Runtime Forcing API

Collaboration diagram for Runtime Forcing API:

Functions
SWMM_ENGINE_API int	swmm_forcing_node_lat_inflow (SWMM_Engine engine, int idx, double value, int mode, int persist)
	Force a lateral inflow at a node.
SWMM_ENGINE_API int	swmm_forcing_node_head_boundary (SWMM_Engine engine, int idx, double value, int mode, int persist)
	Force a head boundary at an outfall node.
SWMM_ENGINE_API int	swmm_forcing_node_quality (SWMM_Engine engine, int node_idx, int pollutant_idx, double mass_rate, int mode, int persist)
	Force a quality mass flux at a node.
SWMM_ENGINE_API int	swmm_forcing_link_flow (SWMM_Engine engine, int idx, double value, int mode, int persist)
	Force a flow in a link.
SWMM_ENGINE_API int	swmm_forcing_link_setting (SWMM_Engine engine, int idx, double value, int mode, int persist)
	Force a control setting on a link (pump, orifice, weir, outlet).
SWMM_ENGINE_API int	swmm_forcing_subcatch_rainfall (SWMM_Engine engine, int idx, double value, int mode, int persist)
	Force rainfall on a subcatchment (bypasses gage lookup).
SWMM_ENGINE_API int	swmm_forcing_subcatch_evap (SWMM_Engine engine, int idx, double value, int mode, int persist)
	Force an evaporation rate on a subcatchment.
SWMM_ENGINE_API int	swmm_forcing_gage_rainfall (SWMM_Engine engine, int idx, double value, int mode, int persist)
	Force rainfall on a rain gage (affects all linked subcatchments).
SWMM_ENGINE_API int	swmm_forcing_clear (SWMM_Engine engine, int type, int idx)
	Clear forcing on a specific element and channel.
SWMM_ENGINE_API int	swmm_forcing_clear_all (SWMM_Engine engine)
	Clear ALL forcings on ALL elements.

Detailed Description

Author

Caleb Buahin caleb.nosp@m..bua.nosp@m.hin@g.nosp@m.mail.nosp@m..com

Copyright

Copyright (c) 2026 HydroCouple. All rights reserved.

License\n MIT License

Function Documentation

swmm_forcing_clear()

SWMM_ENGINE_API int swmm_forcing_clear	(	SWMM_Engine	engine,
		int	type,
		int	idx
	)

Clear forcing on a specific element and channel.

Parameters

engine	Engine handle.
type	Forcing channel (SWMM_ForcingType enum).
idx	Element index within that channel.

Returns

SWMM_OK or error code.

swmm_forcing_clear_all()

SWMM_ENGINE_API int swmm_forcing_clear_all

(

SWMM_Engine

engine

)

Clear ALL forcings on ALL elements.

Parameters

engine

Engine handle.

Returns

SWMM_OK or error code.

swmm_forcing_gage_rainfall()

SWMM_ENGINE_API int swmm_forcing_gage_rainfall	(	SWMM_Engine	engine,
		int	idx,
		double	value,
		int	mode,
		int	persist
	)

Force rainfall on a rain gage (affects all linked subcatchments).

Parameters

engine	Engine handle.
idx	Gage index.
value	Rainfall rate (in/hr for US, mm/hr for SI).
mode	SWMM_FORCING_OVERRIDE or SWMM_FORCING_ADD.
persist	SWMM_FORCING_RESET or SWMM_FORCING_PERSIST.

Returns

SWMM_OK or error code.

swmm_forcing_link_flow()

SWMM_ENGINE_API int swmm_forcing_link_flow	(	SWMM_Engine	engine,
		int	idx,
		double	value,
		int	mode,
		int	persist
	)

Force a flow in a link.

Parameters

engine	Engine handle.
idx	Link index.
value	Flow rate (CFS for US, CMS for SI).
mode	SWMM_FORCING_OVERRIDE or SWMM_FORCING_ADD.
persist	SWMM_FORCING_RESET or SWMM_FORCING_PERSIST.

