1 – exp(-C2*t)) SAT Saturation C1*t / (C3 + t) EXT External See below *t is antecedent dry days.

For the EXT buildup function, C1 is the maximum possible buildup (mass per area or curb length), C2 is a scaling factor, and C3 is the name of a Time Series that contains buildup rates (as mass per area or curb length per day) as a function of time.

Section: [WASHOFF]

Purpose: Specifies the rate at which pollutants are washed off from different land uses during rain events.

Format: Landuse Pollutant FuncType C1 C2 SweepRmvl BmpRmvl

Parameters: Landuse land use name. Pollutant pollutant name. FuncType washoff function type: EXP / RC / EMC. C1, C2 washoff function coefficients(see Table D-3). SweepRmvl street sweeping removal efficiency (percent).
BmpRmvl BMP removal efficiency (percent).

Remarks: Table D 4 Pollutant wash off functions Name Function Equation Units EXP Exponential C1 (runoff)C2 (buildup) Mass/hour RC Rating Curve C1 (runoff)C2 Mass/sec EMC Event Mean Concentration C1 Mass/Liter

Each washoff function expresses its results in different units. For the Exponential function the runoff variable is expressed in catchment depth per unit of time (inches per hour or millimeters per hour), while for the Rating Curve function it is in whatever flow units were specified in the [OPTIONS] section of the input file (e.g., CFS, CMS, etc.).

The buildup parameter in the Exponential function is the current total buildup over the subcatchment’s land use area in mass units. The units of C1 in the Exponential function are (in/hr) -C2 per hour (or (mm/hr) -C2 per hour). For the Rating Curve function, the units of C1 depend on the flow units employed. For the EMC (event mean concentration) function, C1 is always in concentration units.

Section: [TREATMENT]

Purpose: Specifies the degree of treatment received by pollutants at specific nodes of the drainage system.

Format: Node Pollut Result = Func

Parameters: Node Name of the node where treatment occurs. Pollut Name of pollutant receiving treatment. Result Result computed by treatment function. Choices are: C (function computes effluent concentration) R (function computes fractional removal). Func mathematical function expressing treatment result in terms of pollutant concentrations, pollutant removals, and other standard variables (see below).

Remarks: Treatment functions can be any well-formed mathematical expression involving: inlet pollutant concentrations (use the pollutant name to represent a concentration) removal of other pollutants (use R_ pre-pended to the pollutant name to represent removal) process variables which include: FLOW for flow rate into node (user’s flow units) DEPTH for water depth above node invert (ft or m) AREA for node surface area (ft2 or m2) DT for routing time step (seconds) HRT for hydraulic residence time (hours)

Any of the following math functions can be used in a treatment function: abs(x) for absolute value of x sgn(x) which is +1 for x >= 0 or -1 otherwise step(x) which is 0 for x <= 0 and 1 otherwise sqrt(x) for the square root of x log(x) for logarithm base e of x log10(x) for logarithm base 10 of x exp(x) for e raised to the x power the standard trig functions (sin, cos, tan, and cot) the inverse trig functions (asin, acos, atan, and acot) the hyperbolic trig functions (sinh, cosh, tanh, and coth) along with the standard operators +, -, *, /, ^ (for exponentiation ) and any level of nested parentheses.

Examples: ; 1-st order decay of BOD Node23 BOD C = BOD * exp(-0.05*HRT)

; lead removal is 20% of TSS removal Node23 Lead R = 0.2 * R_TSS

Section: [INFLOWS]

Purpose: Specifies external hydrographs and pollutographs that enter the drainage system at specific nodes.

Formats: Node FLOW Tseries (FLOW (1.0 Sfactor Base Pat)) Node Pollut Tseries (Type (Mfactor Sfactor Base Pat))

Parameters: Node name of the node where external inflow enters. Pollut name of a pollutant. Tseries name of a time series in the [TIMESERIES] section describing how external flow or pollutant loading varies with time. Type CONCEN if pollutant inflow is described as a concentration, MASS if it is described as a mass flow rate (default is CONCEN). Mfactor the factor that converts the inflow’s mass flow rate units into the project’s mass units per second, where the project’s mass units are those specified for the pollutant in the [POLLUTANTS] section (default is 1.0 - see example below). Sfactor a scaling factor that multiplies the recorded time series values (default is 1.0). Base a constant baseline value added to the time series value (default is 0.0). Pat name of an optional time pattern in the [PATTERNS] section used to adjust the baseline value on a periodic basis.

Remarks: External inflows are represented by both a constant and time varying component as follows: Inflow = (Baseline value)*(Pattern factor) + (Scaling factor)*(Time series value) If an external inflow of a pollutant concentration is specified for a node, then there must also be an external inflow of FLOW provided for the same node, unless the node is an Outfall. In that case a pollutant can enter the system during periods when the outfall is submerged and reverse flow occurs. External pollutant mass inflows do not require a FLOW inflow.

Examples: ; NODE2 receives flow inflow from time series N2FLOW ; and TSS concentration from time series N2TSS NODE2 FLOW N2FLOW NODE2 TSS N33TSS CONCEN

; NODE65 has a mass inflow of BOD from time series N65BOD ; listed in lbs/hr (126 converts lbs/hr to mg/sec) NODE65 BOD N65BOD MASS 126

; Flow inflow to Node N176 consists of the flow time series ; FLOW_176 scaled at 0.5 plus a baseline flow of 12.7 ; adjusted by pattern FlowPat N176 FLOW FLOW_176 FLOW 1.0 0.5 12.7 FlowPat

Section: [DWF]

Purpose: Specifies dry weather flow and its quality entering the drainage system at specific nodes.

Format: Node Type Base (Pat1 Pat2 Pat3 Pat4)

Parameters: Node name of a node where dry weather flow enters. Type keyword FLOW for flow or a pollutant name for a quality constituent. Base average baseline value for corresponding constituent (flow or concentration units). Pat1,
Pat2, etc. names of up to four time patterns appearing in the [PATTERNS] section.

Remarks: The actual dry weather input will equal the product of the baseline value and any adjustment factors supplied by the specified patterns. (If not supplied, an adjustment factor defaults to 1.0.) The patterns can be any combination of monthly, daily, hourly and weekend hourly patterns, listed in any order. See the [PATTERNS] section for more details.

Section: [RDII]

Purpose: Specifies the parameters that describe rainfall-dependent infiltration and inflow (RDII) entering the drainage system at specific nodes.

Format: Node UHgroup SewerArea

Parameters: Node name of a node receiving RDII flow. UHgroup name of an RDII unit hydrograph group appearing in the [HYDROGRAPHS] section. SewerArea area of the sewershed that contributes RDII to the node (acres or hectares).

Section: [HYDROGRAPHS]

Purpose: Specifies the shapes of the triangular unit hydrographs that determine the amount of rainfall-dependent infiltration and inflow (RDII) entering the drainage system.

Format: Name Raingage Name Month SHORT/MEDIUM/LONG R T K (Dmax Drec D0)

Remarks: Name name assigned to a unit hydrograph group. Raingage name of the rain gage used by the unit hydrograph group. Month month of the year (e.g., JAN, FEB, etc. or ALL for all months). R response ratio for the unit hydrograph. T time to peak (hours) for the unit hydrograph. K recession limb ratio for the unit hydrograph. Dmax maximum initial abstraction depth available (in rain depth units). Drec initial abstraction recovery rate (in rain depth units per day) D0 initial abstraction depth already filled at the start of the simulation (in rain depth units).

Remarks: For each group of unit hydrographs, use one line to specify its rain gage followed by as many lines as are needed to define each unit hydrograph used by the group throughout the year. Three separate unit hydrographs, that represent the short-term, medium-term, and long-term RDII responses, can be defined for each month (or all months taken together). Months not listed are assumed to have no RDII. The response ratio (R) is the fraction of a unit of rainfall depth that becomes RDII. The sum of the ratios for a set of three hydrographs does not have to equal 1.0. The recession limb ratio (K) is the ratio of the duration of the hydrograph’s recession limb to the time to peak (T) making the hydrograph time base equal to T*(1+K) hours. The area under each unit hydrograph is 1 inch (or mm).

The optional initial abstraction parameters determine how much rainfall is lost at the start of a storm to interception and depression storage. If not supplied then the default is no initial abstraction.

Lines are processed in the order they appear, and an entry for ALL assigns its values to every month of the year. An ALL entry therefore overrides any month-specific values entered on earlier lines (e.g., if entries appear in the order JAN through SEP, ALL, OCT, NOV, DEC, the ALL entry replaces the values entered for JAN through SEP, leaving only OCT, NOV, and DEC with their own values). Whenever parameters for the same month and response type are supplied more than once, the values entered last are used and WARNING 13 is written to the status report.

Example: ; All three unit hydrographs in this group have the same shapes except those in July, ; which have only a short- and medium-term response and a different shape. UH101 RG1 UH101 ALL SHORT 0.033 1.0 2.0 UH101 ALL MEDIUM 0.300 3.0 2.0 UH101 ALL LONG 0.033 10.0 2.0 UH101 JUL SHORT 0.033 0.5 2.0 UH101 JUL MEDIUM 0.011 2.0 2.0

Section: [CURVES]

Purpose: Describes a relationship between two variables in tabular format.

Format: Name Type Name X-value Y-value ...

Parameters: Name name assigned to the curve. Type the type of curve being defined: STORAGE / SHAPE / DIVERSION / TIDAL / PUMP1 / PUMP2 / PUMP3 / PUMP4 / PUMP5 / RATING / CONTROL / WEIR. X-value an X (independent variable) value. Y-value the Y (dependent variable) value corresponding to X.

Remarks: Each curve should have its name and type on the first line with its data points entered on subsequent lines. Multiple pairs of x-y values can appear on a line. If more than one line is needed, repeat the curve's name on subsequent lines. X-values must be entered in increasing order. Choices for curve type have the following meanings (flows are expressed in the user’s choice of flow units set in the [OPTIONS] section): STORAGE surface area in ft2 (m2) versus depth in ft (m) for a storage unit node SHAPE width versus depth for a custom closed cross-section, both normalized with respect to full depth DIVERSION diverted outflow versus total inflow for a flow divider node or a Custom inlet TIDAL water surface elevation in ft (m) versus hour of the day for an outfall node PUMP1 pump outflow versus increment of inlet node volume in ft3 (m3) PUMP2 pump outflow versus increment of inlet node depth in ft (m) PUMP3 pump outflow versus head difference between outlet and inlet nodes in ft (m) that has decreasing flow with increasing head PUMP4 pump outflow versus continuous inlet node depth in ft (m) PUMP5 pump outflow versus head difference between outlet and inlet nodes in ft (m) that has decreasing flow with increasing head RATING flow versus head in ft (m) for an Outlet link or a Custom inlet CONTROL control setting for a pump or flow regulator versus a controller variable (such as a node water level) in a modulated control; flow adjustment setting versus head for an LID unit’s underdrain WEIR discharge coefficient for flow in CFS (CMS) versus head in ft (m)

Remarks: See CHAPTER 1 - The Conceptual Model for illustrations of the different types of pump curves.

Examples: ; Storage curve (x = depth, y = surface area) AC1 STORAGE AC1 0 1000 2 2000 4 3500 6 4200 8 5000

; Type 1 pump curve (x = inlet wet well volume, y = flow) PC1 PUMP1 PC1 100 5 300 10 500 20

; Type 5 pump curve (x = pump head, y = pump flow) PC2 PUMP5 PC2 0 4 PC2 4 2 PC2 6 0

Section: [TIMESERIES]

Purpose: Describes how a quantity varies over time.

Formats: Name ( Date ) Hour Value ... Name Time Value ... Name FILE Fname

Parameters: Name name assigned to the time series. Date date in Month/Day/Year format (e.g., June 15, 2001 would be 6/15/2001). Hour 24-hour military time (e.g., 8:40 pm would be 20:40) relative to the last date specified (or to midnight of the starting date of the simulation if no previous date was specified). Time hours since the start of the simulation, expressed as a decimal number or as hours:minutes (where hours can be greater than 24). Value a value corresponding to the specified date and time. Fname the name of a file in which the time series data are stored

Remarks: There are two options for supplying the data for a time series: directly within this input file section as described by the first two formats through an external data file named with the third format. When direct data entry is used, multiple date-time-value or time-value entries can appear on a line. If more than one line is needed, the table's name must be repeated as the first entry on subsequent lines. When an external file is used, each line in the file must use the same formats listed above, except that only one date-time-value (or time-value) entry is allowed per line. Any line that begins with a semicolon is considered a comment line and is ignored. Blank lines are also permitted. Enclose the external file name in double quotes if it contains spaces and include its full path if it resides in a different directory than the SWMM input file.

New in OpenSWMM v6: The external file may also be a multi-column series file — a comma- or tab-delimited file with a header row whose first column holds a full date-time, or a PCSWMM .tsf file (tab-delimited with an IDs: header and 12-hour AM/PM date-times). Select a column by appending a colon and the column's header name to the file path, e.g. TS_EAST FILE "rain_2024.csv:EAST_GAGE". Without a column name the first data column is used. A single multi-column file can supply any number of time series and rain gages and is read from disk only once per model open. The format (CSV/TSV/TSF) is detected automatically from the file's contents.

There are two options for describing the occurrence time of time series data:
as calendar date plus time of day (which requires that at least one date, at the start of the series, be entered)
as elapsed hours since the start of the simulation. For the first method, dates need only be entered at points in time when a new day occurs. For rainfall time series, it is only necessary to enter periods with non-zero rainfall amounts. SWMM interprets the rainfall value as a constant value lasting over the recording interval specified for the rain gage which utilizes the time series. For all other types of time series, SWMM uses interpolation to estimate values at times that fall in between the recorded values.

Examples: ; Hourly rainfall time series with dates specified using ; one data point per line to emphasize when dates change TS1 6-15-2001 7:00 0.1 TS1 8:00 0.2 TS1 9:00 0.05 TS1 10:00 0 TS1 6-21-2001 4:00 0.2 TS2 5:00 0 TS2 14:00 0.1 TS2 15:00 0

;Inflow hydrograph - time relative to start of simulation HY1 0 0 1.25 100 2:30 150 3.0 120 4.5 0 HY1 32:10 0 34.0 57 35.33 85 48.67 24 50 0

Section: [PATTERNS]

Purpose: Specifies time patterns of dry weather flow or quality in the form of adjustment factors applied as multipliers to baseline values.

Format: Name MONTHLY Factor1 Factor2 ... Factor12 Name DAILY Factor1 Factor2 ... Factor7 Name HOURLY Factor1 Factor2 ... Factor24 Name WEEKEND Factor1 Factor2 ... Factor24

Parameters: Name name used to identify the pattern. Factor1, Factor2, etc. multiplier values.

Remarks: The MONTHLY format is used to set monthly pattern factors for dry weather flow constituents. The DAILY format is used to set dry weather pattern factors for each day of the week, where Sunday is day 1. The HOURLY format is used to set dry weather factors for each hour of the day starting from midnight. If these factors are different for weekend days than for weekday days then the WEEKEND format can be used to specify hourly adjustment factors just for weekends. More than one line can be used to enter a pattern’s factors by repeating the pattern’s name (but not the pattern type) at the beginning of each additional line. The pattern factors are applied as multipliers to any baseline dry weather flows or quality concentrations supplied in the [DWF] section.

Examples: ; Day of week adjustment factors D1 DAILY 0.5 1.0 1.0 1.0 1.0 1.0 0.5 D2 DAILY 0.8 0.9 1.0 1.1 1.0 0.9 0.8 ; Hourly adjustment factors H1 HOURLY 0.5 0.6 0.7 0.8 0.8 0.9 H1 1.1 1.2 1.3 1.5 1.1 1.0 H1 0.9 0.8 0.7 0.6 0.5 0.5 H1 0.5 0.5 0.5 0.5 0.5 0.5

Section: [VIRTUAL_JUNCTIONS]

Purpose: Declares junction nodes that exist only to join two conduits, with no physical structure of their own.

Format: Name

Parameters: Name name of a junction declared in the [JUNCTIONS] section.

Remarks: One token per line. Invert elevation and maximum depth are not read here — they are derived from the two attached conduits after parsing, so a virtual junction never imposes a node geometry of its own on the solution. Supplying any extra token is a parse error (ERROR 609).

This section has no counterpart in SWMM 5.

Section: [INLET_JUNCTIONS]

Purpose: Declares a virtual junction that also carries a street inlet, combining the [VIRTUAL_JUNCTIONS] and [INLET_USAGE] roles in one row.

Format: Name Elev MaxDepth Inlet CaptureNode (Number Clogged Qmax aLocal wLocal Placement)

Parameters: Name name of the node. Elev invert elevation (ft or m). MaxDepth maximum depth, i.e. the street's flood depth (ft or m). Inlet name of an inlet design in the [INLETS] section. CaptureNode name of the node that receives the captured flow. Number number of inlets placed (default 1). Clogged degree of clogging as a percent (default 0). Qmax maximum flow the inlet can capture (flow units; 0 or blank = no limit). aLocal height of a local gutter depression (in or mm). wLocal width of a local gutter depression (ft or m). Placement ON_GRADE, ON_SAG or AUTOMATIC (default AUTOMATIC).

Remarks: The node is marked both virtual and inlet-bearing. More than eleven tokens is a parse error (ERROR 623).

This section has no counterpart in SWMM 5.

Section: [INITIAL_QUALITY]

Purpose: Sets the initial concentration of a constituent in a node or a link at the start of the simulation.

Format: NODE Name Constituent Value LINK Name Constituent Value FILE Fname

Parameters: Name name of the node or link. Constituent name of a pollutant, or a constituent of a process component. Value initial concentration (concentration units). Fname name of a CSV file holding the same four fields per line.

Remarks: The scope keyword must be NODE or LINK; anything else is a parse error. A row with fewer than four tokens is a parse error.

The FILE form names a sidecar whose lines are scope,element,constituent,value, with an optional header row. It is resolved relative to the input file's directory and read when the model is opened, so it may be written by a pre-processor that does not have to rewrite the .inp.

Section: [RDII_DECAY]

Purpose: Applies a seasonal decay to an RDII unit hydrograph group, so that the same hydrograph produces less inflow as antecedent conditions dry out.

Format: UHgroup Response Kdep K0 KT Tref ThetaRec Tfreeze

Parameters: UHgroup name of a unit hydrograph group in the [HYDROGRAPHS] section. Response SHORT, MEDIUM or LONG — which of the group's three response terms this row applies to. Kdep depletion rate coefficient (1/day). K0 base recovery rate coefficient (1/day). KT temperature coefficient of the recovery rate (1/day per degree). Tref reference temperature for KT (deg F or deg C). ThetaRec recovery threshold as a fraction. Tfreeze temperature below which recovery stops (deg F or deg C).

Remarks: A row with fewer than eight tokens is ignored, as is a row whose Response keyword is not one of the three accepted values or whose Kdep, K0 or KT is negative.

This section has no counterpart in SWMM 5.

Section: [EVENTS]

Purpose: Restricts reporting to one or more time windows, so that a long continuous run writes output only for the periods of interest.

Format: StartDate StartTime EndDate EndTime

Parameters: StartDate date on which the event begins (MM/DD/YYYY). StartTime time of day at which it begins (HH:MM:SS). EndDate date on which it ends. EndTime time of day at which it ends.

