An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Environmental Modeling Community of Practice

BASINS Technical Notes

EPA has developed several technical notes that provide in depth information on a specific function in BASINS. Technical notes can be used to answer questions users may have, or to provide additional information on the application of features in BASINS.

Note: References in the technical notes are made to NPSM (NonPoint Source Model) which was the predecessor to WinHSPF (Windows Hydrological Simulation Program - Fortran) in BASINS 3.0. Please substitute "WinHSPF" for "NPSM" in the Technical Notes.

You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.