OpenSWMM Engine Manual

See Authors & Contributors for the full list of authors and contributors.

DISCLAIMER

This software is provided on an "as is" basis and the user assumes responsibility for its use. Although a reasonable effort has been made to assure that the results obtained are correct, the authors are not responsible and assume no liability whatsoever for any results or any use made of the results obtained from these programs, nor for any damages or litigation that result from the use of these programs for any purpose.

ABSTRACT

The Storm Water Management Model (SWMM) is a dynamic rainfall-runoff simulation model used for single event or long-term (continuous) simulation of runoff quantity and quality from primarily urban areas. The runoff component of SWMM operates on a collection of subcatchment areas that receive precipitation and generate runoff and pollutant loads. The routing portion of SWMM transports this runoff through a system of pipes, channels, storage/treatment devices, pumps, and regulators. SWMM tracks the quantity and quality of runoff generated within each subcatchment, and the flow rate, flow depth, and quality of water in each pipe and channel during a simulation period comprised of multiple time steps.

This manual documents the OpenSWMM computational engine: the objects a model is built from, the format of the input file it reads, the files it reads and writes, the reports it produces, the programmatic C and Python interfaces, and the error and warning messages it emits. Detailed descriptions of the theory and numerical methods are in the separate reference manuals; the graphical application is documented separately (see below).

FOREWORD

OpenSWMM is the next generation of the EPA Storm Water Management Model, maintained and advanced as a community-driven open source project. It builds on the foundational work of EPA's SWMM, which was first released in 1971 and has undergone several major upgrades since then. OpenSWMM preserves the rich legacy of SWMM while advancing the codebase with modern architecture, improved modularity, enhanced performance, and support for model coupling through the HydroCouple framework.

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.

Urban wet weather flows

Urban wet weather flows

ACKNOWLEDGEMENTS

OpenSWMM builds on the original EPA Storm Water Management Model (SWMM), developed by the U.S. Environmental Protection Agency, Office of Research and Development. The original user's manual and SWMM 5 software were created by Lewis A. Rossman, Environmental Scientist Emeritus at the U.S. EPA. His extraordinary contribution to the field of stormwater modeling is gratefully acknowledged.

The original SWMM documentation was reviewed by Michelle Simon, Katherine Ratliff, and Anne Mikelonis, all of the U.S. EPA, by Robert Dickinson (Innovyze), Mitch Heineman (CDM Smith), Mike Gregory (CHI), and Nandana Perera (CHI).

See Authors & Contributors for the complete list of authors and contributors.

USING THE GRAPHICAL APPLICATION

This manual does not describe a user interface. The OpenSWMM graphical application, SWMMVis, has its own manual covering the map canvas, layers and coordinate reference systems, every editor and dialog, running simulations, plots and result animation, 2D meshing, and a set of tutorials:

https://www.hydrocouple.org/openswmm.gui/

Two tables that used to live in this manual now live there, because they are values typed into an editor rather than engine behaviour: the parameter tables (units, soil characteristics, curve numbers, Manning's n, culvert codes and standard pipe sizes) are A7 — Reference Tables, and the per-object property dictionaries are A9 — Object Property Index. The numbered messages this engine emits are also catalogued there, alongside the API codes the application shows next to them, as A8 — Error and Warning Codes.

Manual Contents

CHAPTER 1 - The Conceptual Model — CHAPTER 1 - The Conceptual Model
CHAPTER 2 - Input File Reference — CHAPTER 2 - Input File Reference
CHAPTER 3 - Files and Command-Line Operation — CHAPTER 3 - Files and Command-Line Operation
CHAPTER 4 - Status Report; Summary Tables and Output — CHAPTER 4 - Status Report; Summary Tables and Output
CHAPTER 5 - Programmatic C API; Python Bindings and Plugins — CHAPTER 5 - Programmatic C API; Python Bindings and Plugins
CHAPTER 6 — Storage-node LIDs: Implementation and Interfaces — CHAPTER 6 - Storage-node LIDs: Implementation and Interfaces
CHAPTER 7 — Two-Dimensional CPU Implementation and Qualification — Chapter 7: Two-Dimensional CPU Implementation and Qualification
APPENDIX A - Error and Warning Messages — APPENDIX A - Error and Warning Messages

WHERE THE OLD CHAPTERS WENT

This manual replaces the former OpenSWMM User Manual, which mixed engine reference material with instructions for the retired Delphi user interface. The interface chapters are superseded by the SWMMVis manual linked above; the engine chapters were kept and renumbered. Anyone holding a citation to the old numbering can find its destination here.

Former chapter	Now
Ch. 1 – Introduction	this page
Ch. 2 – Quick Start Tutorial	T1 — Site Drainage with Water Quality
Ch. 3 – SWMM's Conceptual Model	CHAPTER 1 - The Conceptual Model
Ch. 4 – SWMM's Main Window	02 — The Interface
Ch. 5 – Working with Projects	03 — Working with Projects
Ch. 6 – Working with Objects	12 — Editing the Network on the Map
Ch. 7 – Working with the Map	05 — The Map Canvas and 07 — Layers and Data Sources
Ch. 8 – Running a Simulation	20 — Running a Simulation and 18 — Simulation Options
Ch. 9 – Viewing Results	CHAPTER 4 - Status Report; Summary Tables and Output (report content); 21 — Results Layers, Result Styling and Animation and 24 — Tabular Results and Reports
Ch. 10 – Printing and Copying	05 — The Map Canvas
Ch. 11 – Files Used by SWMM	CHAPTER 3 - Files and Command-Line Operation
Ch. 12 – Using Add-In Tools	retired; superseded by the plugin system
Ch. 13 – Programmatic C API	CHAPTER 5 - Programmatic C API; Python Bindings and Plugins
App. A – Useful Tables	A7 — Reference Tables
App. B – Visual Object Properties	A9 — Object Property Index
App. C – Specialized Property Editors	13 — Hydrology: Rain Gages, Subcatchments, LID, Snow, Groundwater and RDII; 14 — Hydraulics: Nodes, Links, Cross-Sections, Streets, Inlets and Controls; 16 — Water Quality, Reaction Systems, Water Age and Heat
App. D – Command Line SWMM	CHAPTER 2 - Input File Reference (format) and CHAPTER 3 - Files and Command-Line Operation (command line)
App. E – Error and Warning Messages	APPENDIX A - Error and Warning Messages

Table of Contents