Remarks: A row with fewer than four tokens is ignored, as is any row whose start is not earlier than its end. Events do not change the simulation period in the [OPTIONS] section; the model still runs continuously.

Section: [TAGS]

Purpose: Attaches a free-text category label to an object, for grouping and filtering.

Format: ObjectType Name Tag

Parameters: ObjectType NODE, LINK or SUBCATCH. Name name of the object. Tag the label. Use double quotes if it contains spaces.

Remarks: A row with fewer than three tokens is ignored, as is a row naming an object that does not exist. Tags are stored against the object's position rather than its name, so renaming the object keeps its tag.

Section: [PROFILE]

Purpose: Names a sequence of links that form a profile path, for a graphical client to plot.

Format: Name Link1 Link2 ...

Remarks: The engine preserves the authored lines for the writer without interpreting or validating the profile path. This section has no effect on the simulation. [PROFILES] is an accepted alias.

Section: [PROFILES]

Purpose: Alternate spelling of Section: [PROFILE], with the same Name Link1 Link2 ... format.

Remarks: The writer preserves the section spelling: rows read from [PROFILES] are written under [PROFILES], and rows read from [PROFILE] remain under [PROFILE]. Neither spelling changes the simulation.

Section: [USER_FLAGS]

Purpose: Declares a user-defined attribute that can then be given per-object values in the [USER_FLAG_VALUES] section.

Format: Name Type (Description)

Parameters: Name name of the flag. Stored upper-case, so flag names are case-insensitive. Type BOOLEAN, INTEGER, REAL or STRING. Description optional free text; quote it if it contains spaces.

Remarks: A row with fewer than two tokens is ignored. An unrecognised Type is treated as STRING and raises WARNING 102.

This section has no counterpart in SWMM 5.

Section: [USER_FLAG_VALUES]

Purpose: Assigns a value for a user-defined flag to one object.

Format: ObjectType Name FlagName Value

Parameters: ObjectType NODE, LINK or SUBCATCH. Name name of the object; case is preserved. FlagName name of a flag declared in [USER_FLAGS]; matched case-insensitively. Value the value, parsed according to the flag's declared type.

Remarks: A row with fewer than four tokens is ignored. Assigning a value for a flag that was never declared is accepted, treated as STRING, and raises WARNING 103 — so ordering the two sections the wrong way round degrades the type rather than failing the run.

This section has no counterpart in SWMM 5.

Section: [PLUGINS]

Purpose: Loads a plugin shared library at start-up.

Format: Path (Arg1 Arg2 ...)

Parameters: Path path to the plugin library. Relative paths resolve against the plugin search path. Arg optional initialisation arguments passed to the plugin verbatim.

Remarks: See CHAPTER 5 - Programmatic C API; Python Bindings and Plugins for what a plugin can do and where libraries are discovered.

This section has no counterpart in SWMM 5.

Section: [PROCESS_COMPONENTS]

Purpose: Attaches a process component — an advection-reaction-dispersion solver, a reaction system, water age or heat transport — to the simulation.

Format: Id key="value" key="value" ...

Parameters: Id identifier of the component. key="value" configuration arguments. The reserved key CONFIG names a configuration file for the component; every other key is passed through to it.

Remarks: An argument that is not a key="value" pair is a parse error naming the component and the offending token.

This section has no counterpart in SWMM 5.

2.3 Map Data Section

SWMM’s graphical user interface (GUI) can display a schematic map of the drainage area being analyzed. This map displays subcatchments as polygons, nodes as circles, links as polylines, and rain gages as bitmap symbols. In addition it can display text labels and a backdrop image, such as a street map. The GUI has tools for drawing, editing, moving, and displaying these map elements.

The map’s coordinate data are stored in the format described below. Normally these data are simply appended to the SWMM input file by the GUI so users do not have to concern themselves with it. However it is sometimes more convenient to import map data from some other source, such as a CAD or GIS file, rather than drawing a map from scratch using the GUI. In this case the data can be added to the SWMM project file using any text editor or spreadsheet program. SWMM does not provide any automated facility for converting coordinate data from other file formats into the SWMM map data format.

SWMM's map data are organized into the following seven sections: [MAP] X,Y coordinates of the map’s bounding rectangle [POLYGONS] X,Y coordinates for each vertex of subcatchment polygons [COORDINATES] X,Y coordinates for nodes [VERTICES] X,Y coordinates for each interior vertex of polyline links [LABELS] X,Y coordinates and text of labels [SYMBOLS] X,Y coordinates for rain gages [BACKDROP] X,Y coordinates of the bounding rectangle and file name of the backdrop image. Figure D-2 displays a sample map and Figure D-3 the data that describes it. Note that only one link, 3, has interior vertices which give it a curved shape. Also observe that this map’s coordinate system has no units, so that the positions of its objects may not necessarily coincide to their real-world locations.

Figure D-2 Example study area map

Figure D-3 Data for example study area map

A detailed description of each map data section will now be given. Remember that map data are only used as a visualization aid for SWMM’s GUI and they play no role in any of the runoff or routing computations. Map data are not needed for running the command line version of SWMM.

Section: [MAP]

Purpose: Provides dimensions and distance units for the map.

Formats: DIMENSIONS X1 Y1 X2 Y2 UNITS FEET / METERS / DEGREES / NONE

Parameters: X1 lower-left X coordinate of full map extent Y1 lower-left Y coordinate of full map extent X2 upper-right X coordinate of full map extent

Y2 upper-right Y coordinate of full map extent

Section: [COORDINATES]

Purpose: Assigns X,Y coordinates to drainage system nodes.

Format: Node Xcoord Ycoord

Parameters: Node name of node. Xcoord horizontal coordinate relative to origin in lower left of map.

Ycoord vertical coordinate relative to origin in lower left of map.

Section: [VERTICES]

Purpose: Assigns X,Y coordinates to interior vertex points of curved drainage system links.

Format: Link Xcoord Ycoord

Parameters: Link name of link. Xcoord horizontal coordinate of vertex relative to origin in lower left of map. Ycoord vertical coordinate of vertex relative to origin in lower left of map.

Remarks: Include a separate line for each interior vertex of the link, ordered from the inlet node to the outlet node.

Straight-line links have no interior vertices and therefore are not listed in this section.

Section: [POLYGONS]

Purpose: Assigns X,Y coordinates to vertex points of polygons that define a subcatchment boundary.

Format: Subcat Xcoord Ycoord

Parameters: Subcat name of subcatchment. Xcoord horizontal coordinate of vertex relative to origin in lower left of map. Ycoord vertical coordinate of vertex relative to origin in lower left of map.

Remarks:

Include a separate line for each vertex of the subcatchment polygon, ordered in a consistent clockwise or counter-clockwise sequence.

Section: [SYMBOLS]

Purpose: Assigns X,Y coordinates to rain gage symbols.

Format: Gage Xcoord Ycoord

Remarks: Gage name of rain gage. Xcoord horizontal coordinate relative to origin in lower left of map.

Ycoord vertical coordinate relative to origin in lower left of map.

Section: [LABELS]

Purpose: Assigns X,Y coordinates to user-defined map labels.

Format: Xcoord Ycoord Label (Anchor Font Size Bold Italic)

Parameters: Xcoord horizontal coordinate relative to origin in lower left of map. Ycoord vertical coordinate relative to origin in lower left of map. Label text of label surrounded by double quotes. Anchor name of node or subcatchment that anchors the label on zoom-ins (use an empty pair of double quotes if there is no anchor). Font name of label’s font (surround by double quotes if the font name includes spaces). Size font size in points. Bold YES for bold font, NO otherwise. Italic YES for italic font, NO otherwise.

Remarks: Use of the anchor node feature will prevent the label from moving outside the viewing area when the map is zoomed in on.

If no font information is provided then a default font is used to draw the label.

Section: [BACKDROP]

Purpose: Specifies file name and coordinates of map’s backdrop image.

Formats: FILE Fname DIMENSIONS X1 Y1 X2 Y2

Parameters: Fname name of file containing backdrop image X1 lower-left X coordinate of backdrop image Y1 lower-left Y coordinate of backdrop image X2 upper-right X coordinate of backdrop image Y2 upper-right Y coordinate of backdrop image

2.4 Two-Dimensional Surface and Groundwater Sections

The twenty-one [2D_*] sections configure the two-dimensional overland surface of Chapter 9: Two-Dimensional Overland Flow Analysis — its mesh, coupling to the network, boundary conditions, per-cell infiltration and evaporation, the aquifer beneath it, and surface quality — and the six [GW_*] sections carry the groundwater-transport grammar, which this release parses, validates and writes back but does not solve. Every row grammar below follows the parser; where the design notes in plans/2D_INPUT_FORMAT_SPEC.md and the parser disagree, the parser wins and the entry says so.

Section: [2D_OPTIONS]

Purpose: Sets the options of the two-dimensional overland-flow module: the momentum closure and marcher controls, the wetting and drying thresholds, the coupling to the one-dimensional network, how rainfall, evaporation and infiltration reach the mesh, the groundwater and transport process enables, and the 2D results file.

Format:

Keyword Value

One keyword per line. Keywords are matched case-insensitively; an unknown keyword is a parse error (Unknown 2D_OPTIONS parameter). The value of REPORT_2D_VARIABLES and REPORT_2D_SPECIES may span several tokens; every other keyword reads its first value token only.

Parameters:

Solver

Keyword	Values	Default	Description
MOMENTUM_EQUATION	LOCAL_INERTIAL (LI) / FULL_SWE (SWE, FULL) / DIFFUSIVE_WAVE (DW, DIFFUSIVE)	LOCAL_INERTIAL	Face law of the explicit marcher. LOCAL_INERTIAL is the de Almeida and Bates update; FULL_SWE is the conservative shallow-water form with the convective term (hydrostatic reconstruction, rotated HLLC flux, shock capturing); DIFFUSIVE_WAVE is the Manning quasi-steady flux with no inertia.
INTEGRATOR	EXPLICIT	EXPLICIT	The explicit marcher is the only 2D integrator. Any other value is a retired selection (see the Retired keys table).
RECONSTRUCTION_ORDER	1 / 2	1	FULL_SWE only. 1 is piecewise constant (first-order Godunov, forward Euler); 2 reconstructs (eta, h, u, v), using limited Green-Gauss gradients in connected wet interiors and a conditioned eta/depth fit with cell-centred velocity at shorelines; SSP-RK2 uses global stepping (LTS_TIERS is reduced to 1 with a warning). Active surface transport falls back to order 1; groundwater RK2 supports only standalone CPU passive pollutant/age CLOSED_FORM/ENSLAVED/SIGMA with authored wells and HEAD/FLOW edges (Hydrology §9.11). See CHAPTER 7 — Two-Dimensional CPU Implementation and Qualification and Chapter 9: Two-Dimensional Overland Flow Analysis §9.5.10.
THETA	(0, 1]	0.8	Face-update weighting of the local-inertial law: 1 is the pure Bates 2010 update, below 1 blends the reconstructed neighbour discharge to damp thin-film checkerboarding.
THETA_REFERENCE_STEP	finite seconds ≥ 0	0	Zero applies THETA on each face firing. A positive interval makes THETA the retention over that many seconds; each face uses `theta_eff = exp(log(THETA)*dt_face/reference_step)`. The actual local face step and window tails are used. THETA=1 disables blending. Positive values persist in model files and checkpoint identities; zero is omitted by the writer.
FROUDE_MAX	> 0	1.5	Clamp on the face Froude number of the local-inertial law.
CELL_CLOSURE	FLAT / VFR	FLAT	Volume-to-free-surface closure of a cell. FLAT is the flat-cell relation; VFR is the planar-bed volume/free-surface relationship, which restores the lake-at-rest property at shorelines at the cost of more substeps.
FACE_RECONSTRUCTION	MEAN / VFR_FACE	MEAN	Conveyance depth at a shared edge. MEAN uses the upwind cell-mean depth; VFR_FACE reconstructs the wetted depth over the edge's own endpoint elevations, so a crest resolved as a line of high vertices blocks flow until the water reaches it.
VFR_MIN_WET_FRAC	(0, 0.5]	0.01	Wetted-area-fraction floor of the regularised VFR closure. Used only under CELL_CLOSURE VFR.
FLUX_DH_EPS	number, metres	0.004	Head-difference floor below which the diffusive flux is linearised. 0 restores the bare square root. Always metres.
LIMITER_EPSILON	number	1.0e-6	Regularisation of the slope limiter applied to the reported gradient fields.
ADVECTION	YES / ON / TRUE / NO / OFF / FALSE	NO	Deprecated spelling of MOMENTUM_EQUATION FULL_SWE (2026-09-06). Still honoured so an old deck keeps its physics; a file load warns and names the replacement.
BACKEND	AUTO / CPU / OMP / CUDA / HIP / SYCL	AUTO	Which marcher implementation runs the mesh. CPU is the built-in host marcher; OMP, CUDA, HIP and SYCL name a Kokkos plugin and bypass the mesh-size floors (an absent plugin or device falls back to CPU with a notice). AUTO picks a device plugin above the device floor, the OpenMP plugin above its own floor, else CPU. The OPENSWMM_2D_BACKEND environment variable overrides the key.

Optional rotating flow and horizontal mixing

These processes require CPU FULL_SWE with LTS_TIERS 1 and uncoupled surface hydraulics; active groundwater, transport, heat, snow or 1D node coupling is refused. Defaults leave both processes disabled. See Chapter 9: Two-Dimensional Overland Flow Analysis for the momentum sources, numerical qualification and limitations.

Keyword	Values	Default	Description
CORIOLIS	OFF / LATITUDE / CONSTANT_F	OFF	Selects no rotation, a Coriolis parameter computed from latitude, or a directly authored parameter. LATITUDE requires CORIOLIS_LATITUDE; CONSTANT_F requires CORIOLIS_F.
CORIOLIS_LATITUDE	finite degrees north in [-90, 90] / UNSET	Unset	Latitude used in LATITUDE mode; UNSET clears the authored value. Inactive values remain stored.
CORIOLIS_F	finite number, s⁻¹ / UNSET	Unset	Signed Coriolis parameter used in CONSTANT_F mode; UNSET clears the authored value. Inactive values remain stored.
TURBULENCE_MODEL	NONE / SMAGORINSKY / MIXING_LENGTH	NONE	Selects no horizontal mixing, conservative depth-integrated Smagorinsky momentum mixing (filter width from cell area), or the same operator with a shear-based depth mixing length (vorticity times a length set by water depth, capped near boundaries). This does not add scalar turbulent diffusivity or a wall-damping model.
SMAGORINSKY_CS	finite dimensionless number ≥ 0	0.10	Smagorinsky coefficient, used with filter width equal to the square root of cell area; 0 gives zero eddy viscosity. Only active under TURBULENCE_MODEL SMAGORINSKY.
EDDY_VISCOSITY_BACKGROUND	finite number ≥ 0, m²/s	0	Constant horizontal eddy viscosity ν0 added to the closure's eddy viscosity (SMAGORINSKY or MIXING_LENGTH). It is a user parameter, not a calibrated constant: it does not scale with depth, velocity or model size. Inactive under TURBULENCE_MODEL NONE; an inactive value remains stored.
MIXING_LENGTH_COEFFICIENT	finite dimensionless number ≥ 0	0.5	Coefficient c of the mixing length l = min(c·h, κ·d) used by TURBULENCE_MODEL MIXING_LENGTH, where h is the cell depth, κ = 0.41 and d the distance to the nearest mesh boundary edge; νt = ν0 + l² times the vorticity magnitude in each cell. The default 0.5 is the depth-averaged horizontal mixing length reported by Stansby (2003, 2006). Only active under MIXING_LENGTH; an inactive value remains stored.

Time control

Keyword	Values	Default	Description
MAX_TIMESTEP	number, seconds	10.0	Cap on the marcher step. Also caps the spread of the local-time-stepping tiers and the co-advance batch span.
CFL_NUMBER	(0, 1]	0.7	Courant fraction of the marcher step. 1.0 is the linear stability limit; the default keeps a 30 percent margin.
LTS_TIERS	1 .. 8	4	Number of local-time-stepping tiers. 1 forces one global step for every cell.

Wetting and drying

Keyword	Values	Default	Description
DRY_DEPTH	number, metres	0.001	Depth below which a cell is dry. Also drives the coupling and outfall wet ramps and the evaporation taper. Always metres.
H_MOVE	>= 0, metres	0.003	Flux-activation depth: a cell below it is source-only (rain accumulates, no face flux). The on/off hysteresis band is the smaller of 1 mm and half of H_MOVE. Always metres.
FRONT_REBUILD	AUTO / YES / ON / NO / OFF	AUTO	Rebuild the flux-active set as soon as a wetting front reaches the edge of the active halo instead of waiting for the fixed rebuild cadence. AUTO is YES for FULL_SWE and DIFFUSIVE_WAVE and NO for LOCAL_INERTIAL.

Coupling to the 1D network

Keyword	Values	Default	Description
COUPLING_CD	number	0.65	Discharge coefficient of every coupling row that does not author its own CD.
COUPLING_AREA	AUTO / DEFAULT	DEFAULT	AUTO derives the exchange area of each coupling row that did not author an AREA from the largest connected conduit (1.25 times its full-flow area, clamped to 0.05 .. 2.0 square metres). DEFAULT keeps the authored or default area.
COUPLING_SYNC	>= 0, seconds	0	0 co-advances the 2D domain every routing step. A positive value batches the 2D advance over roughly that span (clamped at run time to the routing step .. 60 s); the held-exchange error grows with the span.
COUPLING_IN_FLOODING	YES / TRUE / NO / FALSE	NO	YES books the 1D-to-2D spill into the 1D report's Flooding Loss row instead of its own 2D Coupling Outflow row. Changes the report only; routed volumes are identical.
COUPLING_LAW	ORIFICE / WEIR_ORIFICE	ORIFICE	Exchange law for junction/storage coupling points. WEIR_ORIFICE selects the structure-aware weir/orifice law; a node's LAW in [2D_NODE_COUPLING] overrides this choice.
COUPLING_HEAD	CELL / VERTEX / STENCIL_WET_MEAN	CELL	Surface head sampled for coupling: the mapped cell, vertex reconstruction, or wet-cell stencil mean.
COUPLING_COEFFS	DEFAULT / RUBINATO2017 / RUBINATO2017_LOWER / RUBINATO2017_UPPER	DEFAULT	Coefficient preset for WEIR_ORIFICE. A node's COEFFS and individual CW, CSW, COI and COO values override the global preset; an authored legacy map-row Cd overrides both orifice coefficients.
COUPLING_POND_MODE	FOOTPRINT / CHAMBER / TRACKING	FOOTPRINT	Above-rim pond-area policy: the mapped surface footprint, the 1D chamber area, or a relaxed tracking area.
COUPLING_POND_RELAX	>= 0, seconds	0	Relaxation time for TRACKING; 0 selects five routing steps.
COUPLING_RIM_BAND	DEFAULT or >= 0, metres	DEFAULT	Height above the rim over which pond area ramps in smoothly. DEFAULT selects 0 for FOOTPRINT and 0.05 m for CHAMBER or TRACKING. Always metres.
COUPLING_EQUALIZE	YES / NO / DEFAULT	DEFAULT	Caps an exchange so one coupling window cannot carry the 1D and 2D heads past each other. DEFAULT enables the cap for WEIR_ORIFICE and disables it for ORIFICE.

