What you'll do

Look up a numbered message that a run produced, and find out which of the two numbering systems SWMMVis shows you it belongs to.

A failed run is reported in the simulation status panel as ERROR [n] ERROR mmm: … — the bracketed n is an API error code and the mmm inside the message is an engine error. They are different catalogues; both are below.

Where to find it

Message Logs panel, the simulation status panel while a run is active, and the .rpt status report opened from Analysis → Report. See 20 — Running a Simulation and 24 — Tabular Results and Reports.

For what to do about the common ones, see A5 — Troubleshooting, which carries remediation advice for the messages users actually hit. This appendix is the complete index, not a troubleshooting guide.

Step-by-step

How this page is maintained

This page is generated by scripts/gen_error_catalogue.py from the engine's own enumerations — do not edit it by hand.


Source	`openswmm.engine` `src/engine/core/ErrorCodes.hpp`
Engine revision	`swmm6_rel` @ `62644090`
Generated	2026-09-19
Codes	128 Engine errors · 21 Engine warnings · 15 API error codes · 7 API warning codes

scripts/gen_error_catalogue.py --check fails when the engine has gained a code this page does not list; it runs in CI against the engine checkout that build_and_test.yml already makes.

Engine errors

Reported by the engine and shown in the Message Logs and the status report. s stands for the object name the engine names in the message.

