Storm Water Management Model

The <a href="/facts/United_States_Environmental_Protection_Agency/ghI985SI">United States Environmental Protection Agency</a> (EPA) Storm Water Management Model (SWMM) is a dynamic <a href="/facts/Rainfall/MLqcQEyx">rainfall</a>–<a href="/facts/Surface_runoff/zPxoaA0D">runoff</a>–<a href="/facts/Groundwater/JYM2IDS2">subsurface runoff</a> <a href="/facts/Scientific_modelling/aNyvIyUQ">simulation model</a> used for single-event to long-term (continuous) <a href="/facts/Simulation/Q4QJV1oI">simulation</a> of the surface/subsurface hydrology quantity and <a href="/facts/Water_quality/PcEERmpX">quality</a> from primarily urban/suburban areas.
It can simulate the rainfall-runoff, runoff, <a href="/facts/Evaporation/tgvIlJys">evaporation</a>, <a href="/facts/Infiltration_(hydrology)/p4n7qhVy">infiltration</a> and groundwater connection for roots, streets, grassed areas, rain gardens and ditches and pipes, for example. The hydrology component of SWMM operates on a collection of <a href="/facts/Drainage_basin/lzsx0XJS">subcatchment areas</a> divided into <a href="/facts/Impervious_surface/eN3LN2ks">impervious</a> and pervious areas with and without <a href="/facts/Depression_storage_capacity/nJ9SxpEE">depression</a> storage to predict runoff and <a href="/facts/Pollutant/4f9kmFzq">pollutant</a> loads from precipitation, evaporation and <a href="/facts/Infiltration_(hydrology)/p4n7qhVy">infiltration</a> losses from each of the subcatchment. Besides, low impact development (LID) and best management practice areas on the subcatchment can be modeled to reduce the impervious and pervious runoff. The routing or hydraulics section of SWMM transports this water and possible associated <a href="/facts/Water_quality/PcEERmpX">water quality</a> constituents through a system of closed pipes, open channels, storage/treatment devices, ponds, storages, pumps, orifices, weirs, outlets, outfalls and other regulators.
SWMM tracks the quantity and quality of the flow generated within each subcatchment, and the flow rate, flow depth, and quality of water in each pipe and channel during a simulation period composed of multiple fixed or variable <a href="/facts/Explicit_and_implicit_methods/jnJhWfuh">time steps</a>. The water quality constituents such as <a href="/facts/Total_dissolved_solids/l22EkNSN">water quality constituents</a> can be simulated from buildup on the subcatchments through washoff to a <a href="/facts/Hydraulic/KSIqLovc">hydraulic</a> network with optional first order decay and linked pollutant removal, best management practice and <a href="/facts/Low-impact_development_(Canada/US)/etuQCy65">low-impact development</a> (LID) removal and treatment can be simulated at selected storage nodes. SWMM is one of the <a href="/facts/Hydrology_transport_model/l7DY2NMN">hydrology transport models</a> which the EPA and other agencies have applied widely throughout North America and through consultants and universities throughout the world. The latest update notes and new features can be found on the EPA website in the download section. Recently added in November 2015 were the EPA SWMM 5.1 Hydrology Manual (Volume I) and in 2016 the EPA SWMM 5.1 Hydraulic Manual (Volume II) and EPA SWMM 5.1 Water Quality (including LID Modules) Volume (III) + Errata.

Storm Water Management Model open-in-new

Storm Water Management Model