Rainfall, evaporation and infiltration

Keyword	Values	Default	Description
RAINFALL_MODE	NATURAL_NEIGHBOUR (NATURAL_NEIGHBOR) / NEAREST_NEIGHBOUR (NEAREST_NEIGHBOR) / SYSTEM / NONE	NATURAL_NEIGHBOUR	How rain gage rainfall is mapped onto the cells: natural-neighbour interpolation of the located gages (inverse-distance outside their hull), the closest located gage (first-listed wins a tie), the uniform mean of all gages, or no rain on the mesh. Use NONE when subcatchments already capture the storm. The OPENSWMM_2D_RAINFALL_MODE environment variable overrides the key.
EVAPORATION	NO / OFF / YES / ON / FORCING / CLIMATE	YES	NO zeroes the mesh evaporation sink. YES applies only per-cell forcing supplied through the API. CLIMATE evaporates every unforced cell at the project [EVAPORATION] rate; forcing still overrides it.
INFILTRATION	YES / ON / NO / OFF / AUTO	AUTO	Process enable for mesh infiltration. AUTO runs it when any [2D_INFILTRATION_DEFAULTS] or [2D_INFILTRATION] row resolves; NO keeps the rows but deactivates them for the run; YES warns when no row resolves.
INFIL_STEP	HH:MM:SS, HH:MM or seconds	0 (unset)	Infiltration update cadence. Unset falls back to [2D_INFILTRATION_OPTIONS] INFIL_STEP, then to the project WET_STEP. When both are present this key wins.
INFIL_DEFAULT_METHOD	NONE / HORTON / MOD_HORTON / GREEN_AMPT / MOD_GREEN_AMPT / CURVE_NUMBER / CONSTANT (the legacy spellings MODIFIED_HORTON, MODIFIED_GREEN_AMPT and CURVE_NUM are accepted)	unset	Method of the mesh-wide `` row of [2D_INFILTRATION_DEFAULTS]. Unset lets that row govern; NONE drops the `` row for the run; a method must match the `*` row (its parameters live there) - a mismatch is an initialise error, a missing row a warning.
INFIL_DESTINATION	LOST / SUBCATCH_AQUIFER / AQUIFER_2D	LOST	Destination applied to every infiltration row that did not spell its own DEST column. SUBCATCH_AQUIFER recharges the legacy aquifer of the subcatchment containing the cell; AQUIFER_2D recharges the integrated two-zone aquifer and requires a resolved [2D_AQUIFER].

Groundwater

Keyword	Values	Default	Description
GROUNDWATER	YES / ON / NO / OFF / AUTO	AUTO	Process enable for the integrated 2D subsurface. AUTO runs the kernel when any [2D_AQUIFER_OPTIONS], [2D_AQUIFER] or [2D_AQUIFER_NODE] row was authored; NO keeps the rows and runs without the subsurface; YES with no rows warns.
GW_ET	NONE / CAPILLARY_RISE / BOUNDARY_ET / BOTH	NONE	Alias of the [2D_AQUIFER_OPTIONS] key of the same name. A value spelled here is folded into [2D_AQUIFER_OPTIONS] when the model opens and is never stored in two places.

Heat

Keyword	Values	Default	Description
HEAT_MODEL	TRANSPORT_ONLY / COUPLED	TRANSPORT_ONLY	COUPLED enables the mesh water/bed energy solver. Both modes require [OPTIONS] HEAT_TRANSPORT and an active temperature row; TRANSPORT_ONLY carries temperature without the coupled mesh energy model.
BED_HEAT_MODEL	NONE / LOCAL_STORAGE / GROUND_COLUMN	NONE	Selects no bed store, a finite local bed store, or a ground column. LOCAL_STORAGE cannot overlap an active aquifer; use GROUND_COLUMN for the shared porous thermal column.
HEAT_SURFACE_EXCHANGE	AUTO / YES / NO	AUTO	AUTO inherits the project heat module's surface exchange setting; YES or NO overrides it for the mesh.
HEAT_RADIATIVE_EXCHANGE	AUTO / YES / NO	AUTO	AUTO inherits the project heat module's radiative exchange setting; YES or NO overrides it for the mesh.

Transport

Keyword	Values	Default	Description
TRANSPORT_POLLUTANTS	YES / ON / NO / OFF	YES	Carry the [POLLUTANTS] species on the 2D surface. NO drops their rows from the surface transport state; the 1D side is unaffected.
TRANSPORT_MSX	YES / ON / NO / OFF	YES	Carry the reactions component's species on the 2D surface.
TRANSPORT_AGE	YES / ON / NO / OFF	YES	Carry water age on the 2D surface.
TRANSPORT_TEMPERATURE	YES / ON / NO / OFF	YES	Carry temperature on the 2D surface.
DISPERSION	>= 0, square metres per second	0	Isotropic species dispersion coefficient on the surface. 0 never enters the dispersive face term; a negative value is refused. Always SI.

Output

Keyword	Values	Default	Description
REPORT_2D	YES / 1 / NO / 0	YES	NO skips the recomputation of the reported gradient fields at each report step. It does not suppress the 2D results file.
OUTPUT_FILE	path (one token; quote a path containing spaces)	none	2D results file (HDF5, CF/UGRID), resolved relative to the input file's directory. When absent no 2D results file is written.
OUTPUT_PRECISION	FLOAT32 (F32, SINGLE) / FLOAT64 (F64, DOUBLE)	FLOAT32	Storage type of the time-varying datasets and envelopes of the results file. Mesh geometry always stays float64.
OUTPUT_COMPRESSION	0 .. 9	4	zlib level of the chunked datasets; the byte-shuffle filter precedes it whenever the level is above 0. 0 is none.
REPORT_2D_VARIABLES	DEFAULT / MINIMAL / ALL / NONE, or any list of DEPTH VELOCITY EDGE_FLUX NODE_HEAD SPECIES RAINFALL INFILTRATION COUPLING GRADIENTS CONTINUITY ENVELOPES BUILDUP GROUNDWATER GW_DETAILED HEAT	DEFAULT	Dataset groups written to the results file (space- or comma-separated; presets and tokens may be mixed). DEPTH is always included. DEFAULT is DEPTH VELOCITY EDGE_FLUX NODE_HEAD SPECIES RAINFALL INFILTRATION ENVELOPES BUILDUP GROUNDWATER; MINIMAL is DEPTH NODE_HEAD ENVELOPES. HEAT adds optional water, bed, soil, and mesh-connected LID temperature/energy/capacity fields, static LID-to-node/face/physical-layer mapping, signed cumulative LID/ground contact energy, and cumulative energy-budget fields when thermal owners are active. Contact receipts are positive into the LID layer and equal-and-opposite to the soil-side `lid_contact_j` budget. Zero-capacity LID cells report zero energy/capacity and NaN temperature. Unselected groups are not created in the file.
REPORT_2D_SPECIES	ALL, or a list of species names	ALL	Species rows written to the results file. ALL writes every row the transport layout carries.
REPORT_2D_STEP	HH:MM:SS, HH:MM or seconds	0	2D-only report interval. 0 follows [OPTIONS] REPORT_STEP; otherwise it must be a positive multiple of REPORT_STEP (checked at start).

Retired keys

Keyword	Status	Behaviour today
MIN_TIMESTEP	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
REL_TOLERANCE	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
ABS_TOLERANCE	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
MAX_CVODE_STEPS	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
MAX_KRYLOV_DIM	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
LINEAR_SOLVER	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
PRECONDITIONER	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
JACOBIAN	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
ATOL_AREA_REF	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
COUPLING_INTERVAL	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path. Superseded by COUPLING_SYNC.
COUPLING_WINDOW	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path. Superseded by COUPLING_SYNC.
ACTIVE_SET	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path. The active set is always on.
ACTIVE_SET_HALO	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path.
MOMENTUM	Retired	Ignored on file load with WARNING 104; a hard error on the programmatic option-set path. Superseded by MOMENTUM_EQUATION.
INTEGRATOR with any value other than EXPLICIT (CVODE, ARKODE)	Retired	The value is ignored on file load with WARNING 104 and the marcher runs; a hard error on the programmatic option-set path.
ADVECTION YES	Retired	Deprecated spelling of MOMENTUM_EQUATION FULL_SWE. Accepted and honoured; a file load warns and names the replacement.

Remarks: The keys marked "always metres" or "always SI" (DRY_DEPTH, H_MOVE, FLUX_DH_EPS, DISPERSION) do not follow FLOW_UNITS or the mesh's ;; UNITS: header; everything the mesh sections carry does (see [2D_VERTICES]).

WARNING 104 reads: "[2D_OPTIONS] %s was retired with the CVODE/ARKODE 2D solvers and was ignored; the explicit local-inertial marcher is the only 2D integrator."

The section may also appear in the external mesh file named by [2D_MESH_FILE]; values read there are applied after the inline ones and override them.

OUTPUT_FILE reads a single token, so a path containing spaces must be double-quoted; [2D_MESH_FILE] is the one section that rejoins an unquoted path.

INFIL_STEP here is the canonical home of the [2D_INFILTRATION_OPTIONS] value and GW_ET of the [2D_AQUIFER_OPTIONS] value; the writer emits each in its canonical section only.

The theory behind the solver, wetting and drying, coupling and reporting keys is in Chapter 9: Two-Dimensional Overland Flow Analysis (sections 9.4, 9.5, 9.7, 9.8, 9.9 and 9.11); the groundwater enables refer to hydrology Chapter 9 (mesh groundwater).

This section has no counterpart in SWMM 5.

Section: [2D_VERTICES]

Purpose: Lists the vertices of the two-dimensional mesh: their planimetric coordinates and bed elevation.

Format:

X Y Z (Tag)

Parameters: X horizontal coordinate of the vertex, in the mesh's length units (ft or m). Y vertical map coordinate of the vertex, in the mesh's length units (ft or m). Z bed elevation of the vertex, in the mesh's length units (ft or m). Tag optional name of the vertex, usable instead of its index in [2D_VERTEX_NODE_MAP].

Remarks: Vertices are numbered 0, 1, 2, ... in file order; that 0-based index is what [2D_TRIANGLES], [2D_QUADS], [2D_EDGE_CONVEYANCE] and [2D_VERTEX_NODE_MAP] refer to. A row with fewer than three numeric tokens is a parse error.

The mesh's length unit follows [OPTIONS] FLOW_UNITS (feet for CFS, GPM and MGD; metres otherwise) unless the file carries a comment line ;; UNITS: SI (m) (also accepted: m, metre, metres, meter, meters, case-insensitive), which declares the coordinates, elevations, initial depths, coupling areas and constant stages already metric and suppresses the feet-to-metres scaling at initialise. The header is looked for over the whole file, last match wins; the engine's own writer emits it under this section.

A mesh needs at least three vertices; the mesh is validated when the model initialises (see Chapter 9: Two-Dimensional Overland Flow Analysis, section 9.3).

This section has no counterpart in SWMM 5.

Section: [2D_TRIANGLES]

Purpose: Lists the triangular cells of the mesh, each with its Manning roughness and, optionally, an initial water depth and a classification tag.

Format:

V1 V2 V3 ManningsN (InitDepth) (Tag)

Parameters: V1, V2, V3 0-based indices of the three vertices, from [2D_VERTICES]. ManningsN Manning's roughness coefficient (n) of the cell. InitDepth initial water depth in the mesh's length units (ft or m); must be >= 0 (default 0 = dry). Tag optional classification name of the cell, matched by [2D_INFILTRATION_DEFAULTS] and by the TAG scope of the aquifer, quality and groundwater sections, and usable instead of the index in [2D_TRIANGLE_NODE_MAP].

Remarks: Cells are numbered 0, 1, 2, ... in file order, triangles first and then every [2D_QUADS] row; that unified 0-based index is the TRI column of [2D_INITIAL_VELOCITY], [2D_BOUNDARY_CONDITIONS] and [2D_BOUNDARY_QUALITY], and the CELL column (1-based) of the other cell-addressed sections. A triangle row that follows a quad row is a parse error.

The fifth column is ambiguous by design: when it parses as a number it is InitDepth and the sixth column is Tag; otherwise it is Tag. The engine's writer emits InitDepth on every row whenever any cell carries a depth or a tag, so files it wrote are unambiguous.

Edge k of a cell joins vertices V[(k+1) mod 3] and V[(k+2) mod 3]: edge 0 is opposite V1, edge 1 opposite V2 and edge 2 opposite V3. This is the EDGE numbering of [2D_BOUNDARY_CONDITIONS] and [2D_BOUNDARY_QUALITY].

Vertex indices must be in range and distinct, the area positive and ManningsN positive; these are checked when the model initialises, not at parse.

This section has no counterpart in SWMM 5.

Section: [2D_QUADS]

Purpose: Lists the convex quadrilateral cells of the mesh, appended after every triangle.

Format:

V1 V2 V3 V4 ManningsN (InitDepth) (Tag)

Parameters: V1, V2, V3, V4 0-based indices of the four vertices in cyclic order (either orientation). ManningsN Manning's roughness coefficient (n) of the cell. InitDepth initial water depth in the mesh's length units (ft or m); must be >= 0 (default 0 = dry). Tag optional classification name of the cell (see [2D_TRIANGLES]).

Remarks: The j-th quad row is cell number (number of triangles + j) in the unified cell index used by every cell-addressed section. Column six is InitDepth when numeric, otherwise Tag; column seven is Tag when InitDepth is present, exactly as for [2D_TRIANGLES].

Edge k of a quad joins V[(k+1) mod 4] and V[(k+2) mod 4]: edge 0 = (V2, V3), edge 1 = (V3, V4), edge 2 = (V4, V1), edge 3 = (V1, V2). Non-convex or self-intersecting quads fail validation at initialise.

The section is written only when the mesh holds quads; an all-triangle file is unchanged. See Chapter 9: Two-Dimensional Overland Flow Analysis, section 9.11b.

This section has no counterpart in SWMM 5.

Section: [2D_MESH_FILE]

Purpose: Names an external file that holds the mesh and the other 2D sections instead of, or in addition to, the main input file.

Format:

FILE Path

Parameters: Path absolute path, or a path relative to the directory of the input file. Surrounding double quotes are stripped; an unquoted path containing spaces is rejoined from its tokens.

Remarks: Only the first FILE line of the section is read. The conventional extension is .2dm, but the file is plain input-file text: any of [2D_OPTIONS], [2D_VERTICES], [2D_TRIANGLES], [2D_QUADS], [2D_INITIAL_VELOCITY], [2D_VERTEX_NODE_MAP], [2D_TRIANGLE_NODE_MAP], [2D_BOUNDARY_CONDITIONS], [2D_EDGE_CONVEYANCE], [2D_INITIAL_QUALITY], [2D_INITIAL_BED_QUALITY], [2D_BOUNDARY_QUALITY], [2D_INFILTRATION_OPTIONS], [2D_INFILTRATION_DEFAULTS] and [2D_INFILTRATION], with the same grammar as here. It may not contain [2D_MESH_FILE] itself, and it does not carry the aquifer, coverage, loading, curb-length or [GW_*] sections, which stay in the main file.

The external file is parsed after the main file. Per section, the external file wins: a section present in both replaces the inline rows rather than adding to them, and its [2D_OPTIONS] values override inline ones. Its own ;; UNITS: header is honoured (see [2D_VERTICES]). A missing or unreadable file is fatal when the model is opened for a run.

When a mesh file is set, the writer emits only [2D_OPTIONS] and this section into the input file and rewrites the current mesh to the external file. The file slot is described in CHAPTER 3 - Files and Command-Line Operation.

This section has no counterpart in SWMM 5.

Section: [2D_VERTEX_NODE_MAP]

Purpose: Couples a mesh vertex to a node of the one-dimensional network, so that water is exchanged between the cells around the vertex and the node.

Format:

Vertex Node (Cd) (Area)

Parameters: Vertex 0-based index of a vertex, or its Tag from [2D_VERTICES]. Node name of a junction, storage unit or outfall node. Cd discharge coefficient of the exchange (default: [2D_OPTIONS] COUPLING_CD, 0.65). Area exchange area, in the mesh's length units squared (sq ft or sq m; default 1.0).

Remarks: The first token is tried as a numeric index first; a number that is not a valid vertex index is looked up as a tag, so purely numeric tags work. An unknown index or tag is a parse error, so this section must follow [2D_VERTICES] in the same file. An unknown node name is fatal when the model initialises.

The exchange is a bidirectional orifice: positive when the surface drains into the node, negative when the node surcharges onto the surface. It opens once the higher of the two heads reaches the node's rim (invert plus maximum depth), so the node's Elevation + MaxDepth should equal the ground elevation at the inlet. The exchange is spread over the cells incident to the vertex, weighted by the water-surface slope.

One row per vertex; a repeated vertex overwrites the earlier row. A Cd or Area token that does not parse as a number is ignored, not reported. An Area that was authored explicitly is never replaced by COUPLING_AREA AUTO.

Naming an outfall couples the outfall's discharge onto the surface and makes the surface stage its dynamic tailwater. See Chapter 9: Two-Dimensional Overland Flow Analysis, section 9.7.

This section has no counterpart in SWMM 5.

Section: [2D_TRIANGLE_NODE_MAP]

Purpose: Couples a mesh cell (triangle or quad) to a node of the one-dimensional network; the whole exchange lands on that cell.

Format:

Cell Node (Cd) (Area)

Parameters: Cell 0-based unified cell index, or the cell's Tag from [2D_TRIANGLES] or [2D_QUADS]. Node name of a junction, storage unit or outfall node. Cd discharge coefficient of the exchange (default: [2D_OPTIONS] COUPLING_CD, 0.65). Area exchange area, in the mesh's length units squared (sq ft or sq m; default 1.0).

Remarks: The first token is tried as a numeric index first and falls back to a tag lookup when the number is not a valid cell index. An unknown index or tag is a parse error, so this section must follow the cell sections in the same file.

Unlike [2D_VERTEX_NODE_MAP], every row appends a coupling: several nodes may couple to one cell. A Cd or Area token that does not parse as a number is ignored.

The exchange law, the rim gate and the outfall behaviour are those of [2D_VERTEX_NODE_MAP]; see Chapter 9: Two-Dimensional Overland Flow Analysis, section 9.7.

This section has no counterpart in SWMM 5.

Section: [2D_NODE_COUPLING]

Purpose: Assigns a node's 1D/2D coupling structure type and optional local parameters. The row is node data and is retained even when no mesh is present; spatial coupling still requires [2D_VERTEX_NODE_MAP] or [2D_TRIANGLE_NODE_MAP].

Format:

Node Type (KEY=VALUE ...)

Parameters: Node name of an existing 1D node; at most one row per node. Type NONE, MANHOLE, GRATE, CURB, OPEN or OUTFALL.

