Modernized access for USGS rating curves is now available
A new STAC API provides access to rating curve files. This API will replace the ratings depot in winter 2026.
Modernized access for USGS rating curves is now available
The USGS publishes rating curves describing the relationship between stage and streamflow at a monitoring location. Historically, these curves have been published at the NWISWeb Ratings Depot, available at https://waterdata.usgs.gov/nwisweb/get_ratings .
Rating curve files are now available from the USGS Water Data STAC API, available at https://api.waterdata.usgs.gov/stac/v0/ . The STAC (short for “SpatioTemporal Asset Catalogs ”) API allows users to search across USGS data collections using a standardized metadata format and provides access to data in its native formats, providing a modern, standardized interface for discovering and accessing available data. Documentation for how to use this API to access rating curve files is available at https://api.waterdata.usgs.gov/docs/stac .
The STAC API provides access to rating curves in identical formats to the Ratings Depot; there is no change being made to how to read or interpret these files. The URLs to access these files will change, however. For example, the file located at https://waterdata.usgs.gov/nwisweb/data/ratings/exsa/USGS.06652000.exsa.rdb will now be downloaded from https://api.waterdata.usgs.gov/stac-files/ratings/USGS.06652000.exsa.rdb .
The Ratings Depot is scheduled to be decommissioned during winter 2026 as part of NWISWeb Decommission Campaign 3 . After this time, the STAC API will be the only way to access rating curve files. Users are recommended to migrate to the STAC API before this time.
We have staff ready to help you make the transition should you need it. Please reach out to us at wdfn@usgs.gov with any questions.
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Background
For over 15 years, the USGS has provided machine-readable and automated access to water data via the WaterServices family of application programming interfaces (APIs), which are hosted at https://waterservices.usgs.gov/ . These APIs underpin all other USGS web delivery products – including products such as the National Water Dashboard and Water Data for the Nation (WDFN) – and have been incredibly effective at delivering water data to the public. Between October 2024 and March 2025 alone, these legacy APIs have handled more than 1.6 billion requests from almost 3.5 million distinct IP addresses.