Current Release: Version 1.3 (Updated October 2026) — see CHANGELOG.md for what changed.
The current release of the sewershed data is located in this folder (Current_Release.zip) and will always be maintained using the permanent link: https://github.com/USEPA/Sewersheds/blob/main/Current_Release.zip
As versions are replaced, they will be maintained in the folder 'Version_History'. Release notes for every version are in CHANGELOG.md; full notes and column descriptions for the current release are in Version_History/V_1_3/readme.md.
"The Clean Watershed Needs Survey(CWNS) provides an assessment of the capital investments necessary for states, the District of Columbia, and U.S. Territories to meet the Clean Water Act’s (CWA) water quality goals over the subsequent 20 years. These needs include projects and related infrastructure costs for wastewater publicly owned treatment works, stormwater treatment, nonpoint source control, and decentralized wastewater treatment. The U.S. Environmental Protection Agency (EPA) has prepared the 2022 CWNS Report to Congress in compliance with CWA section 516(b)(1)(B) (33 U.S Code §1375) as well as CWA section 609, which was added by the Infrastructure Investment and Jobs Act (IIJA), P.L. 117-58, November 15, 2021. This Report summarizes the results of EPA’s 17th survey since the CWA was enacted in 1972."
As part of this survey, state-level teams submit technical information about publicly owned treatment works (POTWs). Some POTWs may discharge a portion of their wastewater downstream to other POTWs. When a treatment plant discharges less than 50% of its wastewater to another POTW, we refer to it as an 'endpoint', meaning that it is considered the final destination for wastewater prior to treatment and then discharge back into the environment, most frequently via direct discharge into a water body such as a river or ocean. The entire sewered area that contributes wastewater to a specific endpoint is referred to as a 'sewershed'. A sewershed may therefore include a single POTW and collection system or multiple POTWs and their collection systems. The relationship between POTWs and endpoints can be derived from CWNS reporting by accounting for reported discharge of wastewater between facilities.
Sewershed extents are not a part of reporting within the CWNS and are otherwise not statutorily required under the CWA. Understanding the sewered area related to an endpoint is critical to support the CWA, as well as multiple other agency and administration priorities. Sewershed boundaries can, for example, facilitate wastewater surveillance efforts and link community disease tracking to affected populations. The ability to map sewer systems can also be critical to infrastructure and urban planning, providing information on areas that can be developed or could benefit from resources to aid in economic development and information on infrastructure gaps.
EPA previously developed geospatial data for community water system service areas for the United States. The development of sewershed boundaries was built off of this experience, using machine learning models which are trained on existing sewershed data and utilizing advanced geospatial techniques to account for the complexities of determining what areas of the United States are sewered and which treatment plants they are served by. The output of this dataset is a spatial dataset of polygons that are constructed from hexagons with a resolution of ~0.11 km^2^. In total, 17,012 sewersheds are present in the data (Version 1.3), with 3,279 obtained from a variety of public sources and 13,733 modeled using machine learning. Sourced sewersheds cover 46% of the sewered population. Sewersheds do not overlap.
For information related to this repository, please contact: Andrew Murray (Murray.AndrewR@epa.gov).
This repository reused material from GSA, 18F , Lawrence Livermore National Lab, and from the Consumer Financial Protection Bureau's policy.
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