The Water Decides
Told in the manner of Isaac Asimov’s science essays
Robert (Bob) Dickinson · SWMM Enablement
App version 1.1 · 17 October 2026
Engines: EPA SWMM 5.2.4 and OpenSWMM 6.0.0-alpha.4 (swmm6_rel 64d517f), both compiled to WebAssembly
Units: US customary (ft, s, cfs)
The SWMM3 Weir Test File: A Historical Reference for Modern Hydraulic Modeling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The SWMM3 or Extran3 Side Outlet Orifice Test File: A Historical Reference for Modern Hydraulic Modeling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The SWMM3 or Extran3 Type 1 Pump Test File: A Historical Reference for Modern Hydraulic Modeling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The SWMM3 or Extran3 Type 2 Pump Test File: A Historical Reference for Modern Hydraulic Modeling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
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STORM WATER MANAGEMENT MODEL
QUALITY ASSURANCE REPORT:
Dynamic Wave Flow Routing
By
Lewis A. Rossman
Water Supply and Water Resources Division
National Risk Management Research Laboratory
Cincinnati, OH 45268
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
DISCLAIMER… Read the rest
As SWMM5 is a link node network, the area of a Storage Node is both the area of the Wet Well and typically ½ the surface area of the connecting links. There is no surface area for the Pump(s) downstream of the Wet Well (Storage) but the area of … Read the rest
Question: How does SWMM5 solve the 1D St Venant Equation in its conceptual Link/Node Network?
Answer: See these graphs of the solved for variables in the solution.
1/ There is also an ArcEngine version of InfoSWMM call InfoSWMM SA. I will SA to show some hidden features of the 1D … Read the rest
Storm Water Management Model User’s Manual Version 5.1EditPreview
United States
Environmental Protection
Agency
EPA/600/R - 14/4 13b
Revised September 2015
www2.epa.gov/ water-research
Office of Research and Development
Water Supply and Water Resources New Engine and GUI Features in InfoSWMM 14.7 which is based on EPA SWMM 5.1.013
More about EPA SWMM 5.1.013 https://swmm5.org/2018/08/15/swmm-5-1-update-history-up-to-swmm-5-1-013/
| Individual subcatchments can be assigned time patterns that adjust depression storage, pervious surface roughness and infiltration capacity on a monthly basis (see Subcatchment |
Flow routing within a conduit link in SWMM is governed by the conservation of mass and momentum equations for gradually varied, unsteady flow (i.e., the Saint Venant flow equations). The SWMM user has a choice on the level of sophistication … Read the rest
| Nodes |
Nodes are points of a conveyance system that connect conveyance links together. There are several different categories of nodes that can be employed:
| · | Junctions |
| · | Outfalls |
| · | Flow Dividers |
| · | Storage Units |
Nodes are also the points where external inflows can enter a drainage system … Read the rest
| Project File |
A SWMM Project File is a plain text file that contains all of the data used to describe a study area and the options used to analyze it. The file is organized into sections, where each section generally corresponds to a particular category of object … Read the rest
| Printing and Copying |
This section describes how to print, copy to the Windows clipboard, or copy to file the contents of the currently active window in the SWMM workspace. This can include the Study Area Map, a graph, a table, or a report.
| · | Selecting a printer |
EPA/600/R - 14/4 13b
Revised September 2015
www2.epa.gov/ water-researchOffice of Research and Development
Water Supply and Water Resources DivisionEPA- 600 /R-14/413b
Revisied September 2015