ERROR	Symbol	Message
101	`ERR_MEMORY`	memory allocation error
103	`ERR_KINWAVE`	cannot solve KW equations for Link s
105	`ERR_ODE_SOLVER`	cannot open ODE solver
107	`ERR_TIMESTEP`	cannot compute a valid time step
108	`ERR_SUBCATCH_OUTLET`	ambiguous outlet ID name for Subcatchment s
109	`ERR_AQUIFER_PARAMS`	invalid parameter values for Aquifer s
110	`ERR_GROUND_ELEV`	ground elevation is below water table for Subcatchment s
111	`ERR_LENGTH`	invalid length for Conduit s
112	`ERR_ELEV_DROP`	elevation drop exceeds length for Conduit s
113	`ERR_ROUGHNESS`	invalid roughness for Conduit s
114	`ERR_BARRELS`	invalid number of barrels for Conduit s
115	`ERR_SLOPE`	adverse slope for Conduit s
117	`ERR_NO_XSECT`	no cross section defined for Link s
119	`ERR_XSECT`	invalid cross section for Link s
121	`ERR_NO_CURVE`	missing or invalid pump curve assigned to Pump s
122	`ERR_PUMP_LIMITS`	startup depth not higher than shutoff depth for Pump s
131	`ERR_LOOP`	links form cyclic loops in the drainage system
133	`ERR_MULTI_OUTLET`	Node s has more than one outlet link
134	`ERR_DUMMY_LINK`	Node s has illegal DUMMY link connections
135	`ERR_DIVIDER`	Divider s does not have two outlet links
136	`ERR_DIVIDER_LINK`	Divider s has invalid diversion link
137	`ERR_WEIR_DIVIDER`	Weir Divider s has invalid parameters
138	`ERR_NODE_DEPTH`	Node s has initial depth greater than maximum depth
139	`ERR_REGULATOR`	Regulator s is the outlet of a non-storage node
140	`ERR_STORAGE_VOLUME`	Storage node s has negative volume at full depth
141	`ERR_OUTFALL`	Outfall s has more than 1 inlet link or an outlet link
143	`ERR_REGULATOR_SHAPE`	Regulator s has invalid cross-section shape
145	`ERR_NO_OUTLETS`	Drainage system has no acceptable outlet nodes
151	`ERR_UNITHYD_TIMES`	a Unit Hydrograph in set s has invalid time base
153	`ERR_UNITHYD_RATIOS`	a Unit Hydrograph in set s has invalid response ratios
155	`ERR_RDII_AREA`	invalid sewer area for RDII at node s
156	`ERR_RAIN_FILE_CONFLICT`	ambiguous station ID for Rain Gage s
157	`ERR_RAIN_GAGE_FORMAT`	inconsistent rainfall format for Rain Gage s
158	`ERR_RAIN_GAGE_TSERIES`	time series for Rain Gage s is also used by another object
159	`ERR_RAIN_GAGE_INTERVAL`	recording interval greater than time series interval for Rain Gage s
161	`ERR_CYCLIC_TREATMENT`	cyclic dependency in treatment functions at node s
171	`ERR_CURVE_SEQUENCE`	Curve s has invalid or out of sequence data
173	`ERR_TIMESERIES_SEQUENCE`	Time Series s has its data out of sequence
181	`ERR_SNOWMELT_PARAMS`	invalid Snow Melt Climatology parameters
182	`ERR_SNOWPACK_PARAMS`	invalid parameters for Snow Pack s
183	`ERR_LID_TYPE`	no type specified for LID s
184	`ERR_LID_LAYER`	missing layer for LID s
185	`ERR_LID_PARAMS`	invalid parameter value for LID s
187	`ERR_LID_AREAS`	LID area exceeds total area for Subcatchment s
188	`ERR_LID_CAPTURE_AREA`	LID capture area exceeds total impervious area for Subcatchment s
191	`ERR_START_DATE`	simulation start date comes after ending date
193	`ERR_REPORT_DATE`	report start date comes after ending date
195	`ERR_REPORT_STEP`	reporting time step or duration is less than routing time step
200	`ERR_INPUT`	one or more errors in input file
201	`ERR_INPUT_LINE`	too many characters in input line
203	`ERR_ITEMS`	too few items
205	`ERR_KEYWORD`	invalid keyword s
207	`ERR_DUP_NAME`	duplicate ID name s
209	`ERR_NAME`	undefined object s
211	`ERR_NUMBER`	invalid number s
213	`ERR_DATETIME`	invalid date/time s
217	`ERR_CONTROL_RULE`	control rule clause invalid or out of sequence
219	`ERR_TRANSECT_UNKNOWN`	data provided for unidentified transect
221	`ERR_TRANSECT_SEQUENCE`	transect station out of sequence
223	`ERR_TRANSECT_TOO_FEW`	Transect s has too few stations
225	`ERR_TRANSECT_TOO_MANY`	Transect s has too many stations
227	`ERR_TRANSECT_MANNING`	Transect s has no Manning's N
229	`ERR_TRANSECT_OVERBANK`	Transect s has invalid overbank locations
231	`ERR_TRANSECT_NO_DEPTH`	Transect s has no depth
233	`ERR_MATH_EXPR`	invalid math expression
235	`ERR_INFILTRATION`	invalid infiltration parameters
301	`ERR_FILE_NAME`	files share same names