Key	Values / units	Meaning
D	> 0, project length units	Manhole diameter.
PERIMETER	> 0, project length units	Weir crest length.
AREA	> 0, project area units	Orifice/open area.
CHAMBER_AREA	> 0, project area units	1D chamber plan area above the rim.
LID_OPEN_FRACTION	> 0 and <= 1	Open fraction of the lid.
CREST	NODE_RIM / MESH_BED / MAX / MIN	Crest elevation policy; MAX/MIN choose between node rim and mapped mesh bed. Default NODE_RIM.
COEFFS	DEFAULT / RUBINATO2017 / RUBINATO2017_LOWER / RUBINATO2017_UPPER	Local WEIR_ORIFICE coefficient preset.
CW / CSW	> 0	Free/submerged weir coefficients.
COI / COO	> 0	Surface-to-sewer / sewer-to-surface orifice coefficients.
LAW	ORIFICE / WEIR_ORIFICE	Local exchange law, overriding [2D_OPTIONS] COUPLING_LAW.
SPREAD	>= 0, project length units	OUTFALL discharge spread radius.
TAILWATER_RELAX	>= 0, seconds	OUTFALL tailwater relaxation time.

Remarks: NONE accepts no keys and suppresses that node's map rows. OUTFALL accepts only SPREAD and TAILWATER_RELAX; those keys are refused for all other types. An outfall may be OUTFALL or NONE, and OPEN requires a storage node. Unspecified types default to OUTFALL for outfalls, OPEN for storage, MANHOLE for dividers and ordinary junctions, and NONE for inlet or virtual junctions.

All numeric parameters must be finite; duplicate nodes, duplicate keys, unknown keys and invalid type/key combinations are errors. Keys use the single-token KEY=VALUE spelling. WEIR_ORIFICE resolves its geometry and coefficients from these overrides and the global defaults; a legacy map-row Area or Cd retains precedence over the corresponding resolved area or orifice coefficients. These parameters do not turn an unmapped node into a spatial coupling point.

Example:

[2D_NODE_COUPLING]
J1 MANHOLE LAW=WEIR_ORIFICE D=1.2 CREST=NODE_RIM
OUT OUTFALL SPREAD=2 TAILWATER_RELAX=5

Section: [2D_BOUNDARY_CONDITIONS]

Purpose: Assigns a boundary condition to an edge of a cell that lies on the mesh boundary.

Format:

Cell  Edge  WALL
Cell  Edge  NORMAL_FLOW      Slope     (*)  (Group)
Cell  Edge  SPECIFIED_STAGE  Head      (*)  (Group)
Cell  Edge  TS_STAGE         Tseries   (*)  (Group)
Cell  Edge  SPECIFIED_FLOW   Flow      (*)  (Group)
Cell  Edge  TS_FLOW          Tseries   (*)  (Group)
Cell  Edge  RATING_CURVE     Curve     (*)  (Group)

Parameters: Cell 0-based unified cell index (the TRI column of files the engine writes). Edge local edge of that cell: 0 .. 2 for a triangle, 0 .. 3 for a quad (see [2D_TRIANGLES] and [2D_QUADS] for the numbering). Slope bed slope used by the Manning outflow of a NORMAL_FLOW edge (dimensionless). Head fixed water-surface elevation outside a SPECIFIED_STAGE edge, in the mesh's length units (ft or m). Flow fixed discharge per metre of edge for a SPECIFIED_FLOW edge, in the project's flow units per metre; outward positive, so an inflow is negative. Tseries name of a [TIMESERIES] giving the stage (TS_STAGE, project length units) or the per-metre flow (TS_FLOW, project flow units per metre) against time. Curve name of a [CURVES] table giving discharge per metre of edge (project flow units per metre, outward positive) against stage (project length units) for a RATING_CURVE edge.

placeholder for the fifth column, which is reserved and ignored. Group optional label of the edge; stored and written back, never acted on.

Remarks: Every boundary edge not listed is a WALL (zero flux). A row needs at least Cell, Edge and the type; the fourth token may be * or absent to mean "no value". The fourth token must be numeric for NORMAL_FLOW, SPECIFIED_STAGE and SPECIFIED_FLOW and is a name for the others. The sixth token is Group and is read only when a fifth token is present, so write * in the fifth column whenever a Group is given. Edge is checked against the widest cell (0 .. 3) at parse and against the cell's own vertex count at initialise; the Cell index is checked at initialise.

TS_STAGE and SPECIFIED_STAGE share one internal type, as do TS_FLOW and SPECIFIED_FLOW; the TS_ spelling only signals that the parameter is a name. A NORMAL_FLOW edge with a zero slope behaves as a wall (a warning is raised; the slope is never derived from the geometry). Under FULL_SWE a NORMAL_FLOW edge is transmissive.

Series and curve names are resolved once, at the first advance, and evaluated every routing step at the absolute date-time; a name that resolves to nothing is treated as a constant. A constant stage follows the mesh's length unit, including the ;; UNITS: header; a series stage is in the project's display length unit whatever the header says; flows follow FLOW_UNITS (CFS, GPM, MGD, CMS, LPS, MLD). The cumulative volume through each edge, outward positive, enters the 2D mass balance.

The section may also be placed in the external mesh file. See Chapter 9: Two-Dimensional Overland Flow Analysis, section 9.6.

This section has no counterpart in SWMM 5.

Section: [2D_EDGE_CONVEYANCE]

Purpose: Partially or fully blocks an interior edge of the mesh, to represent a leaky berm, a fence or a partly blocked wall between two cells.

Format:

FromVertex ToVertex Conveyance

Parameters: FromVertex 0-based index of one end vertex of the edge. ToVertex 0-based index of the other end vertex; must differ from FromVertex. Conveyance fraction of the edge's flux that passes, in [0, 1]: 0 blocks the edge, 1 leaves it unobstructed.

Remarks: Exactly three tokens. The vertex pair is undirected; a repeated pair takes the last row. A conveyance outside [0, 1] is a parse error; a pair that is not an edge of the mesh is fatal when the model initialises. Edges not listed have a conveyance of 1.

For a feature that must hold water until a true crest elevation, resolve the crest as a line of high vertices and use [2D_OPTIONS] FACE_RECONSTRUCTION VFR_FACE; edge conveyance is the complementary control for partial blockage. The section may also be placed in the external mesh file.

This section has no counterpart in SWMM 5.

Section: [2D_INITIAL_VELOCITY]

Purpose: Gives a non-zero initial velocity to selected cells, for problems whose initial state is not at rest.

Format:

Cell U V

Parameters: Cell 0-based unified cell index (the TRI column of files the engine writes). U initial velocity component along the map x-axis (m/s, always SI). V initial velocity component along the map y-axis (m/s, always SI).

Remarks: Rows may cover any subset of cells; unlisted cells start at rest. The index is checked at parse against the cells already read, so the section must follow [2D_TRIANGLES] and [2D_QUADS] in the same file. At initialise the marcher projects (h u, h v) onto its face normals to seed the face discharges, which a depth-only initial condition cannot represent (the Thacker planar oscillation of the verification suite, for instance). See Chapter 9: Two-Dimensional Overland Flow Analysis, section 9.10.

This section has no counterpart in SWMM 5.

Section: [2D_INFILTRATION_OPTIONS]

Purpose: Sets the update cadence of infiltration on the mesh.

Format:

INFIL_STEP Step

Parameters: Step infiltration update interval as HH:MM:SS, HH:MM or seconds; must be >= 0. 0 (the default) uses the project's WET_STEP.

Remarks: INFIL_STEP is the only keyword accepted; any other is a parse error. [2D_OPTIONS] INFIL_STEP is the canonical spelling of the same value and wins when both are present; the writer emits the key there. The section may also be placed in the external mesh file, where it replaces the inline value.

This section has no counterpart in SWMM 5.

Section: [2D_INFILTRATION_DEFAULTS]

Purpose: Assigns an infiltration method and its parameters to every cell that carries a given tag, or to the whole mesh.

Format:

Tag  NONE
Tag  HORTON               f0  fmin  Decay  DryTime  Fmax  (Dest)
Tag  MODIFIED_HORTON      f0  fmin  Decay  DryTime  Fmax  (Dest)
Tag  GREEN_AMPT           S   Ks    IMD                   (Dest)
Tag  MODIFIED_GREEN_AMPT  S   Ks    IMD                   (Dest)
Tag  CURVE_NUMBER         CN  -     DryTime               (Dest)
Tag  CONSTANT             Rate                            (Dest)

Parameters: Tag a cell tag from [2D_TRIANGLES] or [2D_QUADS], or * for every cell. f0 maximum infiltration rate on the Horton curve (in/hr or mm/hr). fmin minimum infiltration rate on the Horton curve (in/hr or mm/hr). Decay decay rate constant of the Horton curve (1/hr). DryTime time for a fully saturated soil to dry completely (days). Fmax maximum infiltration volume possible (in or mm; 0 if not applicable). S soil capillary suction head (in or mm). Ks soil saturated hydraulic conductivity (in/hr or mm/hr). IMD initial soil moisture deficit (volume of voids / total volume). CN SCS curve number. Rate constant infiltration rate (in/hr or mm/hr). Dest destination of the infiltrated water: LOST (default), SUBCATCH_AQUIFER or AQUIFER_2D.

Remarks: The first token is the tag itself (not the keyword TAG); * is the mesh-wide fallback and may appear on any row. The parameters are positional, in the project's rainfall units, at most five; a - leaves a slot unset (0) and trailing unused columns may be omitted. Dest is recognised as the final token when it is neither numeric nor -. NONE assigns no infiltration to the matching cells. The method spellings are those listed above; the [2D_OPTIONS] INFIL_DEFAULT_METHOD short forms (MOD_HORTON, MOD_GREEN_AMPT, CURVE_NUM) are not accepted on a row.

Precedence at initialise is [2D_INFILTRATION] cell override, then the tag match, then the * row. A row's own Dest overrides [2D_OPTIONS] INFIL_DESTINATION. AQUIFER_2D needs a resolved [2D_AQUIFER]; SUBCATCH_AQUIFER needs the cell to lie inside a subcatchment that has a [GROUNDWATER] aquifer, and is refused when the integrated groundwater kernel is also on (the water would be delivered twice).

The section may also be placed in the external mesh file, where it replaces the inline rows. The formulas are those of the [INFILTRATION] section; the mesh application is in hydrology Chapter 9 (mesh groundwater) and Chapter 9: Two-Dimensional Overland Flow Analysis.

This section has no counterpart in SWMM 5.

Section: [2D_INFILTRATION]

Purpose: Overrides the infiltration method and parameters of a single cell.

Format:

Cell Method (P1 P2 P3 P4 P5) (Dest)

Parameters: Cell 1-based unified cell index (the first triangle is 1; the first quad is the number of triangles + 1). Method NONE, HORTON, MODIFIED_HORTON, GREEN_AMPT, MODIFIED_GREEN_AMPT, CURVE_NUMBER or CONSTANT. P1 .. P5 the method's positional parameters, laid out exactly as in [2D_INFILTRATION_DEFAULTS] (project rainfall units; - = unset). Dest LOST (default), SUBCATCH_AQUIFER or AQUIFER_2D.

Remarks: The bare cell-index columns in [2D_INFILTRATION] and [2D_SNOW] are 1-based. The sections that spell CELL as a scope keyword ([2D_INITIAL_QUALITY], [2D_INITIAL_BED_QUALITY], [2D_AQUIFER], the quality and [GW_*] sections) are 1-based as well, whereas the TRI columns of [2D_INITIAL_VELOCITY], [2D_BOUNDARY_CONDITIONS] and [2D_BOUNDARY_QUALITY] are 0-based. Only the lower bound is checked at parse; a cell beyond the mesh is reported at initialise. A cell row wins over any tag or * row of [2D_INFILTRATION_DEFAULTS].

The section may also be placed in the external mesh file, where it replaces the inline rows.

This section has no counterpart in SWMM 5.

Section: [2D_SNOW_OPTIONS]

Purpose: Controls mesh snow processing and its update interval independently of subcatchment snow.

Formats:

SNOWMELT AUTO / YES / NO

SNOW_STEP DEFAULT / Step

Key	Default	Meaning
SNOWMELT	AUTO	AUTO processes assigned cells; NO retains authored assignments without running mesh snow. YES requires an assignment and at least one active cell with a weather footprint at initialization.
SNOW_STEP	DEFAULT	Inherits [TEMPERATURE] SNOW_STEP. An explicit interval uses seconds or HH:MM[:SS] and must be from 1 to 21600 seconds. DEFAULT restores inheritance.

Remarks: [OPTIONS] IGNORE_SNOWMELT YES disables both subcatchment and mesh snow, including when mesh SNOWMELT is YES. Selecting YES does not assign a snowpack. Assign cells through [2D_SNOW_DEFAULTS] or [2D_SNOW]; cells with no resolved pack pass precipitation through without mesh snow processing.

When degree-day mesh snow and 2D ground conduction are both active, the soil column retains its configured top boundary independently of degree-day melt. AIR, FIXED, TIMESERIES, HEAT_FLUX and FLUX_TIMESERIES are soil-side external energy terms; SURFACE_WATER keeps its existing surface-water/soil coupling. Degree-day snow has no energy state, so no combined snow/soil energy closure is reported. For assigned UEB cells with an active 2D ground column, modeled contact replaces the pack's prescribed QG over the accepted snow-covered contact area. The contact uses UEB surface temperature and the soil top half-layer plus authored surface resistance; accepted soil joules are applied with the opposite sign to the UEB energy ledger. Cells or area without a modeled UEB contact keep their configured external soil boundary.

This section requires a build with 2D support and has no counterpart in SWMM 5.

Section: [2D_SNOW_DEFAULTS]

Purpose: Assigns a named snowpack to the whole mesh or to cells carrying a specific tag.

Formats:

*          SNOWPACK Name (Key Value ...)
Tag        SNOWPACK Name (Key Value ...)
TAG Tag    SNOWPACK Name (Key Value ...)

Parameters: Tag exact cell tag from [2D_TRIANGLES] or [2D_QUADS]; * is the mesh-wide fallback. The TAG prefix is optional; quote tags or names containing spaces. Name named pack from [SNOWPACKS], or NONE to disable snow for this scope.

Override key	Units and accepted range	When omitted
FC	Forest-cover fraction, 0 to 1	Inherit from the named pack or a broader mesh row.
F	Nonnegative precipitation drift multiplier	Inherit from the named pack or a broader mesh row.
QG	Ground heat flux in W/m², either sign	Inherit from the named pack or a broader mesh row.
AEP	Positive extinction depth in m	Inherit from the named pack or a broader mesh row.
SLOPE	Degrees, at least 0 and less than 90	Use cell geometry, unless supplied by a broader mesh row.
ASPECT	Degrees, 0 to 360	Use cell geometry, unless supplied by a broader mesh row.

Remarks: Override units are fixed in both US and SI projects. Keys on a row must be unique and values finite. Supply SLOPE and ASPECT together, or omit both. A row's pack replaces the broader assignment; explicitly supplied override fields replace broader fields, while omitted fields retain them. Resolution applies the * row first, then the exact tag, then the cell row in [2D_SNOW]. A later authored row with the same tag replaces that tag's entire earlier row. NONE disables snow even when a broader row assigned a pack.

Example:

[2D_SNOW_DEFAULTS]
* SNOWPACK SP
TAG Forest SNOWPACK SP FC 0.6
TAG Road SNOWPACK NONE

This section requires a build with 2D support and has no counterpart in SWMM 5.

Section: [2D_SNOW]

Purpose: Overrides the snowpack assignment and optional site fields of an individual mesh cell.

Formats:

Cell SNOWPACK Name (Key Value ...)

CELL Cell SNOWPACK Name (Key Value ...)

Parameters: Cell positive, one-based index in the combined triangle/quad cell ordering. The CELL prefix is optional. Cells beyond the loaded mesh are refused at initialization when mesh snow is enabled. Name named pack from [SNOWPACKS], or NONE to disable this cell's snow processing.

Remarks: The FC, F, QG, AEP, SLOPE and ASPECT keys and inheritance rules are those of [2D_SNOW_DEFAULTS]. A cell row has highest priority; SLOPE and ASPECT must be supplied together. A later row for the same cell replaces its entire earlier row. Input-file indices are one-based; Python and C API snapshot indices are zero-based.

Example:

[2D_SNOW]
CELL 1 SNOWPACK SP SLOPE 15 ASPECT 180
CELL 2 SNOWPACK NONE

Each assigned cell keeps its own snow water, energy, thermal history and accepted ledger. It shares the named pack's parameters with subcatchments, not their snow state. The pack's resolved model may be DEGREE_DAY or UEB; energy-balance fields unavailable for degree-day cells are reported as NaN. Liquid released by snow becomes surface input rather than being counted as a second precipitation source.

This section requires a build with 2D support and has no counterpart in SWMM 5.

Section: [2D_SURFACE_OWNERSHIP]

Purpose: Experimental Stores opt-in surface ownership records for review of subcatchment and LID footprints over the mesh. This release supports authoring and geometric review; the runtime water, quality and ET adapter is not yet qualified.

Format:

Subcatchment SUBCATCH UNIFORM

Parameters: Subcatchment name of an existing subcatchment to include in the ownership review. SUBCATCH the only supported representation token. UNIFORM the only supported distribution token.

Remarks: Each row has exactly three tokens. Duplicate subcatchment records are rejected. Review requires active routing and an enabled 2D aquifer in MODE MESH; ownership records alone do not enable or create an aquifer. The resolver checks source geometry and area, overlap and connected source shares before accepting a replacement. INP and GeoPackage preserve the optional records.

Initialization currently refuses any stored ownership record with an error explaining that the completed-interval adapter is not qualified. Remove the records to run the existing formulation. Absence of this section retains the existing runoff, groundwater and weather accounting.

Section: [2D_AQUIFER_OPTIONS]

Purpose: Sets the global options of the integrated two-zone groundwater kernel that runs beneath the mesh.

Format:

Keyword Value

Parameters:

Keyword	Values	Default	Description
SOIL_CHAR	RUSSO / GARDNER / BROOKS_COREY / VAN_GENUCHTEN	RUSSO	Soil-characteristic law shaping conductivity and water content against pressure head, for rows that do not set their own.
CLOSURE	AUTO / CLOSED_FORM / ENSLAVED / SIGMA	AUTO	Unsaturated-zone closure: a bulk store with a quasi-steady recharge (CLOSED_FORM), that store made algebraic in the water table (ENSLAVED), or an explicit column of sigma layers (SIGMA). AUTO selects per cell at initialise.
M_LAYERS	2 .. 128	8	Number of sigma layers of a SIGMA column, for rows that do not set their own.
CAPILLARY_DIFF	YES / TRUE / 1 / NO / FALSE / 0	NO	Optional diffusive term of the SIGMA column.
C_GW	(0, 1]	0.5	Stability safety factor of the saturated-zone step.
C_COL	(0, 1]	0.9	Stability safety factor of the unsaturated column step.
FORCE_CLOSED_FORM	YES / TRUE / 1 / NO / FALSE / 0	NO	Suppress the automatic switch away from CLOSED_FORM on strongly capillary soils.
MODE	MESH / PER_SUBCATCH	MESH	MESH runs one aquifer cell under every mesh cell. PER_SUBCATCH runs one degenerate cell per subcatchment with no lateral flow, exchanging with the outlet node.
DUNNE	YES / TRUE / 1 / NO / FALSE / 0	YES	Saturation-excess transfer from the aquifer to the surface cell above it. Exists for comparison runs; NO breaks the mass balance between the two domains.
GW_ET	NONE / CAPILLARY_RISE / BOUNDARY_ET / BOTH	NONE	Subsurface evapotranspiration: capillary rise from the water table, removal at the top of the unsaturated column, both, or neither.
LINK_SEEPAGE	AUTO / NONE / TWO_WAY	AUTO	AUTO delivers conduit seepage to the aquifer cells crossed by the conduit, weighted by the length in each cell. NONE leaves seepage as a system loss. TWO_WAY uses a signed conductance law, allowing a conduit below the water table to gain water. Per-conduit overrides are set in [2D_AQUIFER_LINKS].

