EPA's Storm Water Management Model (SWMM) is used throughout the world for planning, analysis, and design related to stormwater runoff, combined and sanitary sewers, and other drainage systems. It can be used to evaluate gray infrastructure stormwater control strategies, such as pipes and storm drains, and is a useful tool for creating cost-effective green/gray hybrid stormwater control solutions. SWMM was developed to help support local, state, and national stormwater management objectives to reduce runoff through infiltration and retention, and help to reduce discharges that cause impairment of waterbodies.

SWMM is a Windows-based desktop program. It is open source public software and is free for use worldwide. SWMM 5 was produced in a joint development effort with CDM Smith Inc., a global consulting, engineering, construction, and operations firm.

Date

Description

Self-Extracting Installation Program for SWMM 5.2.4 (32-bit) (exe)

08/07/2023

Self-Extracting Installation Program for SWMM 5.2.4 (64-bit) (exe)

Date

Description

SWMM 5.1 User's Manual (pdf)

Open Source SWMM: Adaptive Quality Management (pdf)

Self-Extracting Installation Program for SWMM 5.2.1. (32-bit) (exe)

Utility for converting SWMM 4 data files to SWMM 5 files (exe)

SWMM is used for single event or long-term simulations of water runoff quantity and quality in primarily urban areas—although there are also many applications that can be used for drainage systems in non-urban areas. SWMM provides an integrated environment for editing study area input data, running hydrologic, hydraulic and water quality simulations, and viewing the results in a variety of formats. These include color-coded drainage area and conveyance system maps, time series graphs and tables, profile plots, and statistical frequency analyses.

SWMM contains a flexible set of hydraulic modeling capabilities used to route runoff and external inflows through the drainage system network of pipes, channels, storage/treatment units and diversion structures. These include the ability to do the following:

SWMM accounts for various hydrologic processes that produce runoff from urban areas, which include the following:

Spatial variability in all of these processes is achieved by dividing a study area into a collection of smaller, homogeneous sub-catchment areas. Each of the areas contains its own fraction of pervious and impervious sub-areas. Overland flow can be routed between sub-areas, between sub-catchments, or between entry points of a drainage system.

SWMM can estimate the production of pollutant loads associated with stormwater runoff. The following processes can be modeled for any number of user-defined water quality constituents:

SWMM includes a software utility that allows future climate change projections to be incorporated into modeling. The SWMM Climate Adjustment Tool (SWMM-CAT) provides a set of location-specific adjustments derived from World Climate Research Programme global climate change models. SWMM-CAT accepts monthly adjustment factors for climate-related variables that could represent the potential impact of future climate changes.

This SWMM add-in tool will help you create a times series of rainfall intensities for a design storm of a given depth, duration, and return period. You can use from a variety of standard deign storm distributions and use Intensity-Duration-Frequency curve information if available. The result can be copied or saved for later use within the EPA Storm Water Management Model (SWMM). 

Access the Dstorm Tool

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Typical applications of SWMM:

SWMM allows engineers and planners to represent combinations of green infrastructure practices as low impact development (LID) controls to determine their effectiveness in managing runoff. Some of these practices can also provide significant pollutant reduction benefits.

Bioretention Cells (or Bioswales) Bioretention cells are depressions containing vegetation grown in an engineered soil mixture placed above a gravel drainage bed that provide storage, infiltration, and evaporation of both direct rainfall and runoff captured from surrounding areas.

Green Roofs Green roofs are a variation of a bioretention cells that have a soil layer atop a special drainage mat material that conveys excess percolated rainfall off of the roof. They contain vegetation that enable rainfall infiltration and evapotranspiration of stored water.