Returns

SWMM_OK or error code.

swmm_forcing_link_setting()

SWMM_ENGINE_API int swmm_forcing_link_setting	(	SWMM_Engine	engine,
		int	idx,
		double	value,
		int	mode,
		int	persist
	)

Force a control setting on a link (pump, orifice, weir, outlet).

Parameters

engine	Engine handle.
idx	Link index.
value	Setting value (0.0–1.0 for fraction open; pump speed).
mode	SWMM_FORCING_OVERRIDE or SWMM_FORCING_ADD.
persist	SWMM_FORCING_RESET or SWMM_FORCING_PERSIST.

Returns

SWMM_OK or error code.

swmm_forcing_node_head_boundary()

SWMM_ENGINE_API int swmm_forcing_node_head_boundary	(	SWMM_Engine	engine,
		int	idx,
		double	value,
		int	mode,
		int	persist
	)

Force a head boundary at an outfall node.

Parameters

engine	Engine handle.
idx	Node index (must be OUTFALL type).
value	Boundary head (ft for US, m for SI).
mode	SWMM_FORCING_OVERRIDE (only valid mode for head boundary).
persist	SWMM_FORCING_RESET or SWMM_FORCING_PERSIST.

Returns

SWMM_OK or error code.

swmm_forcing_node_lat_inflow()

SWMM_ENGINE_API int swmm_forcing_node_lat_inflow	(	SWMM_Engine	engine,
		int	idx,
		double	value,
		int	mode,
		int	persist
	)

Force a lateral inflow at a node.

Parameters

engine	Engine handle.
idx	Node index.
value	Lateral inflow rate (CFS for US, CMS for SI).
mode	SWMM_FORCING_OVERRIDE or SWMM_FORCING_ADD.
persist	SWMM_FORCING_RESET or SWMM_FORCING_PERSIST.

Returns

SWMM_OK or error code.

swmm_forcing_node_quality()

SWMM_ENGINE_API int swmm_forcing_node_quality	(	SWMM_Engine	engine,
		int	node_idx,
		int	pollutant_idx,
		double	mass_rate,
		int	mode,
		int	persist
	)

Force a quality mass flux at a node.

Parameters

engine	Engine handle.
node_idx	Node index.
pollutant_idx	Pollutant index.
mass_rate	Mass injection rate (mass/sec in concentration units × CFS).
mode	SWMM_FORCING_OVERRIDE or SWMM_FORCING_ADD.
persist	SWMM_FORCING_RESET or SWMM_FORCING_PERSIST.

Returns

SWMM_OK or error code.

swmm_forcing_subcatch_evap()

SWMM_ENGINE_API int swmm_forcing_subcatch_evap	(	SWMM_Engine	engine,
		int	idx,
		double	value,
		int	mode,
		int	persist
	)

Force an evaporation rate on a subcatchment.

Parameters

engine	Engine handle.
idx	Subcatchment index.
value	Evaporation rate (ft/sec internal units).
mode	SWMM_FORCING_OVERRIDE or SWMM_FORCING_ADD.
persist	SWMM_FORCING_RESET or SWMM_FORCING_PERSIST.

Returns

SWMM_OK or error code.

swmm_forcing_subcatch_rainfall()

SWMM_ENGINE_API int swmm_forcing_subcatch_rainfall	(	SWMM_Engine	engine,
		int	idx,
		double	value,
		int	mode,
		int	persist
	)

Force rainfall on a subcatchment (bypasses gage lookup).

Parameters

engine	Engine handle.
idx	Subcatchment index.
value	Rainfall rate (in/hr for US, mm/hr for SI).
mode	SWMM_FORCING_OVERRIDE or SWMM_FORCING_ADD.
persist	SWMM_FORCING_RESET or SWMM_FORCING_PERSIST.

Returns

SWMM_OK or error code.