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.

Major reservoirs — data pending

⏳

Lake Frances Reservoir — data sourcing in progress

Storage is monitored by the US Bureau of Reclamation (BOR RISE), but the live feed is currently stale — we are working to restore it. Known capacities: Lake Frances Reservoir (0.1 km³).

Lake Frances Reservoir

Sourcing

Capacity: 136 hm³⏳ Pending

About reservoirs in Montana

As of September 10, 2026, the reservoirs we track across Montana that report live levels hold roughly 27,956 hm³ of water — about 81.0% of their combined capacity. Taken together, Montana's reservoirs are high.

Across the region, 2 reservoirs are at critically low levels and 8 are low. Helena Valley Reservoir is the fullest at 97.1%, while Gibson Reservoir is the lowest at 7.7%.

Over the most recent week on record, 8 reservoirs rose and 5 reservoirs fell across Montana.

Storage figures for Montana 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.

Montana at a glance

Reservoirs tracked: 24
Average fill: 81.0%
Water stored: 27,956 hm³
Combined capacity: 34,535 hm³
At critically low levels: 2
Fullest: Helena Valley Reservoir (97.1%)
Lowest: Gibson Reservoir (7.7%)
Last updated: September 10, 2026

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