303	`ERR_INP_FILE`	cannot open input file
305	`ERR_RPT_FILE`	cannot open report file
307	`ERR_OUT_FILE`	cannot open binary results file
308	`ERR_OUT_SIZE`	output will exceed maximum file size
309	`ERR_OUT_WRITE`	error writing to binary results file
311	`ERR_OUT_READ`	error reading from binary results file
313	`ERR_RAIN_IFACE_SCRATCH`	cannot open scratch rainfall interface file
315	`ERR_RAIN_IFACE`	cannot open rainfall interface file s
317	`ERR_RAIN_FILE_OPEN`	cannot open rainfall data file s
318	`ERR_RAIN_FILE_SEQUENCE`	line is out of sequence in rainfall data file s
319	`ERR_RAIN_FILE_FORMAT`	unknown format for rainfall data file s
320	`ERR_RAIN_IFACE_FORMAT`	invalid format for rainfall interface file
321	`ERR_RAIN_IFACE_GAGE`	no data in rainfall interface file for gage s
323	`ERR_RUNOFF_IFACE`	cannot open runoff interface file s
325	`ERR_RUNOFF_IFACE_COMPAT`	incompatible data found in runoff interface file
327	`ERR_RUNOFF_IFACE_EOF`	attempting to read beyond end of runoff interface file
329	`ERR_RUNOFF_IFACE_READ`	error in reading from runoff interface file
331	`ERR_HOTSTART_FILE`	cannot open hot start interface file s
333	`ERR_HOTSTART_COMPAT`	incompatible data found in hot start interface file
335	`ERR_HOTSTART_READ`	error in reading from hot start interface file
336	`ERR_NO_CLIMATE_FILE`	no climate file specified for evaporation and/or wind speed
337	`ERR_CLIMATE_FILE_OPEN`	cannot open climate file s
338	`ERR_CLIMATE_FILE_READ`	error in reading from climate file s
339	`ERR_CLIMATE_FILE_EOF`	attempt to read beyond end of climate file s
341	`ERR_RDII_IFACE_SCRATCH`	cannot open scratch RDII interface file
343	`ERR_RDII_IFACE`	cannot open RDII interface file s
345	`ERR_RDII_IFACE_FORMAT`	invalid format for RDII interface file
351	`ERR_ROUTING_IFACE`	cannot open routing interface file s
353	`ERR_ROUTING_IFACE_FORMAT`	invalid format for routing interface file s
355	`ERR_ROUTING_IFACE_NAMES`	mis-matched names in routing interface file s
357	`ERR_ROUTING_IFACE_SAME`	inflows and outflows interface files have same name
361	`ERR_TABLE_FILE_OPEN`	could not open external file used for Time Series s
363	`ERR_TABLE_FILE_READ`	invalid data in external file used for Time Series s
500	`ERR_SYSTEM`	System exception thrown
501	`ERR_API_NOT_OPENED`	project not opened
502	`ERR_API_NOT_STARTED`	simulation not started
503	`ERR_API_NOT_ENDED`	simulation not ended
504	`ERR_API_OBJECT_TYPE`	invalid object type
505	`ERR_API_OBJECT_INDEX`	invalid object index
506	`ERR_API_OBJECT_NAME`	invalid object name
507	`ERR_API_PROPERTY_TYPE`	invalid property type
508	`ERR_API_PROPERTY_VALUE`	invalid property value
509	`ERR_API_TIME_PERIOD`	invalid time period
601	`ERR_TIMESERIES_EMPTY`	Time Series s has no data
603	`ERR_TIMESERIES_NAN`	Time Series s contains NaN or Inf values
605	`ERR_TABLE_COL_MISMATCH`	column count mismatch in data for s
607	`ERR_GAGE_TSERIES_NOTFOUND`	Rain Gage s references unknown time series
609	`ERR_VJ_LINK_COUNT`	Virtual Junction s must connect exactly two conduits
611	`ERR_VJ_XSECT_MISMATCH`	Virtual Junction s connects conduits with different cross sections
613	`ERR_VJ_OFFSET`	Virtual Junction s has a conduit with a nonzero offset
615	`ERR_VJ_INVERT_MISMATCH`	Virtual Junction s conduit inverts do not agree at the node
617	`ERR_VJ_LATERAL_INFLOW`	Virtual Junction s cannot be coupled to a 2D surface mesh (point laterals are allowed)
619	`ERR_VJ_ROUTING_MODEL`	Virtual Junction s requires DYNWAVE or FV flow routing
621	`ERR_VJ_EXTRA_TOKENS`	too many items for Virtual Junction s
623	`ERR_IJ_NOT_STREET`	Inlet Junction s must connect two STREET conduits (or RECT_OPEN/TRAPEZOIDAL for drop inlets)
625	`ERR_IJ_DESIGN`	Inlet Junction s references an unknown inlet design
627	`ERR_IJ_CAPTURE_NODE`	Inlet Junction s has an invalid capture node (missing, itself, or virtual)
629	`ERR_IJ_USAGE_ON_PAIR`	Inlet Junction s conduit also carries an [INLET_USAGE] entry
631	`ERR_IJ_EXTRA_TOKENS`	too many items for Inlet Junction s
633	`ERR_IJ_NO_USAGE`	Inlet Junction s has no inlet design assigned
635	`ERR_INLET_USAGE_SHAPE`	Inlet s cannot be used with the cross section of s

