River streamflow (USGS gages)
Annual mean discharge at twelve long-record USGS stream gages on Idaho's major rivers, computed by USGS from approved daily discharge readings.
Figures
Cubic feet per second
Source: U.S. Geological Survey, USGS Surface-Water Annual Statistics, Idaho streamgages. Data period 2025.
Pages built on this dataset
Publisher
- Organization
- U.S. Geological Survey
- Publisher’s dataset
- USGS Surface-Water Annual Statistics, Idaho streamgages
- File or API used
- https://waterservices.usgs.gov/nwis/stat/
- Methodology
- https://help.waterdata.usgs.gov/faq/about-statistics
Coverage
- Geography
- Twelve USGS stream gages on the Snake, Boise, Salmon, Clearwater, Kootenai and Bear rivers in Idaho
- Time coverage
- 1910-2025 (varies by gage)
- Update frequency
- Annual
- Retrieved
- September 16, 2026
- License of the records
- Public domain. U.S. federal government work.
- Rows
- 1,096 observations, 1910-2025
Measures
| Measure | What it measures | Unit |
|---|---|---|
| Mean streamflow | Mean discharge over the calendar year at a USGS stream gage. | cfs |
Caveats
- Each figure is the mean of daily mean discharge over a calendar year, in cubic feet per second, as computed by USGS's own annual statistics service from approved (not provisional) daily readings.
- USGS's own convention for an annual streamflow figure is the water year, 1 October to 30 September; this dataset stores calendar years instead so the series lines up with every other year on this site.
- At Milner and at Porthill the figure is USGS's "total flow" statistic, which adds diverted or bypassed water back to the channel reading, so those two are not directly comparable to a plain gage reading elsewhere on the same river.
- Shoshone Falls sits on the Snake River between the Kimberly and Twin Falls gages; the Kimberly gage is the closest gage upstream of the falls and the Twin Falls gage the closest downstream. Milner Dam, upstream of both, diverts most or all of the river's flow for irrigation in the growing season, so neither gage's reading is a measurement of flow over the falls.
How to cite
Understand Idaho, “USGS Surface-Water Annual Statistics, Idaho streamgages”, compiled from U.S. Geological Survey, USGS Surface-Water Annual Statistics, Idaho streamgages. Retrieved September 16, 2026. https://understandidaho.com/data/usgs-streamflow/.
Cite U.S. Geological Survey directly for the figures themselves.
This page was last updated .