Remarks: Authoring any [2D_AQUIFER_OPTIONS], [2D_AQUIFER], [2D_AQUIFER_NODE] or [2D_AQUIFER_LINKS] row turns the kernel on unless [2D_OPTIONS] GROUNDWATER NO is set. A value of GW_ET spelled in [2D_OPTIONS] is folded into this section when the model opens. The writer emits only the keys that differ from their defaults.

The kernel is described in hydrology Chapter 9 (mesh groundwater).

This section has no counterpart in SWMM 5.

Section: [2D_AQUIFER]

Purpose: Gives the soil properties of the aquifer beneath the whole mesh, beneath every cell carrying a tag, or beneath one cell.

Format:

*         Ks  Zs  ThetaS  ThetaR  Alpha  (Key value) ...
TAG name  Ks  Zs  ThetaS  ThetaR  Alpha  (Key value) ...
CELL n    Ks  Zs  ThetaS  ThetaR  Alpha  (Key value) ...

Parameters: name a cell tag from [2D_TRIANGLES] or [2D_QUADS]. n 1-based unified cell index. Ks saturated hydraulic conductivity (in/hr or mm/hr); > 0. Zs thickness of the soil column from the aquifer bottom to the surface (ft or m); > 0. ThetaS porosity, i.e. saturated water content (fraction); in (0, 1]. ThetaR residual water content (fraction); in [0, ThetaS). Alpha sorptive number of the Gardner and Russo laws (1/ft or 1/m); > 0.

Keyword pairs, in any order after the five positional columns:

Keyword	Value	Default	Description
PSI_B	>= 0 (ft or m)	0.20	Air-entry pressure head of the Brooks-Corey law.
LAMBDA	> 0	0.40	Pore-size distribution index of the Brooks-Corey law.
N	> 1	1.6	Shape parameter n of the van Genuchten law (m = 1 - 1/n).
L	number	0.5	Mualem tortuosity exponent of the van Genuchten law.
C_LOSS	>= 0 (in/hr or mm/hr)	0	Deep-loss coefficient: the percolation rate out of the aquifer bottom at full saturation, scaled by the saturated fraction of the column.
HG0	>= 0 (ft or m)	unset	Initial saturated thickness above the aquifer bottom, clamped to Zs. Unset leaves the water table at the aquifer bottom.
SOIL_CHAR	RUSSO / GARDNER / BROOKS_COREY / VAN_GENUCHTEN	from [2D_AQUIFER_OPTIONS]	Soil-characteristic law of these cells.
CLOSURE	AUTO / CLOSED_FORM / ENSLAVED / SIGMA	from [2D_AQUIFER_OPTIONS]	Unsaturated closure of these cells.
M_LAYERS	2 .. 128	from [2D_AQUIFER_OPTIONS]	Sigma layers of these cells' columns.

Remarks: Rows are resolved in the order *, then TAG, then CELL, each pass overwriting the previous, so the most specific scope wins. All five positional columns are required. Values are authored in the project's units and converted to SI once at initialise; the writer emits the rows as authored, so a load-and-save is byte-identical. A CELL index beyond the mesh is reported at initialise.

The theory of the two zones, the soil laws and the closures is in hydrology Chapter 9 (mesh groundwater).

This section has no counterpart in SWMM 5.

Section: [2D_AQUIFER_NODE]

Purpose: Couples a node of the one-dimensional network to the aquifer cell beneath it, optionally through a semi-confining bed layer.

Format:

Node Cell (KC k) (DC d) (AREA a)

Parameters: Node name of a node. Cell 1-based unified index of the mesh cell containing the node. k hydraulic conductivity of the bed layer (in/hr or mm/hr); >= 0. 0 (default) means a direct Darcy exchange with no bed. d thickness of the bed layer (ft or m); >= 0; must be > 0 whenever k > 0. a exchange area (sq ft or sq m); >= 0. 0 (default) uses the cell's own area.

Remarks: The three keyword pairs may appear in any order and any may be omitted. Each node may have one row only; a second row for the same node is an error at initialise, as is an unknown node or a cell beyond the mesh. Values are in the project's units and converted at initialise.

The exchange law is described in hydrology Chapter 9 (mesh groundwater).

This section has no counterpart in SWMM 5.

Section: [2D_AQUIFER_LINKS]

Purpose: Overrides exchange between an individual conduit and the integrated aquifer beneath the mesh.

Format:

Link (KC k) (DC d) (EXCHANGE YES|NO)

Parameters:

Parameter	Values	Default	Description
Link	conduit name	required	Conduit whose exchange settings are overridden.
KC	finite number >= 0 (in/hr or mm/hr)	0	Bed hydraulic conductivity for TWO_WAY exchange. Zero or omission uses the conduit's [LOSSES] seepage rate.
DC	finite number >= 0 (ft or m)	0	Bed thickness for TWO_WAY exchange. Zero or omission uses the conduit's full depth.
EXCHANGE	YES / TRUE / 1 / NO / FALSE / 0	YES	NO excludes this conduit from aquifer exchange; its ordinary 1D seepage remains a system loss.

Remarks: The keyword pairs are optional and may appear in any order. Unknown keywords, missing values, non-finite numbers and negative KC or DC values are parse errors. An unknown link or a link that is not a conduit produces a warning when exchange links are resolved, and its row is ignored. If several rows name the same conduit, the first matching row supplies its settings.

Set LINK_SEEPAGE TWO_WAY in [2D_AQUIFER_OPTIONS] to use KC and DC. A positive KC can enable exchange for a conduit with no [LOSSES] seepage rate. With the default LINK_SEEPAGE AUTO, the existing seepage rate supplies one-way recharge and KC and DC do not change that rate. LINK_SEEPAGE NONE disables conduit-to-aquifer exchange globally.

The engine locates the conduit from its endpoints in [COORDINATES] and any [VERTICES], and assigns exchange to the mesh cells crossed by that polyline. The aquifer must be active and the conduit must overlap the mesh. The writer retains the authored KC and DC values and writes non-default settings.

Example:

[2D_AQUIFER_OPTIONS]
LINK_SEEPAGE TWO_WAY
 
[2D_AQUIFER_LINKS]
;;Link  Options
C1      KC 50 DC 2.5
C2      EXCHANGE NO

This section has no counterpart in SWMM 5.

Section: [2D_AQUIFER_BOUNDARIES]

Purpose: Prescribes hydraulic forcing at exterior edges of the integrated mesh aquifer. An unspecified edge is no-flow. These boundaries require MODE MESH in [2D_AQUIFER_OPTIONS] and an active aquifer covering the boundary cell.

Format:

CELL Cell EDGE Edge HEAD CONST Head
CELL Cell EDGE Edge HEAD SERIES Tseries
CELL Cell EDGE Edge FLOW CONST Flow
CELL Cell EDGE Edge FLOW SERIES Tseries

Parameters: Cell 1-based unified mesh cell index. Edge 0-based local edge: 0 .. 2 for triangles, 0 .. 3 for quads. Head prescribed groundwater head elevation, in project length units. Flow total discharge across the edge, in cubic metres per second, positive inward; always SI, including in US-unit projects. Tseries a [TIMESERIES] supplying head or flow in the same units as its constant counterpart.

Remarks: Each row has exactly seven tokens. Constants must be finite. Duplicate hydraulic edges, interior edges, out-of-range cell/edge indices and cells without active aquifer coverage are refused. Local edge e joins vertices (e+1) modulo the cell's vertex count and (e+2) modulo that count.

HEAD and time-varying FLOW may reverse. Whenever inflow is possible, every enabled groundwater species needs an explicit concentration in [GW_BOUNDARY_QUALITY], including zero. Extraction uses interior donor composition. Quality rows need a matching hydraulic boundary; a quality row alone supplies no water. A concentration and one independent imposed mass/heat flux may coexist for each edge/species. FLOW is a total edge rate, unlike the per-length imposed species fluxes in [GW_BOUNDARY_QUALITY].

Section: [2D_INITIAL_QUALITY]

Purpose: Sets the initial concentration of a transported species in the water standing on the mesh at the start of the simulation.

Format:

*          Species  Conc
TAG name   Species  Conc
CELL n     Species  Conc

Parameters: name a cell tag from [2D_TRIANGLES] or [2D_QUADS]. n 1-based unified cell index. Species name of a pollutant, of a species of the reactions component, or __WATER_AGE__ or __TEMPERATURE__ when that transport is on. Conc initial value: concentration in the species' units, water age in hours, temperature in degrees C. Must be finite and >= 0.

Remarks: A * row has exactly three tokens and a TAG or CELL row exactly four. Rows are applied in the order *, then TAG, then CELL, later writes winning. The seeded mass is the concentration times the cell's initial volume, so a dry cell receives nothing. An unknown species, a tag that matches no cell, a cell beyond the mesh, or rows in a model that carries no transported species are fatal at initialise.

The section may also be placed in the external mesh file. The surface transport scheme is in Chapter 9: Two-Dimensional Overland Flow Analysis.

This section has no counterpart in SWMM 5.

Section: [2D_INITIAL_BED_QUALITY]

Purpose: Sets initial pollutant or water-age concentration in the finite porewater of a local 2D mesh bed.

Format:

*          Species  Conc
TAG name   Species  Conc
CELL n     Species  Conc

Parameters: name a cell tag from [2D_TRIANGLES] or [2D_QUADS]. n 1-based unified cell index. Species name of a carried pollutant or reaction species, or __WATER_AGE__ when water age is on. __TEMPERATURE__ is not a bed species; bed temperature is initialized by the heat model. Conc concentration in the species' units, or water age in hours. Must be finite and >= 0.

Remarks: The same *, then TAG, then CELL precedence applies as in [2D_INITIAL_QUALITY]. The seeded mass is concentration × local-bed pore volume (cell area × bed thickness × porosity), and the seed is saved as the bed's initial mass for exchange accounting. This section requires HEAT_MODEL COUPLED and BED_HEAT_MODEL LOCAL_STORAGE. Groundwater-owned GROUND_COLUMN porewater is initialized through [GW_INITIAL_QUALITY]. Unknown species, unmatched tags, out-of-range cells or an inactive local bed are fatal at initialise.

The section may also be placed in the external mesh file. The mesh bed and hyporheic formulation is in Chapter 9: Two-Dimensional Overland Flow Analysis.

This section has no counterpart in SWMM 5.

Section: [2D_BOUNDARY_QUALITY]

Purpose: Sets the concentration of a species carried by the water that enters the mesh through a non-wall boundary edge.

Format:

Cell Edge Species Conc

Parameters: Cell 0-based unified cell index (the TRI column of files the engine writes). Edge local edge of that cell (0 .. 2 for a triangle, 0 .. 3 for a quad), one that carries a [2D_BOUNDARY_CONDITIONS] row. Species name of a pollutant, of a species of the reactions component, or __WATER_AGE__ or __TEMPERATURE__. Conc inflow value: concentration in the species' units, water age in hours, temperature in degrees C. Must be finite and >= 0.

Remarks: Exactly four tokens. The value applies whenever the edge's boundary condition brings water in; outflow carries the cell's own concentration. A cell beyond the mesh, an unknown species, or rows in a model that carries no transported species are fatal at initialise.

The section may also be placed in the external mesh file.

This section has no counterpart in SWMM 5.

Section: [2D_COVERAGES]

Purpose: Assigns land uses, and the percentage of area each covers, to the cells of the mesh, so that pollutant buildup, washoff and street sweeping run on the overland surface as they do on subcatchments.

Format:

*          LandUse  Percent  (LandUse  Percent) ...
TAG name   LandUse  Percent  (LandUse  Percent) ...
CELL n     LandUse  Percent  (LandUse  Percent) ...

Parameters: name a cell tag from [2D_TRIANGLES] or [2D_QUADS]. n 1-based unified cell index. LandUse name of a land use from the [LANDUSES] section. Percent percent of the cell's area covered by that land use; >= 0, and the percents of one row sum to at most 100.

Remarks: A row carries the whole coverage set of its scope: a later row with the same scope replaces the earlier one rather than adding to it, and the scopes resolve *, then TAG, then CELL, the most specific winning. An unknown land use, a tag that matches no cell or a cell beyond the mesh is fatal at initialise, as is a model with no [LANDUSES] or no transported species.

Buildup accrues per cell, land use and species with the land use's [BUILDUP] function, is swept on the [LANDUSES] schedule and washed off by the cell's own runoff (its net outflow per runoff step) into the cell's species row. Under [2D_OPTIONS] RAINFALL_MODE NONE the rows are inert (the subcatchments own the surface); a covered cell that lies inside a subcatchment which itself has [COVERAGES] raises a double-counting warning. A land use whose buildup is normalised per curb length needs a [2D_CURB_LENGTH] on every cell it covers.

This section has no counterpart in SWMM 5.

Section: [2D_LOADINGS]

Purpose: Sets the initial pollutant buildup on the cells of the mesh at the start of the simulation.

Format:

*          Species  Buildup
TAG name   Species  Buildup
CELL n     Species  Buildup

Parameters: name a cell tag from [2D_TRIANGLES] or [2D_QUADS]. n 1-based unified cell index. Species name of a pollutant or of a species of the reactions component (water age and temperature do not build up). Buildup initial buildup per unit land area (lbs/acre or kg/ha); >= 0.

Remarks: Exactly one species and value after the scope. Scopes resolve *, then TAG, then CELL. The value is divided among the cell's covered land uses; for a land use normalised per curb length it is converted with the cell's [2D_CURB_LENGTH]. Cells without a row start with the buildup their [BUILDUP] functions reach after [OPTIONS] DRY_DAYS, as subcatchments do. Rows without any [2D_COVERAGES] raise a warning and build up nothing.

This section has no counterpart in SWMM 5.

Section: [2D_CURB_LENGTH]

Purpose: Gives the length of curb on a mesh cell, for land uses whose pollutant buildup is normalised per unit curb length.

Format:

*          Length
TAG name   Length
CELL n     Length

Parameters: name a cell tag from [2D_TRIANGLES] or [2D_QUADS]. n 1-based unified cell index. Length curb length on the cell (ft or m); >= 0.

Remarks: Exactly one value after the scope. Scopes resolve *, then TAG, then CELL. A cell covered by a land use with a per-curb buildup function and no positive curb length is an error at initialise.

This section has no counterpart in SWMM 5.

Section: [GW_TRANSPORT_OPTIONS]

Purpose: Experimental Sets active bulk-groundwater transport switches and stores additional thermal configuration. The class switches and DISPERSION control the running kernel; the presence of a parsed thermal key does not establish an implemented conduction or thermal-boundary solver.

Format:

TRANSPORT_POLLUTANTS   YES / NO
TRANSPORT_MSX          YES / NO
TRANSPORT_AGE          YES / NO
TRANSPORT_TEMPERATURE  YES / NO
DISPERSION             YES / NO
CONDUCTION             YES / NO
SURFACE_THERMAL_BC     AIR
SURFACE_THERMAL_BC     SURFACE_WATER
SURFACE_THERMAL_BC     FIXED  Temp
SURFACE_THERMAL_BC     HEAT_FLUX  Flux
SURFACE_THERMAL_BC     TIMESERIES  Tseries
SURFACE_THERMAL_BC     FLUX_TIMESERIES  Tseries
DEEP_THERMAL_BC        GEOTHERMAL_FLUX  Flux   (DEPTH z)
DEEP_THERMAL_BC        FIXED_TEMP       Temp   (DEPTH z)
DEEP_THERMAL_BC        TIMESERIES       Tseries  (DEPTH z)
THERMAL_MIXING         ARITHMETIC / GEOMETRIC
C_DIFF                 value

Parameters:

Keyword	Values	Default	Description
TRANSPORT_POLLUTANTS	YES / ON / NO / OFF	YES	Carry the [POLLUTANTS] species in the aquifer.
TRANSPORT_MSX	YES / ON / NO / OFF	YES	Carry the reactions component's species in the aquifer.
TRANSPORT_AGE	YES / ON / NO / OFF	YES	Carry water age in the aquifer.
TRANSPORT_TEMPERATURE	YES / ON / NO / OFF	YES	Carry temperature in the aquifer.
DISPERSION	YES / ON / NO / OFF	YES	Activate the dispersivities and molecular diffusivity of [GW_TRANSPORT_PARAMS].
CONDUCTION	YES / ON / NO / OFF	YES	Activate vertical and lateral heat conduction.
SURFACE_THERMAL_BC	AIR / SURFACE_WATER / FIXED Temp / HEAT_FLUX Flux / TIMESERIES Tseries / FLUX_TIMESERIES Tseries	AIR	Top condition when the column is not inundated: air or surface-water temperature, a fixed value (degrees C), a heat flux (W/m²), or a temperature/flux [TIMESERIES].
DEEP_THERMAL_BC	GEOTHERMAL_FLUX Flux / FIXED_TEMP Temp / TIMESERIES Tseries, each optionally followed by DEPTH z	GEOTHERMAL_FLUX	Condition at the bottom of the column: a geothermal heat flux (W per sq m), a fixed temperature (degrees C) or a [TIMESERIES]; DEPTH z (>= 0, metres) places it.
THERMAL_MIXING	ARITHMETIC / GEOMETRIC	ARITHMETIC	How the effective thermal conductivity of the soil-water mixture is averaged.
C_DIFF	(0, 1]	0.4	Explicit diffusion Courant number bounding the transport step.

Remarks: FIXED and FIXED_TEMP require a number and GEOTHERMAL_FLUX a number; TIMESERIES requires a series name. DEPTH is read only as the fourth and fifth tokens of a DEEP_THERMAL_BC line. Naming a [GW_*] section preserves its authored configuration for the writer; active support depends on the specific option and aquifer kernel.

When [OPTIONS] HEAT_TRANSPORT, [2D_OPTIONS] GROUNDWATER and the porous-equilibrium thermal model are active, CONDUCTION controls heat transfer within the thermal columns and supported boundaries are applied by the selected thermal owner. A parsed key alone does not establish activation: check the parent process, transport temperature state, model selection and surface coupling options. Active named forcing is documented under [GW_SOURCES].

The intended formulation is described in hydrology Chapter 9 (mesh groundwater).

This section has no counterpart in SWMM 5.

Section: [GW_TRANSPORT_PARAMS]

Purpose: Experimental Gives scoped solute and thermal properties. The active bulk kernel resolves grain density, dispersivities and molecular diffusivity; the additional thermal and vapour fields are retained without implying an operational thermal solver.

