EPA SWMM

free (public domain) Engineer & Analyze

Free, public-domain stormwater, wastewater, and combined sewer system simulation model by the US Environmental Protection Agency -- dynamic hydrology-hydraulic-water quality simulation for single-event or continuous modeling of rainfall-runoff, pipe/channel routing, green infrastructure/LID controls, and pollutant loads; the industry-standard computational engine used worldwide for drainage design, CSO/SSO mitigation, floodplain mapping, and regulatory compliance (NPDES, CMOM, TMDL).

3.4 /5 composite score

C1 5/5 reflects free public-domain licensing, and C2 3/5 reflects the open-source C toolkit plus community Python wrappers rather than a managed vendor API or CLI service. C4 5/5 reflects INP-native workflows with CSV and DXF export, and C5 2/5 reflects a lighter integration surface centered on ArcGIS, QGIS, PCSWMM, AutoCAD, and MicroStation.

Solid

Rubric Scorecard

How we grade →

Criterion	Score	Evidence
Value for the price	5/5	free (public domain), from $0, free tier
Agent Friendliness	3/5	API: SWMM 5 Programmer's Toolkit (C API, DLL with 50+ functions for opening/modifying networks, running simulations, accessing results); open-source C engine on GitHub (USEPA/Stormwater-Management-Model)
Ease of adoption	2/5	desktop-install, steep learning curve
Portability & lock-in	5/5	4 file formats
Interoperability	2/5	5 integrations

Pricing

Modelfree (public domain)

Entry price$0

Free tieryes

Free vieweryes

Trialno

Free tier scopeusable

Visit EPA SWMM →

How we verified this: we checked EPA SWMM against its live site and an independent source — en.wikipedia.org. Nothing on this page is listed from memory. See how we grade. Verified 2026-07-05.

Evidence

File formats

Format	Direction	Support
INP	native	full -- SWMM native .inp input format (industry-standard text format)
CSV	export	full
GIS	import	partial
DXF	export	full

Integrations

ArcGIS (middleware) QGIS (middleware) PCSWMM AutoCAD MicroStation

Adoption

Deploymentdesktop-install

Self-serve signupyes

Learning curvesteep

Sources

Status Changelog

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