The engines from 1971 to now, rebuilt and running in your browser.
SWMM began in 1969 to 1971 as an EPA project with Metcalf & Eddy, the University of Florida and Water Resources Engineers. I went to Florida in 1973 to work on it, and I have worked on SWMM itself since 1978, starting with SWMM 2.5.
This page collects that history and the old engines. SWMM 1 and EXTRAN III were rebuilt from their printed program listings, and SWMM 4.4H from its Fortran source, so you can run them in a browser next to SWMM5.
Start here
- History of SWMM 1, 2, 3, 4, 5 to the Year 2015. The versions from 1969 to 2015, and how H2OMap SWMM and InfoSWMM connect to SWMM5.
- SWMM Volume III, User’s Manual, September 1971. The original 1971 user’s manual.
- Reviving 1988 SWMM4 Models with AI. Bringing SWMM4 input files forward to SWMM5.
Try a tool
- SWMM 1 Engine. The 1971 SWMM 1 Runoff engine rebuilt as WebAssembly, with a SWMM5 file import.
- EXTRAN III, Alive Again. EXTRAN III rebuilt from the 1981 listing and run in the browser.
- SWMM 4.4H Engine. SWMM 4.4H in the browser, with a SWMM5 file import.
More apps on this topic
- The SWMM 1 Book. A short book on SWMM 1, built from the engine app.
- XP to SWMM5. Convert XP-SWMM .xp files to SWMM5.
- Visual SWMM at CHI 1999. Visual SWMM as presented at the 1999 CHI conference.
- Water Modeling to the Year 3000. A timeline of water modeling, past and imagined, out to the year 3000.
- CDM-SWMM4. A batch runner for SWMM4 models.
Work through an example
- The SWMM3 Orifice Test File. A historical test file to run in SWMM5 and ICM.
- Extran1 and Extran2 from the Extran Manual. The two classic EXTRAN examples as modern files.
- SWMM3 Weir Extran4 Test File. A weir test that has run in every SWMM since SWMM3.
- AI Time Travel to Convert SWMM4 to SWMM5 Files. A worked SWMM4-to-SWMM5 conversion.
Code and automation
- SWMMEnablement/WCH_2004_SWMM44H. The SWMM 4.4H Fortran source.
- SWMMEnablement/cdm-swmm4. Source for the SWMM4 batch runner.
- dickinsonre/SwmmHistory. SWMM history material.
Recently added
- SWMM 1 Engine. October 2026.
- EXTRAN III, Alive Again. October 2026.
- SWMM 4.4H Engine. October 2026.
Explore the archive
- SWMM3 posts. Everything tagged SWMM3.
- SWMM 5.1 Update History. Every SWMM 5.1 release up to 5.1.013.
- File Formats (older topic page). Readers and converters for older file formats.
Explore the six topics
- SWMM History: SWMM1 to SWMM6 (this page)
- Inside SWMM5
- SWMM5 and ICM InfoWorks
- ICM InfoWorks and SWMM6
- Inside SWMM6
- Comparing Models with AI
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Use of AI: Claude (Anthropic) drafted this page in November 2026. It picked the entries from my swmm5.org posts, Netlify apps and GitHub repositories and wrote the one-line descriptions. I chose the six topics and the layout.