Storage from official US gauges (USGS, USACE, Bureau of Reclamation, CDEC). Fill % uses design capacity from the National Inventory of Dams where available; a few sites without a match fall back to the 5-year maximum.

About reservoirs in Idaho

As of September 10, 2026, the reservoirs we track across Idaho that report live levels hold roughly 1,812 hm³ of water — about 25.4% of their combined capacity. Taken together, Idaho's reservoirs are low.

Across the region, 3 reservoirs are at critically low levels and 9 are low. Black Canyon Reservoir is the fullest at 96.4%, while Mann Creek Reservoir is the lowest at 1.7%.

Over the most recent week on record, 1 reservoir rose and 8 reservoirs fell across Idaho.

Storage figures for Idaho come from USGS · USACE · BOR · CDEC; the most recent reading is from September 10, 2026. Each reservoir below links to its own page with full history and seasonal context.

Idaho at a glance

Reservoirs tracked: 20
Average fill: 25.4%
Water stored: 1,812 hm³
Combined capacity: 7,144 hm³
At critically low levels: 3
Fullest: Black Canyon Reservoir (96.4%)
Lowest: Mann Creek Reservoir (1.7%)
Last updated: September 10, 2026

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