Idaho reservoir storage
Storage on 30 September each year and active (usable) storage capacity for the Bureau of Reclamation reservoirs on the Snake, Boise, Payette, Weiser, and Clearwater systems that serve Idaho irrigation, plus Jackson Lake and Grassy Lake in Wyoming, which are administered as upstream Snake River System storage for Idaho delivery.
Publisher
- Organization
- U.S. Bureau of Reclamation
- Publisher’s dataset
- Pacific Northwest Hydromet: Reservoir Storage and Active Capacity
- File or API used
- https://www.usbr.gov/pn-bin/daily.pl
- Retrieval script
scripts/fetch-usbr-reservoirs.py- Methodology
- https://www.usbr.gov/pn/hydromet/station.js
Coverage
- Geography
- Idaho (statewide; two of the twenty-one reservoirs, Jackson Lake and Grassy Lake, are physically sited in Wyoming)
- Time coverage
- 1910-2025 (storage, varies by station); 2013 (capacity)
- Update frequency
- Annual (storage, one value per water year); irregular (capacity, revised only after events such as a sedimentation survey)
- Published
- not stated
- Retrieved
- September 8, 2026
- License
- The compiled file on this page is CC BY 4.0. The underlying records: Public domain. U.S. federal government work.
Measures
| Measure | What it measures | Unit |
|---|---|---|
| Reservoir storage | Reservoir contents on 30 September each year, from Reclamation's Hydromet daily archive. | acre feet |
| Reservoir active capacity | Active (usable) storage capacity, from Reclamation Pacific Northwest Region's Monthly Reservoir Status Report. | acre feet |
Caveats
- Storage is read on 30 September each year, the approximate close of Idaho's irrigation season, so a low figure can reflect scheduled seasonal drawdown for delivery rather than drought; it is one dated reading per reservoir per year, not a live level.
- Reclamation labels this Hydromet data provisional and subject to revision.
- Active capacity figures come from Reclamation Pacific Northwest Region's Monthly Reservoir Status Report; the only edition served at that URL is dated May 2013, and Reclamation has not republished a newer one there. Active capacity changes only rarely (for example after a sedimentation survey), so the 2013 figure is still Reclamation's current published number for these reservoirs absent a newer edition.
- That report did not carry an active-capacity figure for four of the twenty-one reservoirs (Black Canyon, Henrys Lake, Payette Lake, and Lake Waha); water.reservoir_capacity has no observation for those four, while water.reservoir_storage covers all twenty-one.
- Jackson Lake and Grassy Lake are sited in Wyoming; they are included because Reclamation administers them as upstream Snake River System storage released for delivery to Idaho irrigators, the same reasoning the sibling lpag repo's reservoir puller already applied to Jackson Lake.
- Magic Reservoir, on the Big Wood River, is often grouped with these systems but is a State of Idaho project, not a Bureau of Reclamation one; it carries no code in Reclamation's Hydromet network and is not included here.
- Storage figures are stored to one decimal acre-foot as Reclamation's daily archive publishes them; capacity figures are converted from the report's thousand-acre-foot column to acre-feet.
- publisherUpdated is omitted: the storage series is updated after each 30 September while the capacity table was last republished in May 2013, so the two metrics in this dataset do not share one release date.
Pages built on this dataset
Downloads
How to cite
Understand Idaho, “Pacific Northwest Hydromet: Reservoir Storage and Active Capacity”, compiled from U.S. Bureau of Reclamation, Pacific Northwest Hydromet: Reservoir Storage and Active Capacity. Retrieved September 8, 2026. https://understandidaho.com/data/usbr-reservoirs/. CC BY 4.0.
Cite U.S. Bureau of Reclamation directly for the figures themselves.
This page was last updated .