Format:

*          (RhoS  Cs  LambdaS  As  AlphaL  AlphaT  Dm  Dv  GeoFlux)
TAG name   (RhoS  Cs  LambdaS  As  AlphaL  AlphaT  Dm  Dv  GeoFlux)
CELL n     (RhoS  Cs  LambdaS  As  AlphaL  AlphaT  Dm  Dv  GeoFlux)

Parameters: name a cell tag from [2D_TRIANGLES] or [2D_QUADS]. n 1-based unified cell index. RhoS grain density (kg per cu m; default 2650). Cs grain specific heat (J per kg per K; default 880). LambdaS grain thermal conductivity (W per m per K; default 2.0). As specific surface area of the grains (sq m per kg; default 0). AlphaL longitudinal dispersivity (m; default 1.0). AlphaT transverse dispersivity (m; default 0.1). Dm molecular diffusivity (sq m per s; default 1.0e-9). Dv vapour diffusivity (sq m per s; default 1.0e-9). GeoFlux geothermal flux (W per sq m), or the deep temperature (degrees C) when DEEP_THERMAL_BC is FIXED_TEMP; default 0.065. The only signed column.

Remarks: All nine columns are positional and optional; an omitted column or a - keeps the default. More than nine columns is a parse error, and every column but GeoFlux must be >= 0. Values are SI. Scopes resolve *, then TAG, then CELL by order of the rows; a tag that matches no cell or a cell beyond the mesh is reported when the model initialises.

The running bulk kernel uses grain density for sorption retardation and longitudinal dispersivity/molecular diffusivity for dispersion. Retaining the remaining columns does not implement the fuller thermal or vapour formulation.

This section has no counterpart in SWMM 5.

Section: [GW_SORPTION]

Purpose: Implemented Gives the linear sorption partition coefficient and optional first-order decay of an enabled bulk aquifer species, by scope.

Format:

*          Species  Kd  (Decay)
TAG name   Species  Kd  (Decay)
CELL n     Species  Kd  (Decay)

Parameters: name a cell tag from [2D_TRIANGLES] or [2D_QUADS]. n 1-based unified cell index. Species name of a pollutant, of a species of the reactions component, or __WATER_AGE__ or __TEMPERATURE__. Kd linear partition coefficient (L per kg); >= 0. Decay first-order decay rate (1/day); >= 0. Absent or -: a pollutant uses its [POLLUTANTS] decay coefficient.

Remarks: Scopes resolve *, then TAG, then CELL. An unknown species, a tag that matches no cell or a cell beyond the mesh is reported when the model initialises.

The active bulk kernel applies linear sorption to the dissolved mobile fraction and first-order decay to solute stores. Reserved age and temperature rows are not sorbed or decayed by these coefficients.

This section has no counterpart in SWMM 5.

Section: [GW_INITIAL_QUALITY]

Purpose: Implemented Seeds SAT and UNSAT concentration, water age or temperature in the active aquifer. LAYER is retained for authoring but is not operational.

Format:

*          SAT        Species  Value
*          UNSAT      Species  Value
*          LAYER j    Species  Value
TAG name   Zone       Species  Value
CELL n     Zone       Species  Value
FILE  Fname

Parameters: name a cell tag from [2D_TRIANGLES] or [2D_QUADS]. n 1-based unified cell index. Zone SAT (the saturated zone), UNSAT (the unsaturated zone) or LAYER j (layer j of a SIGMA column, j >= 1). Species name of a pollutant, of a species of the reactions component, or __WATER_AGE__ or __TEMPERATURE__. Value initial value: concentration in the species' units, water age in seconds, temperature in degrees C. Concentrations must be >= 0; age and temperature may be negative. Fname name of a CSV file holding the same tokens per line (scope, zone, species, value).

Remarks: The FILE form names a sidecar resolved relative to the input file's directory and read when the model initialises. Its fields may be separated by commas, semicolons, tabs or spaces, and a first line that does not parse is taken as a header. A missing file is reported at initialise, as is an unknown species, a tag that matches no cell, a cell beyond the mesh, or a negative concentration.

Active bulk groundwater rejects LAYER rows with an initialization error; they never alias UNSAT. Initial values resolve in GLOBAL, TAG, then CELL precedence, independent of row order.

This section has no counterpart in SWMM 5.

Section: [GW_BOUNDARY_QUALITY]

Purpose: Planned Declares quality on a groundwater boundary edge. Authoring and round-trip persistence are supported, but a hydraulic edge binding is not yet available.

Format:

Cell  Edge  Species  CONC      Value
Cell  Edge  Species  TS        Tseries
Cell  Edge  Species  MASSFLUX  Value
Cell  Edge  Species  HEATFLUX  Value

Parameters: Cell 1-based unified cell index. Edge local edge of that cell, 0-based (0 .. 2 for a triangle, 0 .. 3 for a quad). Species name of a pollutant, of a species of the reactions component, or __WATER_AGE__ or __TEMPERATURE__. CONC the value is a concentration in the species' units (temperature in degrees C). TS the value is the name of a [TIMESERIES] of that quantity. MASSFLUX the value is a mass flux per metre of edge. HEATFLUX the value is a heat flux per metre of edge. Value a number, or the name of a [TIMESERIES] in its place. Tseries name of a [TIMESERIES].

Remarks: Exactly five tokens. For CONC, MASSFLUX and HEATFLUX a non-numeric fifth token is taken as a series name. The edge is checked against the cell's own vertex count at initialise, as are the cell index, the species name and any series name.

Active groundwater refuses these records at initialization with an actionable unsupported-boundary diagnostic. Use an operational named source where that represents the intended physical forcing; an edge flux is not automatically converted to a source.

This section has no counterpart in SWMM 5.

Section: [GW_SOURCES]

Purpose: Implemented Applies named wells and sources or sinks to the active aquifer, with independent injected species terms and cumulative water and species budgets.

Format:

Name  *        FLOW  Flow  [SCALE Factor]  [Species CONC|MASS Value] ...
Name  CELL n   FLOW  Flow  [SCALE Factor]  [Species CONC|MASS Value] ...
Name  TAG tag  FLOW  Flow  [SCALE Factor]  [Species CONC|MASS Value] ...
Name  XY x y   FLOW  Flow  [SCALE Factor]  [Species CONC|MASS Value] ...

Parameters: Name unique source name. n 1-based unified cell index (the C API uses zero-based indices). tag a tag from [2D_TRIANGLES] or [2D_QUADS]. x, y source coordinates; the existing XY locator chooses the nearest cell centroid. Flow total cubic metres per second, positive for injection and negative for extraction, or a [TIMESERIES] name. GLOBAL (*) and TAG totals are area-weighted across matching active aquifer cells; CELL applies to one cell. Factor finite nonnegative multiplier, default one; scales FLOW and MASS, never CONC itself. Species enabled groundwater pollutant or reaction species, __WATER_AGE__, or __TEMPERATURE__. CONC native injected concentration (age in seconds and temperature in degrees C). Only temperature concentration can be negative. Extraction carries existing dissolved aquifer quality. MASS independent pollutant loading in mg/s for MG/L, ug/s for UG/L, or count/s for #/L. MASS for unresolved reaction-species units, age, or temperature is refused. MASS is nonnegative and can operate with zero FLOW. Value finite constant or [TIMESERIES] name.

Remarks: Series interpolate linearly and hold their endpoints outside the recorded range. Their absolute times are anchored to the complete model start datetime, including a non-midnight start. Flow times concentration is integrated over common linear intervals. Flow sign reversals are applied chronologically; extraction is limited by drainable water available at that interval, and its ledger records actual rather than requested delivery. Existing cross-cadence water and species transfers are apportioned by interval duration. This remains a numerically split groundwater scheme, not a claim of timestep-independent concentrations.

Duplicate source names, duplicate species terms within a source, empty matched scopes, disabled or unknown species, unreadable or non-monotonic series, and invalid values produce diagnostics rather than successful inert forcing. Reactive/thermal groundwater forcing requires reconstruction order one. The standalone CPU passive pollutant/age CLOSED_FORM/ENSLAVED/SIGMA RK2 profile accepts authored wells and hydraulic HEAD/FLOW edges; reactions, heat and borrowed owners remain guarded (Hydrology §9.11).

Source injection/extraction and species inflow/outflow append separate public API, report, and HDF5 ledger terms without renumbering historical terms. HDF5 groundwater water/species ledger axes now have 14/15 terms, identified by their terms metadata. Native hotstarts carrying source species ledgers use version 7; new readers continue reading versions 1–6, including the original eleven-term version 6 species ledger. Version 7 is not readable by older engines.

This section has no counterpart in SWMM 5.

2.5 Process Component Configuration Sections

The sections in this part of the chapter are not read by the input parser's section registry. Each belongs to a process component — a reaction system, the Eulerian transport engine, the heat module or the water-age tracker — and is read by that component from the file named in its [PROCESS_COMPONENTS] row (Section: [PROCESS_COMPONENTS]):

[PROCESS_COMPONENTS]
org.hydrocouple.openswmm.reactions       config="model.rxn"
org.hydrocouple.openswmm.transport.ard   config="model.ard"
org.hydrocouple.openswmm.waterage        config="model.age"
org.hydrocouple.openswmm.heat            config="model.heat"

Dispatch. Every row is Id key="value" .... The first token is the component id; every further token must be a key="value" pair (the quotes are optional and are stripped), and one that is not is a parse error naming the component and the token. The key CONFIG (case-insensitive) names the component's configuration file; any other key is passed to the component unchanged. At open, after the whole .inp has been read, the engine resolves the rows in file order: an id that appears twice is refused; an id that looks like a shared-library path (contains a path separator or ends in .so, .dylib or .dll) is refused until HydroCouple library loading arrives (plan phase HC2); an unknown id is refused with the list of known ids; a known id whose implementation has not landed is refused with the plan phase that delivers it; a row without CONFIG is refused. Otherwise the file is read — a relative path resolves against the directory of the .inp — and handed to the component, which parses its own sections and reports every error it finds. Errors from any component fail the open unless the engine was opened leniently, in which case they are recorded and the configuration that failed is discarded wholesale (no component ever half-applies).

File dialect. A component file uses the bracketed-section dialect of the .inp: [SECTION] headers (case-insensitive), ; comments, blank lines ignored, one record per line. Content before the first header is an error, and a component file may not itself contain a [PROCESS_COMPONENTS] section (no recursion). The conventional extensions are .rxn (reactions), .ard (Eulerian transport), .age (water age) and .heat (heat); the engine does not check the extension. On save, every implemented component renders its configuration back to its file from the live model state, and a save-as carries the file alongside the written .inp.

Embedded form. The twelve [REACTION_*] sections may also be written directly in the .inp. They are captured verbatim by the input parser and applied after component resolution: when no external reactions component is registered they take effect with a style warning; when one is registered they are ignored with a warning and the external file wins wholesale. Embedded sections are not written back into the .inp on save — the writer warns that they are lost from the saved deck — so the external file is the intended layout. The heat, water-age and transport sections have no embedded form.

Cross-component references. [TRANSPORT_BOUNDARIES] and [TRANSPORT_SOURCES] rows name species declared in [REACTION_SPECIES], and the per-element rows of [RADIATIVE_FLUXES] and [SEDIMENT_EXCHANGE] name links, nodes and [TAGS] values. These are resolved once, after every component has applied, so the order of the [PROCESS_COMPONENTS] rows does not matter.

Component id	Configuration file	Sections	Status
`org.hydrocouple.openswmm.reactions`	`model.rxn` (or embedded in the `.inp`)	`[REACTION_OPTIONS]` `[REACTION_SPECIES]` `[REACTION_COEFFICIENTS]` `[REACTION_TERMS]` `[REACTION_PIPES]` `[REACTION_TANKS]` `[REACTION_QUALITY]`; `[REACTION_SOURCES]` `[REACTION_PARAMETERS]` `[REACTION_PATTERNS]` `[REACTION_REPORT]` are supported as described below; `[REACTION_SUBCATCHMENTS]` supplies wet non-LID pool laws	Implemented
`org.hydrocouple.openswmm.transport.ard`	`model.ard`	`[TRANSPORT_OPTIONS]` `[CONDUIT_DISPERSION]` `[TRANSPORT_BOUNDARIES]` `[TRANSPORT_SOURCES]`; `[STORAGE_MIXING]` is refused until phase E2b	Implemented
`org.hydrocouple.openswmm.transport.lard`	none	none — the Lagrangian engine is selected by `[OPTIONS] QUALITY_SOLVER LAGRANGIAN` (alias `LARD`) and reads no component file; registering this id is refused with "arrives with plan phase T5"	Planned
`org.hydrocouple.openswmm.heat`	`model.heat`	`[HEAT_SOURCES]` `[HEAT_FLUXES]` `[RADIATIVE_FLUXES]` `[SOLAR_RADIATION]` `[CLOUD_COVER]` `[SEDIMENT_EXCHANGE]`	Implemented
`org.hydrocouple.openswmm.waterage`	`model.age`	`[WATER_AGE_SOURCES]`	Implemented
`org.hydrocouple.openswmm.integrated2d`	none	none — unified 2D surface and two-zone groundwater component; registering this id is refused with "arrives with plan phase S1/G1"	Planned

The four implemented components are registered once, at the first open, so the id list above is the complete set a [PROCESS_COMPONENTS] row may name.

Component section: [REACTION_OPTIONS]

Purpose: Implemented Sets the integrator, coupling, units, tolerances and reference temperature of the reaction system.

Format:

SOLVER        EUL / RK5 / ROS2 / BDF2
COUPLING      NONE / FULL
RATE_UNITS    SEC / MIN / HR / DAY
AREA_UNITS    FT2 / M2 / CM2
WALL_GEOMETRY YES / NO
TIMESTEP      value
PATTERN_TIMESTEP value
ATOL          value
RTOL          value
TEMPERATURE   value

Parameters:

Parameter	Meaning	Units / values	Default
`SOLVER`	Integrator for the RATE species. RK5 is explicit and cheapest for non-stiff kinetics; ROS2 and BDF2 are implicit and are the remedy when RK5 reports its substep cap.	EUL, RK5, ROS2 or BDF2	RK5
`COUPLING`	NONE integrates one RATE species at a time with the others frozen at their start-of-step values (EPANET-MSX semantics); FULL integrates all RATE species simultaneously. A system with a single RATE species is always coupled.	NONE or FULL	NONE
`RATE_UNITS`	Time unit of every RATE expression. The evaluated rate is multiplied by 1, 1/60, 1/3600 or 1/86400 to give a per-second rate.	SEC, MIN, HR or DAY	HR
`AREA_UNITS`	Area basis for WALL geometry and dry buildup density.	FT2, M2 or CM2	FT2
`WALL_GEOMETRY`	Enable contact-area geometry and AV. Requires FULL coupling for WALL species.	YES or NO	NO
`TIMESTEP`	Reaction step; 0 means follow the quality step.	value, 0 or greater	0
`PATTERN_TIMESTEP`	Cyclic source-pattern interval, independent of RATE_UNITS.	seconds, > 0	3600
`ATOL`	Absolute tolerance of the integrator, used for every species that does not carry its own in `[REACTION_SPECIES]`.	value, greater than 0	1.0e-6
`RTOL`	Relative tolerance of the integrator, likewise.	value, greater than 0	1.0e-4
`TEMPERATURE`	Value of the expression variable `TEMP` for an element that has no heat-transport temperature (`HEAT_TRANSPORT OFF`, or before the heat state is seeded).	degrees C, any finite value	20

Remarks: Keys are case-insensitive and may appear in any order; a line with fewer than two tokens is skipped and an unrecognised key is an error. A bad value is an error naming the key. TEMPERATURE has no range gate — any finite number is accepted. AREA_UNITS and TIMESTEP are parsed, stored and written back on save; see the audit note at the end of this part for their consumers.

Component section: [REACTION_SPECIES]

Purpose: Implemented Declares the species of the reaction system. At least one species is required.

Format:

BULK / WALL Name Units (Atol Rtol)

Parameters:

Parameter	Meaning	Units / values	Default
Kind	BULK: a dissolved species carried with the water. WALL: a species attached to the wetted wall.	BULK or WALL	required
`Name`	Species name, unique among species, coefficients, terms, `[POLLUTANTS]` names and the reserved names.	text	required
`Units`	Concentration unit label recorded with the species (for example MG or UG). It is carried to the species registry and the reports; no conversion is applied.	text	required
`Atol`	Absolute tolerance for this species; 0 means use the global `ATOL`.	value	0
`Rtol`	Relative tolerance for this species; 0 means use the global `RTOL`.	value	0

Remarks: A row with fewer than three tokens, a kind other than BULK or WALL, a duplicate species name, or a name that collides with an existing pollutant or reserved species is an error. A configuration that declares no species is refused as a whole. Species are entered into the engine's species registry only after the complete file has validated and every expression has compiled, so a rejected file leaves no species behind.

Component section: [REACTION_COEFFICIENTS]

Purpose: Implemented Declares named numeric coefficients that expressions may reference.

Format:

PARAMETER / CONSTANT Name Value

Parameters:

Parameter	Meaning	Units / values	Default
Kind	PARAMETER: a coefficient that may be overridden per node or link. CONSTANT: a fixed value.	PARAMETER or CONSTANT	required
`Name`	Coefficient name, unique among coefficients and species.	text	required
`Value`	Numeric value.	value	required

Remarks: A row with fewer than three tokens, a kind other than PARAMETER or CONSTANT, a name that duplicates a coefficient or species, or a non-numeric value is an error. The kind keyword must be spelled in full — PARAM is not accepted. Both kinds evaluate identically in this release; the per-element override table that would distinguish them is [REACTION_PARAMETERS], which is not yet supported.

Component section: [REACTION_TERMS]

Purpose: Implemented Declares named intermediate expressions that pipe and tank expressions may reference, so a closure is defined once rather than copied.

Format:

Name Expression

Parameters:

Parameter	Meaning	Units / values	Default
`Name`	Term name, unique among terms, species and coefficients.	text	required
`Expression`	The remainder of the row, taken verbatim, including any unquoted commas. A remainder wrapped in double quotes is unwrapped.	expression	required

Remarks: A row with fewer than two tokens or a duplicate name is an error. Terms are compiled in file order and a term may reference only the terms declared before it (forward references are compile errors, reported with the term name and column). Expressions may reference species, coefficients, earlier terms, the hydraulic variables listed under [REACTION_PIPES], and [POLLUTANTS] names read-only.

Component section: [REACTION_PIPES]

Purpose: Implemented Gives each species its kinetic expression in the pipe (conduit) scope.

Format:

RATE / EQUIL / FORMULA Species Expression

Parameters:

Parameter	Meaning	Units / values	Default
Form	RATE: the expression is the time derivative of the species, in `RATE_UNITS`. EQUIL: the expression is an algebraic residual driven to zero. FORMULA: the expression is the species value itself.	RATE, EQUIL or FORMULA	required
`Species`	A species declared in `[REACTION_SPECIES]`.	text	required
`Expression`	The remainder of the row, taken verbatim (a double-quoted remainder is unwrapped).	expression	required

Remarks: A row with fewer than three tokens, an unknown form, an undeclared species, or a second expression for the same species in this scope is an error. Naming a [POLLUTANTS] row here is refused: pollutant kinetics arrive with plan phase R4b, and until then pollutants may only be referenced read-only inside expressions (their [POLLUTANTS] decay coefficient applies under every engine). A species with no row in this scope has no reaction in pipes. The hydraulic variables available to every expression, in the engine's internal units, are D depth (ft), Q flow (cfs), U velocity (ft/s), RE Reynolds number, US shear velocity (ft/s), FF Darcy-Weisbach friction factor, AV wetted surface area per volume (1/ft), HRT hydraulic residence time (s), DT reaction step (s) and TEMP water temperature (degrees C, falling back to [REACTION_OPTIONS] TEMPERATURE when heat transport is off). Variable names are case-insensitive. If the section is absent every species is given no pipe expression.

