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USGS StreamStats is a free, GIS-based web application from the U.S. Geological Survey. A researcher or engineer selects a point on a stream, the application delineates the drainage area above it, reports basin characteristics, and (where the state or region supports it) estimates flow statistics for that point. This guide walks through that workflow, the real interface terms, and the checks that make the output usable in a methods section. Facts below come from the USGS StreamStats pages read on 2026-11-07.
What StreamStats is
StreamStats is a web application for water-resources planning and management and for engineering design. It does three things: it delineates drainage areas for user-selected points on streams, it computes basin characteristics for the delineated area, and it provides estimated streamflow statistics. It also displays USGS data-collection stations (streamgages, shown as triangles) together with their flow statistics. For the surrounding field, see what hydrology covers as a research area.
Who runs it and what it covers
The application is run by the U.S. Geological Survey. Coverage is not uniform: it varies by state, and some states are not implemented because the local Water Science Center could not secure cooperative funding. Check which states or regions are available before planning a study area outside your home state.
USGS reports that StreamStats ran 605,106 delineations between 16 March 2024 and 15 March 2025, with a median delineated basin of 2 square miles, and that use clusters near cities and transportation corridors. The tool is therefore routinely used for small, local basins.
How a delineation and flow estimate works
Data behind the boundary
Delineations are derived from elevation data. USGS processes 3DEP elevation data to match the high-resolution National Hydrography Dataset (NHD) streams and Watershed Boundary Dataset (WBD) boundaries, and states that these NHD/WBD-conditioned delineations are generally superior to those produced from 3DEP alone. Other datasets supply water features, historic climate, soils and land use.
Basin characteristics
Basin characteristics are numeric descriptors of the delineated area. Examples listed by USGS are drainage area, stream slope and mean annual precipitation. Which characteristics are available varies by state and by site.
Flow statistics at ungaged sites
For a site with no streamgage, StreamStats estimates flow statistics with regional regression equations that relate statistics computed at streamgages to basin characteristics. Examples of statistics are the 1-percent flood, mean flow and the 7-day 10-year low flow. The equations are usually developed state by state through cost-sharing arrangements, so the equation set (and its published report) differs from state to state. Ungaged estimates assume natural flow unless the State/Regional Info page for that area says otherwise. USGS also maintains the National Streamflow Statistics (NSS) application, which holds USGS flood-frequency equations nationwide.
How to delineate a watershed and get statistics
The USGS How-To guides are organised around the interface sections named below, and the steps use those terms. Consult the matching guide for exact button behaviour in the current version.
- Open the application from the StreamStats page (streamstats.usgs.gov/ss/). It runs in current desktop and mobile browsers (recent Edge, Chrome or Firefox).
- Use the sidebar Select a State/Region step to choose the area. Read the State/Region Specific information, since equations and available characteristics depend on it.
- In Identify a Study Area, zoom to level 15 or greater so the gridded stream network appears, then select the site on a stream.
- Inspect the boundary the application returns. Use Editing a Basin to correct it, or clear it and try another point; the boundary can also be downloaded.
- Compute basin characteristics, then use Select Scenarios to choose the flow-statistic scenario that applies.
- Use Build a Report to produce the output. USGS documents a guide titled Reports for User-Selected Ungaged Sites.
- To look at gaged locations, zoom to level 9 or higher: streamgage triangles appear, and clicking or tapping one gives its information (see Getting Information for Streamgages).
Strengths and limits
| Strength | Limit |
|---|---|
| One interface returns a boundary, basin characteristics and flow estimates for a chosen point. | Coverage depends on state cost-sharing; some states are not implemented. |
| NHD/WBD-conditioned delineations are generally superior to those from 3DEP directly. | Elevation-based delineations can contain errors, especially in flat areas; USGS says to check delineations carefully. |
| Streamgage locations and their statistics are visible on the same map. | Ungaged estimates assume natural flow unless the State/Regional Info page states otherwise. |
| Regional regression equations are published per state. | The ratio-based method from version 2 is not available in version 4. |
The USGS pages give no quantitative accuracy figure for delineations, so do not attach one to your results; describe the checks you performed instead.
A reproducibility and citation checklist
USGS does not publish citation guidance on the StreamStats pages, so the following is an editorial recommendation for your methods section, not a USGS requirement.
- Record the state or region selected, the application version (a recent release listed by USGS is v4.30.0, 12 December 2025) and the date accessed.
- Save the delineated boundary and the basin characteristic values, and note whether you edited the basin.
- Cite the state report behind the regression equations you relied on, and keep the report generated by Build a Report.
- Deposit boundaries and outputs with descriptive metadata, and plan them in your data management plan. See versioning research datasets for tracking changes, and USGS ScienceBase as one USGS repository.
Related USGS tools
USGS lists these tools alongside StreamStats. Descriptions are limited to what the listing states.
| Tool | Listed by USGS as |
|---|---|
| National Streamflow Statistics (NSS) | Holds USGS flood-frequency equations nationwide |
| Batch Processing Tool | A StreamStats batch option (streamstats.usgs.gov/ss/?BP=submitBatch) |
| PeakFQ | Flood-frequency software; a USGS user notice says computational and sequencing issues with Bulletin 17C guidelines may produce erroneous estimates in some cases |
| Raindrop Trace, Upstream Network Trace, Time of Travel Beta, National StreamStats Beta, PROSPER, Regulation | Other tools named on the StreamStats page |
FAQ
Is there a StreamStats API or documentation?
Yes. USGS publishes how-to guides at usgs.gov/streamstats/how-guides and a services documentation site linked from the application (streamstats.usgs.gov/docs/streamstatsservices/). Read the services documentation directly for service details.
Can I process many sites at once?
USGS lists a Batch Processing Tool for StreamStats. Check the State/Region information for whether your area is supported.
Why does a delineation look wrong?
Delineations come from elevation data and can contain errors, especially in flat areas. Zoom in, check the boundary against the stream network, and use the basin-editing tool.
Is every U.S. state covered?
No. Coverage varies, and some states are not implemented.
Where are the help and report links?
The Help, About, and Report Links how-to guide describes them. Questions can go to [email protected].
Sources
- USGS, StreamStats, read 2026-11-07.
- USGS, StreamStats Fundamentals, read 2026-11-07.
- USGS, StreamStats How-To Guides, read 2026-11-07.
- USGS, StreamStats Delineations: Where Are They?, read 2026-11-07.
- USGS, PeakFQ software user notice, read 2026-11-07.
