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

⏳

2 major reservoirs — data sourcing in progress

Storage is monitored by the US Geological Survey (USGS NWIS) / the US Bureau of Reclamation (BOR RISE), but the live feed is currently stale — we are working to restore it. Known capacities: Mayfield Reservoir (0.2 km³), Banks Lake (1.6 km³).

Mayfield Reservoir

Sourcing

Capacity: 165 hm³⏳ Pending

Banks Lake

Sourcing

Capacity: 1,573 hm³⏳ Pending

About reservoirs in Washington

As of September 10, 2026, the reservoirs we track across Washington that report live levels hold roughly 799 hm³ of water — about 29.5% of their combined capacity. Taken together, Washington's reservoirs are low.

Across the region, 5 reservoirs are at critically low levels and 4 are low. Lake Tapps is the fullest at 89.5%, while Mud Mountain Lake is the lowest at 0.0%.

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

Storage figures for Washington 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.

Washington at a glance

Reservoirs tracked: 15
Average fill: 29.5%
Water stored: 799 hm³
Combined capacity: 2,710 hm³
At critically low levels: 5
Fullest: Lake Tapps (89.5%)
Lowest: Mud Mountain Lake (0.0%)
Last updated: September 10, 2026

ShareX LinkedIn WhatsApp