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OpenSWMM Engine
6.0.0-alpha.4
Data-oriented, plugin-extensible SWMM Engine (6.0.0-alpha.4)
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OpenSWMM Engine
6.0.0-alpha.4
Data-oriented, plugin-extensible SWMM Engine (6.0.0-alpha.4)
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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.
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. Appendix A.1 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.
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.
Purpose: Provides values for various analysis options.
Format: FLOW_UNITS CFS / GPM / MGD / CMS / LPS / MLD INFILTRATI0N HORTON / MODIFIED_HORTON / GREEN_AMPT / MODIFIED_GREEN_AMPT / CURVE_NUMBER FLOW_ROUTING STEADY / KINWAVE / DYNWAVE LINK_OFFSETS DEPTH / ELEVATION FORCE_MAIN_EQUATION H-W / D-W IGNORE_RAINFALL YES / NO IGNORE_SNOWMELT YES / NO IGNORE_GROUNDWATER YES / NO IGNORE_RDII YES / NO IGNORE_ROUTING YES / NO IGNORE_QUALITY YES / NO ALLOW_PONDING YES / NO SKIP_STEADY_STATE YES / NO SYS_FLOW_TOL value LAT_FLOW_TOL value START_DATE month/day/year START_TIME hours:minutes END_DATE month/day/year END_TIME hours:minutes REPORT_START_DATE month/day/year REPORT_START_TIME hours:minutes SWEEP_START month/day SWEEP_END month/day DRY_DAYS days REPORT_STEP hours:minutes:seconds WET_STEP hours:minutes:seconds DRY_STEP hours:minutes:seconds ROUTING_STEP seconds LENGTHENING_STEP seconds VARIABLE_STEP value MINIMUM_STEP seconds INERTIAL_DAMPING NONE / PARTIAL / FULL NORMAL_FLOW_LIMITED SLOPE / FROUDE / BOTH SURCHARGE_METHOD EXTRAN / SLOT / DYNAMIC_SLOT / TPA MIN_SURFAREA value MIN_SLOPE value MAX_TRIALS value HEAD_TOLERANCE value THREADS value
Remarks: FLOW_UNITS makes a choice of flow units. Selecting a US flow unit means that all other quantities will be expressed in US customary units, while choosing a metric flow unit will force all quantities to be expressed in SI metric units. (Exceptions are pollutant concentration and Manning’s roughness coefficient (n) which are always in metric units). The default is CFS. INFILTRATION selects a model for computing infiltration of rainfall into the upper soil zone of subcatchments. The default model is HORTON. FLOW_ROUTING determines which method is used to route flows through the drainage system. STEADY refers to sequential steady state routing (i.e. hydrograph translation), KINWAVE to kinematic wave routing, DYNWAVE to dynamic wave routing. The default routing method is DYNWAVE. LINK_OFFSETS determines the convention used to specify the position of a link offset above the invert of its connecting node. DEPTH indicates that offsets are expressed as the distance between the node invert and the link while ELEVATION indicates that the absolute elevation of the offset is used. The default is DEPTH.