Component section: [REACTION_TANKS]

Purpose: Implemented Gives each species its kinetic expression in the tank (storage node) scope.

Format:

RATE / EQUIL / FORMULA Species Expression

Parameters:

Parameter	Meaning	Units / values	Default
Form	As for `[REACTION_PIPES]`.	RATE, EQUIL or FORMULA	required
`Species`	A species declared in `[REACTION_SPECIES]`.	text	required
`Expression`	The remainder of the row, taken verbatim.	expression	required

Remarks: The row grammar, validation rules and available variables are exactly those of [REACTION_PIPES]; the two sections share one parser and differ only in the scope they fill. A species may have a different form in each scope (for example a wall-demand term in pipes and none in tanks), and one expression per species per scope is the limit. If the section is absent every species is given no tank expression.

Component section: [REACTION_QUALITY]

Purpose: Implemented Sets the initial concentration of each species, globally and per element.

Format:

GLOBAL   Species   Value
NODE     Node      Species   Value
LINK     Link      Species   Value

Parameters:

Parameter	Meaning	Units / values	Default
Scope	GLOBAL applies to every element; NODE and LINK apply to one named element and win over GLOBAL there.	GLOBAL, NODE or LINK	required
`Node`, `Link`	Name of an existing node or link (NODE and LINK rows only).	text	required
`Species`	A species declared in `[REACTION_SPECIES]`.	text	required
`Value`	Initial concentration in the species' own units.	value, 0 or greater	0

Remarks: A scope other than GLOBAL, NODE or LINK, a row short of its fields, an unknown element, an undeclared species, a negative value, or a second NODE or LINK row for the same element and species is an error. Every species starts at 0 when it has no GLOBAL row, and when the section is absent altogether. Element names are resolved at open, after the full .inp has been read. Rows of [INITIAL_QUALITY] (Section: [INITIAL_QUALITY]) that name a reaction species are mirrored into this table, so an element may be seeded from either place; the same element and species in both is a duplicate error, and on save a mirrored row is written once, in [INITIAL_QUALITY]. The name REACTION_INITIAL that appears in some older prose is not recognised and is refused as an unknown section.

Component section: [REACTION_RAINFALL]

Purpose: Implemented Sets the concentration of each reaction species in rainfall, corresponding to the rain concentration column of [POLLUTANTS].

Format:

Species Concentration

Parameters:

Parameter	Meaning	Units / values	Default
`Species`	A species declared in `[REACTION_SPECIES]`.	text	required
`Concentration`	Species concentration in rainfall.	species' own concentration units, 0 or greater	0

Remarks: Omitted species have zero rainfall concentration; omitting the section gives clean rainfall for every reaction species. A row missing its concentration, an undeclared species, a nonnumeric or negative concentration, or a second row for the same species is an error. These values describe rainfall quality; initial concentrations are set separately in [REACTION_QUALITY] (Component section: [REACTION_QUALITY]). On save, only nonzero rainfall concentrations are written.

Component section: [REACTION_SOURCES]

Purpose: Implemented Adds species load at a named network node through the external mass-rate seam shared by LEGACY, EULERIAN_ARD and LAGRANGIAN.

Format:

CONC   Node   Species   Concentration   [Pattern]
MASS   Node   Species   MassRate        [Pattern]
FLOWPACED Node Species Concentration   [Pattern]
SETPOINT  Node Species Concentration   [Pattern]

CONC multiplies the concentration by positive external and dry-weather inflow water at that node. It creates no water. MASS is a rate in the species' declared mass units per second, independent of RATE_UNITS and project flow units. The engine divides it by 28.317 litres/ft³ at the load seam. These rows add to any [INFLOWS] and [DWF] species loads; avoid specifying the same intended load in both places. Values must be finite and nonnegative. Only BULK species are accepted; duplicate node/species rows, unknown nodes, species or patterns, and unknown source kinds are errors. Omitted pattern or * means constant.

FLOWPACED adds the specified concentration times arriving water volume to the mixed mass. Retained tank water is not dosed again merely because it remains in storage. SETPOINT adds the deficit needed to raise the complete mixed concentration to its target, only during positive water exchange; concentrations above the target are retained. Both require a physical mixing node and do nothing without arriving water or a wet mixed store. ARD applies its booster after each explicit node exchange, so the next face update uses that concentration. Patterns use the routing interval clock. The continuity report lists actual cumulative booster injection in declared species mass units. These semantics follow the EPA MSX manual.

Component section: [REACTION_PARAMETERS]

Purpose: Implemented Overrides a PARAMETER coefficient on one network element.

Format:

NODE Node Parameter Value

LINK Link Parameter Value

Values must be finite. CONSTANT coefficients cannot be overridden. Unknown references and duplicate element/parameter rows are errors. A missing row uses the current global coefficient. Terms and RATE, EQUIL and FORMULA expressions all see the element's override. An ARD cell uses its parent link's values; a Lagrangian segment uses its link's values. These overrides do not set 2D-cell, groundwater or LID-layer coefficients. Rows survive .rxn serialization.

Component section: [REACTION_PATTERNS]

Purpose: Implemented Defines cyclic, piecewise-constant multipliers for reaction node sources.

Format:

Pattern Factor1 [Factor2 ...]

Repeating a pattern name appends factors, allowing continuation rows. Factors must be finite and nonnegative. [REACTION_OPTIONS] PATTERN_TIMESTEP sets the interval in seconds, default 3600, and must be positive. Factor zero is selected at simulation start, subsequent factors at successive intervals, then the list wraps. The current inflow-assembly date selects the factor; use routing steps that resolve changes. The clock is derived from simulation time and needs no mutable pattern cursor. A new hotstart run starts its own pattern clock; exact native checkpoint continuation of reaction models is not yet supported.

Component section: [REACTION_REPORT]

Purpose: Implemented Selects reaction species columns in native output and output plugins using the engine's reported species list.

Format:

SPECIES ALL YES / NO

SPECIES Species YES / NO

The default is all species. An optional ALL baseline must precede named species overrides. Duplicate baselines or species, undeclared species, and values other than YES or NO are errors. Selected species retain declaration order and trail pollutants, water age and temperature. Hidden species still react and participate in other expressions. Their removal from output does not change the internal species stride or the selected columns' unit codes. Ordinary [REPORT] options continue to select nodes, links and subcatchments; this section does not independently select elements. The routing continuity summary reports BULK species only: a WALL density is not a water-volume mass.

Component section: [REACTION_SUBSURFACE]

Purpose: Implemented Defines explicit groundwater BULK-species reactions independently of the network pipe/tank and surface reaction laws.

Format:

*          SAT / UNSAT     Species RATE / EQUIL / FORMULA Expression
TAG  Name  SAT / UNSAT     Species RATE / EQUIL / FORMULA Expression
CELL Index SAT / UNSAT     Species RATE / EQUIL / FORMULA Expression
*          LAYER Layer    Species RATE / EQUIL / FORMULA Expression
TAG  Name  LAYER Layer    Species RATE / EQUIL / FORMULA Expression
CELL Index LAYER Layer    Species RATE / EQUIL / FORMULA Expression

Parameters: Name a mesh cell tag. Index 1-based unified mesh cell index. Layer 1-based unsaturated SIGMA layer index, counted from the surface downward. Species a declared BULK species from [REACTION_SPECIES]; WALL targets are refused. Expression kinetic rate, equilibrium residual or formula, according to the form; RATE follows [REACTION_OPTIONS] RATE_UNITS.

Remarks: Precedence is global *, then TAG, then CELL. Under layered unsaturated transport, UNSAT laws run independently in each active layer; explicit LAYER laws override them. A LAYER request must resolve to a valid SIGMA layer. No PIPE or TANK expression is silently substituted when this section is absent. The model must enable the aquifer and corresponding groundwater transport.

Expressions may use supported species, coefficients and intermediate terms, plus DT (seconds), TEMP (degrees C), GW_THETA, GW_POROSITY, GW_SE and GW_DEPTH_M (metres). Pipe-only variables, reachable WALL dependencies, disabled pollutant dependencies and duplicate first-order decay ownership are refused. Aqueous RATE kinetics use aqueous volume, rather than reacting sorbed inventory at the same rate.

Example (A and B must already be declared BULK species):

[REACTION_SUBSURFACE]
* SAT A RATE -0.001*A
* SAT B RATE 0.001*A

Component section: [REACTION_SUBCATCHMENTS]

Purpose: Implemented Defines a separate wet-pool reactor for each non-LID subcatchment.

Format:

RATE / EQUIL / FORMULA Species Expression

SUBCATCHMENT Name RATE / EQUIL / FORMULA Species Expression

Global rows apply everywhere; a named row overrides that species on that subcatchment. Without global rows, unselected subcatchments retain their ordinary surface-quality closure. Duplicate named subcatchment/species rows are errors.

Only BULK targets and BULK dependencies are supported. Constants, global PARAMETER coefficients, terms, DT (seconds) and TEMP (degrees C) are available. With heat enabled TEMP is the beginning-of-step published runoff temperature; otherwise it is the configured fallback. Other hydraulic variables, pollutant references and WALL references (including through terms) are refused. NODE/LINK parameter overrides do not affect this scope.

Each runoff step mixes retained ponded mass with rainfall and run-on inputs, integrates that pool over the runoff interval, then allocates its mass to infiltration, runoff and retained storage. Closing storage carries the remaining mass; evaporation removes water without removing solute. This is a first-order split batch model: incoming mass is mixed before reacting for the full interval. Resolve kinetic and forcing time scales with WET_STEP and check timestep sensitivity. It is not an exact continuously fed CSTR.

Zero-volume pools do not react. Pools at or below one litre retain and route their mass without integrating concentrations. Dry residual mass is booked as remaining dry mass through the existing ponded-loss ledger. RATE overshoots are clamped with separate reaction-loss and clamp-addition rows; failed or negative algebraic steps retain the unreacted mixed inventory and warn. Reaction mass changes are recorded in runoff quality continuity.

Dry buildup has its own scope below. Network pipe/tank laws do not substitute for surface laws. LID units must explicitly opt into their layer adapter. Full native checkpoints carry wet/dry inventories in the qualified 1D profile.

Component section: [REACTION_BUILDUP]

Purpose: Implemented React the dry inventory on a covered land-use patch before accrual, sweeping and washoff. This is a first-order operator split.

LANDUSE Name RATE / EQUIL / FORMULA Species Expression

SUBCATCHMENT Name LANDUSE Name RATE / EQUIL / FORMULA Species Expression

A named-subcatchment row overrides a global land-use row for that species. Targets/dependencies must be BULK; global coefficients, terms, DT and fallback TEMP are available. Values are declared species mass per AREA_UNITS. Each species' area/curb normalizer and project mass conversion are applied before and after integration, so mixed normalizers share one physical patch area. A zero curb normalizer cannot retain reaction products: the solve is refused with a warning and original inventory retained. Failed algebraic solves and RATE clamps follow wet-pool containment and explicit mass accounting. Reaction products persist even without a buildup accrual function. Equal mass-unit, unit-yield networks conserve parent plus product; different units require explicit conversion in the authored law.

Component section: [REACTION_WALLS]

NODE / LINK Name ContactArea

Areas must be finite/nonnegative in AREA_UNITS and require WALL_GEOMETRY YES. Conduits without an override use actual wetted perimeter times physical length times barrel count. Their fixed reference is full-section contact. Storage-node WALL tank laws require explicit NODE area; other storage shape is not inferred. AV is active contact area / litres of water. WALL density is declared mass / reference area. WALL RATE expressions scale by active/reference contact; dry and sub-litre geometry-mode pools retain attached mass and skip kinetics. WALL EQUIL/FORMULA projections are refused because no conservative wet/dry area projection is defined. ARD WALL systems use LEGACY; LARD refuses WALL.

Component section: [REACTION_LIDS]

CONTROL Name TRANSPORT

CONTROL Name LAYER Number RATE / EQUIL / FORMULA Species Expression

TRANSPORT opts a control into BULK mobile/retained species inventories; a law also opts it in. Layer 0 supplies defaults; a specific layer overrides that species. Conventional layers are 1 surface, 2 pavement, 3 soil, 4 storage. Storage-node layers use authored stack numbers. Missing layers do not react. Only BULK references, global coefficients, terms, DT and beginning-of-step published layer TEMP (fallback TEMPERATURE) are supported. Laws apply per retained pool and mobile layer share; pipe/tank laws do not replace them.

Storage-node bucket/Richards reactors require LEGACY quality and non-Mesh bottoms. Conventional units require full subcatchment coverage (the hydraulic 0.1% area tolerance) and every unit to opt in; uncovered barrels are permitted. Partial capture, covered barrels, WALL species and 2D-owned reactive conventional units are refused. Transport consumes accepted hydraulic transfers with donor limits, water-only evaporation, separate infiltration/surface/drain receipts, BMP removals and dry residual mass. Pools at or below one litre do not react; zero-storage throughflow layers transport mass without inventing a reactor. Bioretention and permeable-pavement stacks, plus bucket/Richards storage nodes, have explicit conservation/restart checks; wider configurations still need qualification. State-only and legacy routing hotstarts refuse these inventories; use a full native engine checkpoint.

Full reaction continuation currently qualifies native CPU 1D chemistry without pollutants, heat/age, active 2D surface chemistry, subsurface laws or detailed ARD/LID output. It preserves source clocks, inventories, ledgers and native output prefixes; changed chemistry or corrupt state is refused before install.

Component section: [HEAT_SOURCES]

Purpose: Implemented Sets the temperature carried by water entering the network through each source pathway, globally and per node.

Format:

Source GLOBAL Temperature

Source NODE Node Temperature

Parameters:

Parameter	Meaning	Units / values	Default
`Source`	The inflow pathway: RAINFALL (runoff), DWF (dry-weather inflow), GW (groundwater), RDII, EXTERNAL_INFLOW (`[INFLOWS]` rows), IFACE (interface-file inflow) or INITIAL_STATE (water in the network at the start).	keyword	required
Scope	GLOBAL sets the pathway everywhere; NODE sets it at one node and wins there.	GLOBAL or NODE	required
`Node`	Name of an existing node (NODE rows only).	text	required
`Temperature`	Inlet temperature.	degrees C, from -50 to 100	20

Remarks: Every pathway without a row enters at 20 degrees C. NODE scope is available for DWF and EXTERNAL_INFLOW only; any other source takes GLOBAL. A row with fewer than three tokens, an unknown source, an unknown node, a temperature outside the range, or a second NODE row for the same source and node is an error. SUBCATCH scope ("arrives with plan phase H5") and EDGE_BC scope ("arrives with phase T6") are refused, and a TIMESERIES in place of the value is refused — this table takes constant temperatures. Any error discards the whole heat configuration. The component warns when [OPTIONS] HEAT_TRANSPORT is OFF, because then no temperature is tracked.

Component section: [HEAT_FLUXES]

Purpose: Implemented Switches the energy-flux modules on or off and chooses what a dry element reports. With every module off, temperature is carried and mixed as a conservative tracer.

Format:

SURFACE_EXCHANGE          ON / OFF
RADIATIVE_EXCHANGE        ON / OFF
LAYER_CONDUCTION          ON / OFF
SEDIMENT_EXCHANGE         ON / OFF
DRY_ELEMENT_TEMPERATURE   HOLD / AIR / DEFAULT

Parameters:

Parameter	Meaning	Units / values	Default
`SURFACE_EXCHANGE`	Latent and sensible exchange at the free surface, driven by the `[TEMPERATURE]` climate data.	ON or OFF	OFF
`RADIATIVE_EXCHANGE`	Shortwave and longwave exchange, parameterised by `[RADIATIVE_FLUXES]`, `[SOLAR_RADIATION]` and `[CLOUD_COVER]`.	ON or OFF	OFF
`LAYER_CONDUCTION`	Vertical conduction between LID layers. Its material constants are built in; no section configures them.	ON or OFF	OFF
`SEDIMENT_EXCHANGE`	The bed zone beneath conduits — conduction to the bed and deep ground plus hyporheic exchange — parameterised by `[SEDIMENT_EXCHANGE]`.	ON or OFF	OFF
`DRY_ELEMENT_TEMPERATURE`	What a dry element reports: HOLD freezes the last wet value; AIR tracks air temperature; DEFAULT falls to 20 degrees C.	HOLD, AIR or DEFAULT	HOLD

Remarks: Each row is exactly two tokens; YES and NO are accepted for ON and OFF. An unknown module name, a toggle value other than these four, or a DRY_ELEMENT_TEMPERATURE value other than the three policies is an error. Every module defaults OFF so that a deck gets pure transport unless it asks for physics. The parameter sections may be present while their module is OFF; they are then parsed and validated but have no effect. SEDIMENT_EXCHANGE here is the toggle; the section of the same name holds its parameters.

Component section: [RADIATIVE_FLUXES]

Purpose: Implemented Supplies the incoming shortwave resource and the optical properties of the water surface and its surroundings for RADIATIVE_EXCHANGE.

Format:

SHORTWAVE            GLOBAL   Value
SHORTWAVE            GLOBAL   TIMESERIES   Name
SHORTWAVE            GLOBAL   COMPUTED
ATM_EMISS_COEFF      GLOBAL   Value
ATM_LW_REFLECTION    GLOBAL   Value
Parameter            GLOBAL   Value
Parameter            TAG / LINK / NODE   Name   Value

Parameters:

Parameter	Meaning	Units / values	Default
`SHORTWAVE`	Incoming solar radiation: a constant, a `[TIMESERIES]` of measured values, or COMPUTED from solar position and a clear-sky atmosphere using `[SOLAR_RADIATION]`. GLOBAL only.	W/m2, 0 or greater; or TIMESERIES name; or COMPUTED	0 (constant)
`ALBEDO`	Shortwave reflectance of the water surface.	fraction 0 to 1	0
`SHADE_FACTOR`	Fraction of insolation blocked by shading.	fraction 0 to 1	0
`SKY_VIEW`	Fraction of the hemisphere above the water that is sky rather than land cover.	fraction 0 to 1	1
`EMISS_WATER`	Longwave emissivity of the water surface.	fraction 0 to 1	0.97
`EMISS_LANDCOVER`	Longwave emissivity of the surrounding land cover.	fraction 0 to 1	0.97
`LANDCOVER_TEMPERATURE`	Radiating temperature of the land cover. When unset, air temperature is used.	degrees C, any finite value	air temperature
`ATM_EMISS_COEFF`	Brunt clear-sky atmospheric emissivity coefficient. GLOBAL only.	fraction 0 to 1	0.5
`ATM_LW_REFLECTION`	Longwave reflectance of the water surface. GLOBAL only.	fraction 0 to 1	0.03

Remarks: Every row carries a scope token. SHORTWAVE, ATM_EMISS_COEFF and ATM_LW_REFLECTION describe the incident resource or the atmosphere and are refused at any scope but GLOBAL; the six surface parameters accept GLOBAL, TAG, LINK or NODE, where TAG matches every link and node carrying that value in [TAGS] (Section: [TAGS]). Precedence is GLOBAL, then TAG, then the named element. A TAG that matches nothing, an unknown link or node, or two rows for the same parameter at the same scope and name are errors. The three SHORTWAVE spellings are mutually exclusive: a second SHORTWAVE row is an error, not an override. COMPUTED requires [SOLAR_RADIATION] LATITUDE and LONGITUDE (they are never taken from the [TEMPERATURE] snowmelt line) and takes no further token; TIMESERIES names an existing [TIMESERIES]. Fractions are refused outside 0 to 1 rather than clamped, and a non-finite value is refused. The section has no effect unless [HEAT_FLUXES] RADIATIVE_EXCHANGE is ON.

