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Who this is for: researchers, engineers and students who need USGS streamflow, groundwater or water-quality data and want to know what the data types are, how to retrieve them, and what changes when the legacy WaterServices interface is retired. Data below were checked against the USGS service pages on 2026-11-08.
Short answer
NWIS data are the U.S. Geological Survey’s water measurements from streams, lakes and wells. The legacy WaterServices interface that scripts used to retrieve them is scheduled for permanent shutdown on February 22, 2027, and users must migrate to the USGS Water Data APIs.
Definition and scope
The National Water Information System (NWIS) is the name long used for the U.S. Geological Survey’s water data holdings: measurements of streams, lakes and wells collected at USGS monitoring locations. Programmatic access to those data has been offered through the USGS WaterServices REST interface, which is being replaced by the USGS Water Data APIs. For anyone who writes scripts against NWIS data, the interface change is the practical issue.
How the data are used in practice
Researchers retrieve NWIS data programmatically or through portals. The main data types are:
- Instantaneous (real-time) values: near real-time data from thousands of sites. USGS states that readings are usually made every 15 minutes and transmitted hourly.
- Daily values: daily summaries such as mean, median, maximum and minimum, with a decade or more of record at many sites.
- Site information: descriptive records for millions of sites, of which thousands report in real time.
- Statistics: daily, monthly and annual statistics computed on approved data from time-series sites.
- Groundwater levels: historical, manually recorded water levels.
- Discrete water quality: reachable through the Water Quality Portal, which combines data from USGS, EPA and other state, federal, tribal and local agencies, and through the USGS Samples API.
Types or related concepts: legacy WaterServices versus the new Water Data APIs
The WaterServices home page carries a notice that the service will be permanently shut down on February 22, 2027, that requests will be intentionally slowed and outages introduced beginning in January 2027, and that users must migrate to the new APIs. The table maps each legacy service to the modern endpoint that serves the same kind of data, using only pairings that the two USGS pages describe.
| Legacy WaterServices | Water Data API endpoint | What it returns |
|---|---|---|
| Instantaneous Values | Continuous Values | Most recent real-time measurements, such as streamflow and gage height, for USGS monitoring locations |
| Daily Values | Daily Values | Historical daily summaries (mean, median, maximum, minimum or other derived values) for streams, lakes and wells |
| Site service | Monitoring Locations | Name, identifier, responsible agency, date established, location type (stream, lake, groundwater), state, county, latitude and longitude, and hydrologic unit code (HUC) |
| Statistics | Statistics | Summary statistics for time-series sites |
The new APIs also list a Time Series Metadata endpoint, which describes each time series (one parameter at one monitoring location), including units of measurement and the dates of the earliest and most recent observations, and OGC-compliant API collections. USGS offers an API key through the new API site.
Where it matters for research workflows
- Scripts and workflows: any code, notebook or pipeline that calls waterservices.usgs.gov needs to be pointed at api.waterdata.usgs.gov before the January 2027 slowdowns begin.
- Reproducibility: record which interface and retrieval date produced a dataset, since the legacy interface will stop answering. Our guides on USGS StreamStats and NOAA Atlas 14 cover related federal hydrology tools.
- Water quality: sample-based chemistry is served through the Water Quality Portal and the USGS Samples API rather than the time-series endpoints.
For background on the field these data support, see what is hydrology; for other public environmental data sources see EPA Envirofacts and the ECOTOX database.
Common misunderstandings
- NWIS is not a single download. It is a body of data reached through several services; sample-based water chemistry is served separately from time-series values.
- Retirement of WaterServices is not retirement of the data. USGS directs users to the Water Data APIs, which serve the same kinds of data.
FAQ
What is the USGS National Water Information System?
It is the USGS’s collection of water data from monitoring locations on streams, lakes and groundwater, accessed through USGS web services and portals.
Is the USGS WaterServices API going away?
Yes. USGS states it will be permanently shut down on February 22, 2027, with intentional slowdowns and outages from January 2027.
Where do I get the replacement?
At api.waterdata.usgs.gov, which offers Continuous Values, Daily Values, Monitoring Locations, Time Series Metadata, Statistics, Samples and OGC-compliant APIs.
How often is real-time data updated?
USGS states that readings are usually made every 15 minutes and transmitted hourly.
Sources
- U.S. Geological Survey, WaterServices and WaterServices documentation, read 2026-11-08.
- U.S. Geological Survey, USGS Water Data APIs, read 2026-11-08.