FORCE_MAIN_EQUATION establishes whether the Hazen-Williams (H-W) or the Darcy-Weisbach (D-W) equation will be used to compute friction losses for pressurized flow in conduits that have been assigned a Circular Force Main cross-section shape. The default is H-W. IGNORE_RAINFALL is set to YES if all rainfall data and runoff calculations should be ignored. In this case SWMM only performs flow and pollutant routing based on user-supplied direct and dry weather inflows. The default is NO. IGNORE_SNOWMELT is set to YES if snowmelt calculations should be ignored when a project file contains snow pack objects. The default is NO. IGNORE_GROUNDWATER is set to YES if groundwater calculations should be ignored when a project file contains aquifer objects. The default is NO. IGNORE_RDII is set to YES if rainfall-dependent infiltration and inflow should be ignored when RDII unit hydrographs and RDII inflows have been supplied to a project file. The default is NO. IGNORE_ROUTING is set to YES if only runoff should be computed even if the project contains drainage system links and nodes. The default is NO. IGNORE_QUALITY is set to YES if pollutant washoff, routing, and treatment should be ignored in a project that has pollutants defined. The default is NO. ALLOW_PONDING determines whether excess water is allowed to collect atop nodes and be re-introduced into the system as conditions permit. The default is NO ponding. In order for ponding to actually occur at a particular node, a non-zero value for its Ponded Area attribute must be used. SKIP_STEADY_STATE should be set to YES if flow routing computations should be skipped during steady state periods of a simulation during which the last set of computed flows will be used. A time step is considered to be in steady state if the percent difference between total system inflow and total system outflow is below the SYS_FLOW_TOL and the percent difference between current and previous lateral inflows are below the LAT_FLOW_TOL. The default for this option is NO. SYS_FLOW_TOL is the maximum percent difference between total system inflow and total system outflow which can occur in order for the SKIP_STEADY_STATE option to take effect. The default is 5 percent. LAT_FLOW_TOL is the maximum percent difference between the current and previous lateral inflow at all nodes in the conveyance system in order for the SKIP_STEADY_STATE option to take effect. The default is 5 percent. START_DATE is the date when the simulation begins. If not supplied, a date of 1/1/2004 is used. START_TIME is the time of day on the starting date when the simulation begins. The default is 12 midnight (0:00:00). END_DATE is the date when the simulation is to end. The default is the start date. END_TIME is the time of day on the ending date when the simulation will end. The default is 24:00:00. REPORT_START_DATE is the date when reporting of results is to begin. The default is the simulation start date. REPORT_START_TIME is the time of day on the report starting date when reporting is to begin. The default is the simulation start time of day. SWEEP_START is the day of the year (month/day) when street sweeping operations begin. The default is 1/1. SWEEP_END is the day of the year (month/day) when street sweeping operations end. The default is 12/31. DRY_DAYS is the number of days with no rainfall prior to the start of the simulation. The default is 0. REPORT_STEP is the time interval for reporting of computed results. The default is 0:15:00. WET_STEP is the time step length used to compute runoff from subcatchments during periods of rainfall or when ponded water still remains on the surface. The default is 0:05:00. DRY_STEP is the time step length used for runoff computations (consisting essentially of pollutant buildup) during periods when there is no rainfall and no ponded water. The default is 1:00:00. ROUTING_STEP is the time step length in seconds used for routing flows and water quality constituents through the conveyance system. The default is 20 sec. This can be increased if dynamic wave routing is not used. Fractional values (e.g., 2.5) are permissible as are values entered in hours:minutes:seconds format. LENGTHENING_STEP is a time step, in seconds, used to lengthen conduits under dynamic wave routing, so that they meet the Courant stability criterion under full-flow conditions (i.e., the travel time of a wave will not be smaller than the specified conduit lengthening time step). As this value is decreased, fewer conduits will require lengthening. A value of 0 (the default) means that no conduits will be lengthened. VARIABLE_STEP is a safety factor applied to a variable time step computed for each time period under dynamic wave flow routing. The variable time step is computed so as to satisfy the Courant stability criterion for each conduit and yet not exceed the ROUTING_STEP value. If the safety factor is 0 (the default), then no variable time step is used. MINIMUM_STEP is the smallest time step allowed when variable time steps are used for dynamic wave flow routing. The default value is 0.5 seconds. INERTIAL_DAMPING indicates how the inertial terms in the Saint Venant momentum equation will be handled under dynamic wave flow routing. Choosing NONE maintains these terms at their full value under all conditions. Selecting PARTIAL (the default) will reduce the terms as flow comes closer to being critical (and ignores them when flow is supercritical). Choosing FULL will drop the terms altogether. NORMAL_FLOW_LIMITED specifies which condition is checked to determine if flow in a conduit is supercritical and should thus be limited to the normal flow. Use SLOPE to check if the water surface slope is greater than the conduit slope, FROUDE to check if the Froude number is greater than 1.0, or BOTH to check both conditions. The default is BOTH. SURCHARGE_METHOD selects which method will be used to handle surcharge conditions. The EXTRAN option uses a variation of the Surcharge Algorithm from previous versions of SWMM to update nodal heads when all connecting links become full. The SLOT option uses a Preissmann Slot to add a small amount of virtual top surface width to full flowing pipes so that SWMM's normal procedure for updating nodal heads can continue to be used. The default is EXTRAN. OpenSWMM adds two further methods: DYNAMIC_SLOT, a dynamic Preissmann slot whose pressure-wave celerity is set directly by the modeler (see the Hydraulics Reference Manual, Section 3.3.9, and its DPS_CELERITY, DPS_ALPHA and DPS_DECAY_TIME keywords), and TPA, an experimental two-component pressure approach that lets a sealed full pipe carry sub-atmospheric pressure (Hydraulics Reference Manual, Section 3.3.11). MIN_SURFAREA is a minimum surface area used at nodes when computing changes in water depth under dynamic wave routing. If 0 is entered, then the default value of 12.566 ft2 (1.167 m2) (i.e., the area of a 4-ft diameter manhole) is used. MIN_SLOPE is the minimum value allowed for a conduit’s slope (%). If zero (the default) then no minimum is imposed (although SWMM uses a lower limit on elevation drop of 0.001 ft (0.00035 m) when computing a conduit slope). MAX_TRIALS is the maximum number of trials allowed during a time step to reach convergence when updating hydraulic heads at the conveyance system’s nodes. The default value is 8. HEAD_TOLERANCE is the difference in computed head at each node between successive trials below which the flow solution for the current time step is assumed to have converged. The default tolerance is 0.005 ft (0.0015 m). THREADS is the number of parallel computing threads to use for dynamic wave flow routing on machines equipped with multi-core processors. The default is 1.