Component section: [SOLAR_RADIATION]

Purpose: Implemented Gives the site position and the clear-sky atmosphere used when [RADIATIVE_FLUXES] SHORTWAVE is COMPUTED.

Format:

LATITUDE        GLOBAL   Value
LONGITUDE       GLOBAL   Value
TIMEZONE        GLOBAL   Value
ELEVATION       GLOBAL   Value
TURBIDITY_380   GLOBAL   Value
TURBIDITY_500   GLOBAL   Value
PRECIP_WATER    GLOBAL   Value
OZONE           GLOBAL   Value
GROUND_ALBEDO   GLOBAL   Value

Parameters:

Parameter	Meaning	Units / values	Default
`LATITUDE`	Site latitude, positive north. Required under COMPUTED.	degrees, -90 to 90	none
`LONGITUDE`	Site longitude, positive east. Required under COMPUTED.	degrees, -180 to 180	none
`TIMEZONE`	Offset of the deck's clock from UTC, positive east (for example -7 for MST).	hours, -14 to 14	0 (UTC)
`ELEVATION`	Site elevation for the atmospheric pressure term. When unset the `[TEMPERATURE]` climate elevation is used.	metres, -500 to 9000	climate elevation
`TURBIDITY_380`	Aerosol optical depth at 380 nm.	value, 0 or greater	0.30
`TURBIDITY_500`	Aerosol optical depth at 500 nm.	value, 0 or greater	0.20
`PRECIP_WATER`	Precipitable water vapour column.	cm, 0 or greater	1.42
`OZONE`	Ozone column at NTP.	cm, 0 or greater	0.34
`GROUND_ALBEDO`	Albedo of the ground around the site, for the sky-ground multiple-reflection term. This is not the water's `ALBEDO`.	fraction 0 to 1	0.20

Remarks: Every row is exactly Parameter GLOBAL Value; there is no per-element scope. Ranges are refused rather than clamped (a latitude of 100 is a typo, not the pole), and a non-finite value is refused. The atmosphere defaults are the Bird and Hulstrom standard atmosphere. The section is consulted only under SHORTWAVE GLOBAL COMPUTED: when coordinates are given under another SHORTWAVE spelling the component warns that they are unused, and when COMPUTED is in force without a TIMEZONE it warns that local time is taken as UTC, which can shift the computed solar day by up to 12 hours.

Component section: [CLOUD_COVER]

Purpose: Implemented Gives one cloud fraction that attenuates the shortwave resource and raises the atmospheric longwave emissivity, with the coefficients of both corrections.

Format:

FRACTION     GLOBAL   Value
FRACTION     GLOBAL   TIMESERIES   Name
SW_ATTEN_K   GLOBAL   Value
SW_ATTEN_N   GLOBAL   Value
LW_CLOUD_K   GLOBAL   Value

Parameters:

Parameter	Meaning	Units / values	Default
`FRACTION`	Cloud fraction, constant or from a `[TIMESERIES]`.	fraction 0 to 1; or TIMESERIES name	0 (clear sky)
`SW_ATTEN_K`	Kasten-Czeplak shortwave attenuation coefficient k.	value, 0 or greater	0.75
`SW_ATTEN_N`	Kasten-Czeplak shortwave attenuation exponent n.	value, 0 or greater	3.4
`LW_CLOUD_K`	Bolz longwave cloud coefficient.	value, 0 or greater	0.17

Remarks: Every row is Parameter GLOBAL Value; a constant FRACTION outside 0 to 1 is refused (it is a fraction, not a percent), while a TIMESERIES value is clamped at run time. An unknown parameter, a negative coefficient or a non-finite value is an error. Both corrections are the identity at a fraction of 0, so a section holding coefficients but no FRACTION row has no effect and the component warns. It also warns when [CLOUD_COVER] is combined with SHORTWAVE GLOBAL TIMESERIES, because a measured record already contains its clouds and would be attenuated twice; the longwave correction still applies. The section has no effect unless RADIATIVE_EXCHANGE is ON.

Component section: [SEDIMENT_EXCHANGE]

Purpose: Implemented Parameterises the bed zone beneath conduits for [HEAT_FLUXES] SEDIMENT_EXCHANGE: conduction to the bed and the deep ground, and hyporheic exchange of heat and dissolved species.

Format:

Parameter             GLOBAL   Value
Parameter             TAG / LINK   Name   Value
GROUND_TEMPERATURE    GLOBAL   TIMESERIES   Name
INITIAL_TEMPERATURE   GLOBAL   Value

Parameters:

Parameter	Meaning	Units / values	Default
`THERMAL_DIFFUSIVITY`	Bed thermal diffusivity.	m2/s, greater than 0	1.0e-6
`SOLUTE_DIFFUSIVITY`	Bed effective solute diffusivity, one value for every species; 0 selects advection-only exchange.	m2/s, 0 or greater	1.0e-9
`BED_THICKNESS`	Thickness of the bed layer — the conduction length and the bed's heat capacity.	m, greater than 0	0.20
`GROUND_DEPTH`	Depth from the bed to the deep-ground boundary.	m, greater than 0	2.0
`GROUND_TEMPERATURE`	Deep-ground temperature, constant or (GLOBAL only) from a `[TIMESERIES]`.	degrees C, any finite value; or TIMESERIES name	12.0
`HYPORHEIC_VELOCITY`	Exchange velocity across the bed interface; 0 means conduction only. Direction follows the gradient, so a negative value is refused.	m/s, 0 or greater	0
`SEDIMENT_DENSITY`	Bed bulk density.	kg/m3, greater than 0	1670
`SEDIMENT_SPECIFIC_HEAT`	Bed specific heat.	J/kg/K, greater than 0	1807
`INITIAL_TEMPERATURE`	Initial bed temperature. GLOBAL only.	degrees C, any finite value	the ground temperature

Remarks: The bed exists beneath conduits only, so NODE scope is refused; the first eight parameters accept GLOBAL, TAG or LINK, with TAG matching every link carrying that value in [TAGS] and precedence GLOBAL, then TAG, then LINK. INITIAL_TEMPERATURE has no per-element form. Lengths, diffusivities and material properties are refused at or below zero rather than clamped, because each is a divisor or a capacity in the exchange kernel. A TAG that matches nothing, an unknown link, a duplicate row at the same scope and name, or a non-finite value is an error. GROUND_TEMPERATURE has a default but is worth stating, since the ground term is often the largest in a buried pipe. Under the Eulerian engine every transport cell carries its own bed slice; under the other engines the bed exchanges with the link's mean temperature. The section has no effect unless [HEAT_FLUXES] SEDIMENT_EXCHANGE is ON.

Component section: [WATER_AGE_SOURCES]

Purpose: Implemented Sets the age carried by water entering the network through each source pathway, globally and per node, for [OPTIONS] WATER_AGE ON.

Format:

Source GLOBAL Hours

Source NODE Node Hours

Parameters:

Parameter	Meaning	Units / values	Default
`Source`	The inflow pathway: RAINFALL (runoff), DWF, GW, RDII, EXTERNAL_INFLOW (`[INFLOWS]` rows), IFACE (interface-file inflow) or INITIAL_STATE (water in the network at the start).	keyword	required
Scope	GLOBAL sets the pathway everywhere; NODE sets it at one node and wins there.	GLOBAL or NODE	required
`Node`	Name of an existing node (NODE rows only).	text	required
`Hours`	Age of the arriving water. A negative age extracts age-volume (the receiving water reads younger) and is warned; extraction clamps so age never falls below zero.	hours, any number	0 (fresh)

Remarks: Ages are entered in hours and held internally in seconds. Every pathway without a row enters fresh. NODE scope is available for DWF and EXTERNAL_INFLOW only; any other source takes GLOBAL. A row with fewer than three tokens, an unknown source, an unknown node, a non-numeric age, or a second NODE row for the same source and node is an error, as is any section in the file other than this one. SUBCATCH scope ("arrives with plan phase A3") and EDGE_BC scope ("arrives with phase T6") are refused. A TIMESERIES in place of the value is refused with a redirect: a time-varying inflow age is written as an [INFLOWS] row naming the reserved constituent __WATER_AGE__ (Section: [INFLOWS]), and such a row wins over this table's EXTERNAL_INFLOW entry at that node. Any error discards the whole water-age configuration. The component warns when [OPTIONS] WATER_AGE is OFF, because then no age is tracked. A zero-valued GLOBAL row is not written back on save, since zero is the default.

Component section: [TRANSPORT_OPTIONS]

Purpose: Implemented Configures the Eulerian advection-reaction-dispersion engine selected by [OPTIONS] QUALITY_SOLVER EULERIAN_ARD: the dispersion model, the scalar advection scheme, the transport mesh and a per-cell diagnostic output.

Format:

DISPERSION        OFF / FISCHER / Value
SCALAR_SCHEME     UPWIND / MUSCL / QUICKEST_ULTIMATE
LIMITER           MINMOD / VANLEER / SUPERBEE
TARGET_DX         Value
DETAILED_OUTPUT   Path

Parameters:

Parameter	Meaning	Units / values	Default
`DISPERSION`	Global longitudinal dispersion model. OFF applies none; FISCHER computes \(D = 0.011\,v^{2} B^{2} / (Y\,U_{})\) with \(U_{} = \sqrt{g Y S}\) per cell; a number applies one uniform coefficient.	OFF, FISCHER, or a coefficient in display units of length squared per second (m2/s under SI flow units, ft2/s under US), 0 or greater	OFF
`SCALAR_SCHEME`	Face reconstruction of the transported scalars. An alias of `[OPTIONS] FV_SCALAR_SCHEME`; this file wins because the component applies after the options.	UPWIND, MUSCL or QUICKEST_ULTIMATE	MUSCL
`LIMITER`	Slope limiter for the higher-order schemes. An alias of `[OPTIONS] FV_LIMITER`.	MINMOD, VANLEER or SUPERBEE	MINMOD
`TARGET_DX`	Transport-mesh cell length under non-FV hydraulic routing. Under `FLOW_ROUTING FV` the solver mesh governs and this key is ignored with a warning.	display length units, greater than 0	0 (the `FV_CELL_LENGTH` rules)
`DETAILED_OUTPUT`	Path of a per-cell CSV sidecar written during the run. A relative path resolves against the directory of the component file, not the `.inp`.	path	none

Remarks: Keys are case-insensitive and each takes exactly one argument; an unknown key or a malformed value is an error, and any error discards the whole transport configuration. Per-conduit dispersion overrides are given in the companion section [CONDUIT_DISPERSION] of the same file, one Conduit Value row each (non-conduit links and duplicate rows are refused); an override wins over the global model in its conduit, including when DISPERSION is OFF. A [STORAGE_MIXING] section is recognised and refused ("arrives with plan phase E2b"). Because SCALAR_SCHEME and LIMITER write through to the [OPTIONS] values and the .inp writer emits FV_* keys only under FLOW_ROUTING FV, this file is the carrier of those choices across a save on a non-FV deck; a file that never spelled the alias never gains one. [OPTIONS] FV_DISPERSION does not configure this engine and is warned about when set. The component warns at open whenever its content can reach nothing: IGNORE_QUALITY YES, a QUALITY_SOLVER other than EULERIAN_ARD, or dispersion configured with no [POLLUTANTS] and no reactions component.

Component section: [CONDUIT_DISPERSION]

Purpose: Implemented Overrides, for individual conduits, the longitudinal dispersion coefficient the Eulerian ARD engine takes from [TRANSPORT_OPTIONS] DISPERSION.

Format:

Conduit Value

Parameters:

Parameter	Meaning	Units / values	Default
Conduit	Name of an existing conduit. A pump, orifice, weir or outlet is refused: structures are zero-volume pass-throughs and carry no dispersion.	link name	—
Value	Longitudinal dispersion coefficient for that conduit.	project length squared per second, finite and non-negative	the `[TRANSPORT_OPTIONS] DISPERSION` value

Remarks: One row per conduit; a second row for the same conduit is an error. Rows are validated when the component configuration is applied, so an unknown link name fails the open (or, under a lenient open, discards the whole configuration). See quality §7.3.3 for how the coefficient enters the implicit dispersion update.

Component section: [STORAGE_MIXING]

Purpose: Planned Per-storage-node mixing models for the Eulerian ARD engine. The section name is recognised by the parser, and any content under it is refused with an error naming the plan phase that delivers it (E2b); leave the section out of a configuration file.

Format:

(no rows are accepted this release)

Remarks: Storage nodes are complete-mix reactors under every transport engine in this release (quality §7.3). The section is listed here so that a file carrying it is understood rather than mistaken for a typo.

Component section: [TRANSPORT_BOUNDARIES]

Purpose: Implemented Sets the concentration of a reaction species carried by the external inflow water entering at a node, under the Eulerian engine.

Format:

Node Species VALUE Concentration

Node Species TIMESERIES Name

Parameters:

Parameter	Meaning	Units / values	Default
`Node`	Name of an existing node.	text	required
`Species`	A species declared in the reactions component's `[REACTION_SPECIES]`.	text	required
Mode	VALUE gives a constant; TIMESERIES names a `[TIMESERIES]` of concentrations.	VALUE or TIMESERIES	required
`Concentration`, `Name`	The constant concentration in the species' own units, or the series name.	value, 0 or greater; or text	required

Remarks: Every row is exactly four tokens; a mode other than VALUE or TIMESERIES, or a negative or non-numeric VALUE, is an error at parse. The node, the species and the series are resolved after every component has applied, so the reactions row may precede or follow the transport row in [PROCESS_COMPONENTS]; an unknown node, an unknown series, an undeclared species, or a second row for the same node and species is then an error. A [POLLUTANTS] name is refused: pollutants keep their [INFLOWS], dry-weather and washoff loading pathways, and allowing them here would double-count. The concentration applies to the node's external inflow water only; it is not a fixed concentration at the node. Rows are inert, with a warning, unless QUALITY_SOLVER is EULERIAN_ARD and IGNORE_QUALITY is NO.

Component section: [TRANSPORT_SOURCES]

Purpose: Implemented Applies a distributed mass rate of a reaction species along a conduit, independent of its flow, under the Eulerian engine. A negative rate extracts.

Format:

Conduit Species VALUE Rate

Conduit Species TIMESERIES Name

Parameters:

Parameter	Meaning	Units / values	Default
`Conduit`	Name of an existing conduit. Other link types are refused.	text	required
`Species`	A species declared in the reactions component's `[REACTION_SPECIES]`.	text	required
Mode	VALUE gives a constant; TIMESERIES names a `[TIMESERIES]` of rates.	VALUE or TIMESERIES	required
`Rate`, `Name`	The constant mass rate in the species' mass units per second, or the series name.	value, any sign; or text	required

Remarks: Every row is exactly four tokens; a mode other than VALUE or TIMESERIES, or a non-numeric VALUE, is an error at parse. The conduit, the species and the series are resolved after every component has applied; a link that is not a conduit, an unknown series, an undeclared species, a [POLLUTANTS] name, or a second row for the same conduit and species is then an error. The rate is spread over the conduit's cells in proportion to cell length. A negative VALUE is accepted as extraction and warned once at open; a series that dips negative extracts likewise. Extraction is clamped to the mass the cells actually hold, and the unmet portion is counted and summarised at the end of the run. The mass rate is converted internally by dividing by 28.316846592 litres per cubic foot, since the engine's store is concentration times cubic feet. Rows are inert, with a warning, unless QUALITY_SOLVER is EULERIAN_ARD and IGNORE_QUALITY is NO.

Section: [LID_LAYER_TREATMENT]

Control Layer Pollutant RemovalPercent DecayPerDay [Expression] assigns one pollutant rule to a physical NODE layer (one-based from the top; BOTTOM is excluded). Removal is 0–100%; decay is nonnegative in 1/day. Optional R = ... or C = ... expressions act after fixed removal. Use Dynamic Wave and QUALITY_SOLVER LEGACY. See CHAPTER 6 — Storage-node LIDs: Implementation and Interfaces for conservative coupling, treatment order, API behavior, persistence and numerical limits.

Table of Contents

2.1 General Instructions

2.2 Input File Format

Section: [TITLE]

Section: [OPTIONS]

Units and process models

Dates and times

Time steps

Reporting

Dynamic wave solver

Pressurisation and friction

Finite-volume routing (FV_*)

Water quality and transport

Heat transport

2D, coordinate reference and files

Miscellaneous

Retired keywords

Section: [REPORT]

Section: [FILES]

Section: [RAINGAGES]

Section: [EVAPORATION]

Section: [TEMPERATURE]

Energy-balance snow and shared radiation

Section: [UEB_OPTIONS]

Section: [ADJUSTMENTS]

Section: [SUBCATCHMENTS]

Section: [SUBAREAS]

Section: [INFILTRATION]

Section: [LID_NODES]

Section: [LID_NODE_OUTLETS]

Section: [LID_RICHARDS]

Section: [LID_CONTROLS]

Section: [LID_USAGE]

Section: [AQUIFERS]

Section: [GROUNDWATER]

Section: [GWF]

Section: [SNOWPACKS]

UEB site and model override

Section: [JUNCTIONS]

Section: [OUTFALLS]

Section: [DIVIDERS]

Section: [STORAGE]

Section: [CONDUITS]

Section: [PUMPS]

Section: [ORIFICES]

Section: [WEIRS]

Section: [OUTLETS]

Section: [XSECTIONS]

Section: [TRANSECTS]

Section: [STREETS]

Section: [INLETS]

Section: [INLET_USAGE]

Section: [LOSSES]

Section: [CONTROLS]

Section: [POLLUTANTS]

Section: [LANDUSES]

Section: [COVERAGES]

Section: [LOADINGS]

Section: [BUILDUP]

Section: [WASHOFF]

Section: [TREATMENT]

Section: [INFLOWS]

Section: [DWF]

Section: [RDII]

Section: [HYDROGRAPHS]

Section: [CURVES]

Section: [TIMESERIES]

Section: [PATTERNS]

Section: [VIRTUAL_JUNCTIONS]

Section: [INLET_JUNCTIONS]

Section: [INITIAL_QUALITY]

Section: [RDII_DECAY]

Section: [EVENTS]

Section: [TAGS]

Section: [PROFILE]

Section: [PROFILES]

Section: [USER_FLAGS]

Section: [USER_FLAG_VALUES]

Section: [PLUGINS]

Section: [PROCESS_COMPONENTS]