Army Corps to raise Lake Washington to Summer elevation this month

For the second consecutive year, U.S. Army Corps of Engineers officials will raise lakes Washington and Union earlier than typical to the target summer 22-foot elevation due to lower than normal inflows.

After a good start, the lake is currently at elevation 21.8 feet, typical for early May and consistent with normal annual operations. However, because of recent dry conditions and forecasts, and significantly earlier than normal snowmelt, Corps water managers intend to complete refill by mid-May instead of the usual June 1 target date.

“If we wait until late May, there may not be sufficient lake inflow to get us to elevation 22 feet,” says Ken Brettmann, senior water manager with the Seattle District, U.S. Army Corps of Engineers.

Getting the lake to 22 feet is extremely important since every inch of water in the 2-foot operating band is needed for fish passage, lockages, and managing water quality throughout the season.

Refilling early last year helped immensely during the record-breaking drought but Corps officials still needed to alter lock operations.

Even with the operational changes of the early refill, limiting water usage for smolt flumes, maximizing lockage efficiency and delaying lockages, the lake briefly fell below the 20 foot minimum elevation water managers try to maintain.

“Last year’s challenging drought conditions reinforced how important it is to fill the lake to the 22 foot elevation each year,” said Brettmann.

Depending on conditions, the lake may remain at full pool through June.

The official lake level is measured at the Locks. Lake Washington levels may vary due to the natural gradient between the lake and the locks or wind that can push the lake levels up for short periods of time.

Vessel owners should closely monitor lake elevations and adjust mooring lines as necessary.

More information on Lake Washington’s status is available on the Corps’ Seattle District Reservoir Control Center website.