New in OpenSWMM v6:
CRS specifies a Coordinate Reference System for the model geometry, given as an EPSG code (e.g. EPSG:4326) or a PROJ string. This value is stored in SimulationOptions::crs and is available through the C API via swmm_spatial_get_crs(). When a CRS is set, all coordinate and polygon data in the [COORDINATES], [VERTICES], and [POLYGONS] sections are assumed to be in that reference system.
TPA_CELERITY is the acoustic wave celerity, in project length units per second, used by SURCHARGE_METHOD TPA to size its constant-width slot. The default is 100. See the Hydraulics Reference Manual, Section 3.3.11.
FV_PRESSURE_CLOSURE selects the pressurization closure of the finite-volume solver (FLOW_ROUTING FV): SLOT (the default, the standard Preissmann slot) or TPA (experimental — the two-component pressure approach, which can represent sub-atmospheric pressure in sealed full pipes). Under TPA the existing FV_SLOT_CELERITY value doubles as the acoustic celerity. See the Hydraulics Reference Manual, Section 8.4.5.
UNSTEADY_FRICTION enables an unsteady (Vítkovský-type) friction term in both the dynamic wave and finite-volume solvers: NONE (the default, bit-identical to earlier releases) or VITKOVSKY. UF_K3 is its Brunone-type coefficient k3, used only when the method is not NONE; the default is 0.015 and the calibrated range reported in the literature is 0.005–0.020. See the Hydraulics Reference Manual, Sections 3.3.12 and 8.5.4.
REPORT_SIGNED_HEADS controls how nodal heads are written to the binary output file: NO (the default) keeps the legacy convention, bit-identical to earlier releases, in which the head is rebuilt from a depth floored at zero; YES writes the true signed piezometric head in the HEAD field — required to observe sub-atmospheric heads produced by the TPA closures — while the DEPTH field stays floored either way. Applies to both solvers.
Any option keyword not recognized by the parser is stored in an extension-options map as a key–value string pair (the key is upper-cased). A non-fatal warning is issued for each unrecognised key. Extension options can be queried at runtime with swmm_options_get_ext() and set with swmm_options_set_ext(). This allows plugins and coupled models to receive configuration through the [OPTIONS] section.
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 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. 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.
Purpose: Identifies optional interface files used or saved by a run.
Formats: USE / SAVE RAINFALL Fname
USE / SAVE RUNOFF Fname
USE / SAVE HOTSTART Fname
USE / SAVE RDII Fname USE INFLOWS Fname SAVE OUTFLOWS Fname
Parameters: Fname is the name of an interface file.
Remarks: Refer to Section 11.7 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). 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.
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 Section 11.3. 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.
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.
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 Section 11.4. 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.
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.
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.
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).
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).
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
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”
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.
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).
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
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.
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)
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).
Remarks: 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.
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.
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.
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.
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.
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 Section 3.2 for a description of the different types of pumps available.
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).
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.
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).
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.
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.
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.
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 Section 3.3.7 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
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.
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.
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.
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).
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.
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.
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.
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.
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.
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
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
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.
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).
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
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 Section 3.2 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
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
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
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
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
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.
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.
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:
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.
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.
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
1.13.2