SWMM Testing Protocol

Overview

Over the past decade the number of SWMM forks and derivative engines has grown quickly. Practitioners and reviewers need a reliable way to know whether a given engine produces results consistent with the reference implementation.

This task committee is assembling a standard, version-controlled set of test models that exercise the full range of SWMM hydrology and hydraulics. The suite will be tied to specific SWMM versions, built on the standard INP, OUT and RPT file formats, and published openly so that any developer can run it.

Focus areas

• Benchmark models covering every major SWMM process and routing method
• Acceptance criteria and tolerances for comparing engines
• Version control that ties each benchmark to a specific reference release
• A public GitHub repository of input files and expected results

Recent updates

1. February 2026

   Proposed at the February committee meeting. Members agreed the legacy test cases are too simple and outdated, and that the suite should be community-maintained. Because EPA cannot endorse third-party products, the suite is framed as a community benchmark rather than an EPA certification.

Milestones

• Proposal accepted by the committeeComplete
• Task committee formation and work planIn progress
• Collect benchmark models in a public repositoryPlanned
• Define acceptance criteria and publish version 1Planned