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 … Read the rest
A Harvard study warned that AI intensifies work. Here’s what that looks like when the work is stormwater modeling and the worker has half a century of hydraulic knowledge to unleash.
Updated July 2026.
If you’re serious about modeling, you’ll need to understand how the engine solves differential equations sooner or later. So the next time the engine does something strange, you’ll know what to look for.
Most people, I believe, are like me in that they cannot derive their intuition from equations; it … Read the rest
The SWMM3 Weir Test File: A Historical Reference for Modern Hydraulic Modeling
This test file holds special historical significance in the development of stormwater modeling. Originally published in the 1981 EXTRAN 3 manual by CDM (now CDM Smith), it was specifically designed to validate orifice calculations in hydraulic networks. The … Read the rest
The SWMM3 or Extran3 Side Outlet Orifice Test File: A Historical Reference for Modern Hydraulic Modeling
This is a story about one inp file. It shows the continuity in stormwater modeling from 1980 to 2025 onwards. It is about Example 5 from the 1981 Extran Manual. This compact test case, … Read the rest
The SWMM3 or Extran3 Type 1 Pump Test File: A Historical Reference for Modern Hydraulic Modeling
This is a story about one inp file. It shows the continuity in stormwater modeling from 1980 to 2025 onwards. It is about Example 6 from the 1981 Extran Manual. This compact test case, … Read the rest
The SWMM3 or Extran3 Type 2 Pump Test File: A Historical Reference for Modern Hydraulic Modeling
This is a story about one inp file. It shows the continuity in stormwater modeling from 1980 to 2025 onwards. It is about Example 7 from the 1981 Extran Manual. This compact test case, … Read the rest
Autodesk Water Technologist for Storm Sewer and Flood | Expert in ICM InfoWorks ICM SWMM/Ruby | 18 Years at Innovyze/Autodesk | 52 Years with EPASWMM TAC for CIMM.ORG … Read the rest
This is a story about two inp files. It shows the continuity in stormwater modeling from 1980 to 2025 onwards. It is about Extran1 (free outfall) and Extran 2 (fixed backwater with a tide gate) from the 1981 Extran Manual. This compact test case, born in the era of punch … Read the rest
The SWMM3 Orifice Test File: A Historical Reference for Modern Hydraulic Modeling
This test file holds special historical significance in the development of stormwater modeling. Originally published in the 1981 EXTRAN 3 manual by CDM (now CDM Smith), it was specifically designed to validate orifice calculations in hydraulic networks. The … Read the rest
Diamond Village is one of the University of Florida’s long-standing graduate and family housing communities, known for its close-knit atmosphere and the unique civic structure that encourages resident leadership. Over the decades, Diamond Village has … Read the rest
A collection of various versions of SWMM 3 and 4. WCH_2004 is the last version developed by Wayne Huber at OSU in 2004 before the 1st SWMM5 release
and code for SWMM4.99 by CDM Pittsburgh (as of 2004)
A note from the past, the SWMM3 and SWMM4 Acknowledgments from their respective manuals for the sake of posterity and in thanks for all of their past efforts.
Maintenance and updating of the EPA SWMM has been continuous since its
inception in 1969-70.
Over the many intervening years … Read the rest
This is part of the #Inside_#SWMM5 series of blogs and is intended as a visual aid and code developer for the Storm Water Management Model Reference Manuals on https://www.epa.gov/water-research/storm-water-management-model-swmm I always think images (and some words) are best at explaining the internal working of code. I do encourage you to … Read the rest
Here is a graphical view of the nonlinear runoff processes in InfoSWMM and SWMM5:
1. Three runoff surfaces
a. Impervious with Depression Storage
b. Pervious
c. Impervious without Depression Storage
2. Slope (same for all runoff surfaces)
3. Width or the Dimension of the Subcatchment (same for all runoff surfaces)… Read the rest
Huber Nato Water Quality Paper about Water Quality in SWMM4
This is just so I can find this using Google Search in the Future
SWMM 3 Manual and PDF File