Engine warnings

The run continues. Warnings are worth reading — several of them mean the engine silently changed something you asked for.

WARNING	Symbol	Message
1	`WARN_WET_STEP_REDUCED`	wet weather time step reduced to recording interval for Rain Gage s
2	`WARN_MAX_DEPTH_INCREASED`	maximum depth increased for Node s
3	`WARN_NEGATIVE_OFFSET`	negative offset ignored for Link s
4	`WARN_MIN_ELEV_DROP`	minimum elevation drop used for Conduit s
5	`WARN_MIN_SLOPE`	minimum slope used for Conduit s
6	`WARN_DRY_STEP_INCREASED`	dry weather time step increased to the wet weather time step
7	`WARN_ROUTING_STEP_REDUCED`	routing time step reduced to the wet weather time step
8	`WARN_ELEV_DROP_EXCEEDS`	elevation drop exceeds length for Conduit s
9	`WARN_GAGE_INTERVAL`	time series interval greater than recording interval for Rain Gage s
10	`WARN_REGULATOR_CREST_LOW`	crest elevation is below downstream invert for regulator Link s
11	`WARN_CONTROL_RULE_ATTR`	non-matching attributes in Control Rule s
12	`WARN_INLET_REMOVED`	inlet removed due to unsupported shape for Conduit s
13	`WARN_UH_PARAMS_REPEATED`	parameters for same month provided more than once for Unit Hydrograph s
101	`WARN_TIMESERIES_DUPLICATE_X`	Time Series s has duplicate x values
102	`WARN_BOUNDARY_OVERLAP`	boundary regions overlap for s
103	`WARN_FILES_SLOT_UNSUPPORTED`	[FILES] s is not supported and was ignored
104	`WARN_2D_OPTION_RETIRED`	[2D_OPTIONS] s retired with CVODE/ARKODE and was ignored
105	`WARN_FV_OPTION_INERT`	s has no effect under FLOW_ROUTING FV
106	`WARN_DW_OPTION_UNDER_FV`	s is a dynamic wave option and does not apply under FLOW_ROUTING FV
107	`WARN_RAIN_CSV_ROWS_SKIPPED`	unreadable row(s) skipped in rainfall CSV for Rain Gage s
108	`WARN_FV_SLOT_CAP`	slot width cap (5% of top width) overrides FV_SLOT_CELERITY for s

API error codes

The bracketed number in ERROR [n] … in the simulation status panel. These come from the C API layer; the engine error above is the cause.

API ERROR	Symbol	Message
1	`CFFI_ERR_NOMEM`	memory allocation error
2	`CFFI_ERR_INPFILE`	cannot open input file
3	`CFFI_ERR_RPTFILE`	cannot open report file
4	`CFFI_ERR_OUTFILE`	cannot open output file
5	`CFFI_ERR_PARSE`	input parsing error
6	`CFFI_ERR_LIFECYCLE`	invalid engine lifecycle state transition
7	`CFFI_ERR_BADHANDLE`	invalid engine handle
8	`CFFI_ERR_BADINDEX`	invalid object index
9	`CFFI_ERR_BADPARAM`	invalid parameter value
10	`CFFI_ERR_PLUGIN`	plugin initialization or execution error
11	`CFFI_ERR_IO`	file I/O error
12	`CFFI_ERR_HOTSTART`	hot start file error
13	`CFFI_ERR_CRS`	coordinate reference system error
14	`CFFI_ERR_NUMERICAL`	numerical solver error
99	`CFFI_ERR_INTERNAL`	internal engine error

API warning codes

The bracketed number of a non-fatal API condition.

API WARNING	Symbol	Message
1	`CFFI_WARN_HOTSTART_MISSING`	hot start file not found, cold start used
2	`CFFI_WARN_UNKNOWN_SECTION`	unknown section in input file
3	`CFFI_WARN_UNKNOWN_OPTION`	unknown option in input file
4	`CFFI_WARN_DEPRECATED_KW`	deprecated keyword used
5	`CFFI_WARN_PLUGIN_INIT`	plugin initialization warning
6	`CFFI_WARN_NUMERICAL`	numerical approximation used
7	`CFFI_WARN_STABILITY_LIMIT`	time step reduced for stability

Tips and gotchas

Two numbers, two catalogues. ERROR [1] ERROR 141: … is API error 1 reporting engine error 141. Look up the inner number first — it is the one that names the object and the cause.
**s is a placeholder.** The engine substitutes the offending object's ID, so the message you see names the junction, conduit or subcatchment.
A warning is not a failure, but it may have changed your model. Several warnings report that the engine substituted a value for one it could not use.
A code missing here means the page is stale, not that the code is invalid. Regenerate with scripts/gen_error_catalogue.py.