Drought affecting how Corps officials manage Chittenden Locks

Published June 19, 2015

SEATTLE – U.S. Army Corps of Engineers officials anticipate Lake Washington’s level will drop below 20 feet this summer, the first time since October 1987, and are taking steps to conserve water during this year’s drought.

Current forecasts indicate the lake could drop below 20 feet by August with levels continuing to drop until September or October. A lake level drop to 19 feet or lower is possible given the extremely low inflows to the lake this year and recreation vessels should expect delays at the Hiram M. Chittenden Locks, or Ballard Locks as they are locally known.

The Corps typically maintains the water level between 20 and 22 feet, officially measured at the Chittenden Locks. Corps officials keep winter levels at 20 feet, and begin the annual summer refill in February, targeting a 22-foot refill by late May to early June. The higher level helps meet summer water use, providing water necessary for fish passage, navigation and salinity control.

Early concerns prompted Corps water managers to speed up the annual refill. The lake reached a 21.95 foot elevation in early May this year. However, record low inflows mean the lake level is dropping faster than normal, already nearing mid-summer levels, at just above 21 feet.

The Corps is now maximizing lockage efficiency by increasing the number of recreational vessels in each locking and adding more recreational vessels with commercial vessels. By increasing the number of vessels for each locking, recreational vessels could experience up to one hour delays waiting for additional vessels to arrive. As lake levels change, additional measures could be implemented.

The Corps also began conserving water in April by limiting water used to operate the juvenile salmon, or smolt, flumes.  Four flumes are installed each spring to help provide juvenile salmon and steelhead safe passage into Puget Sound. Due to the low water conditions only two flumes were initially operated. This has since been reduced to one.

Corps officials are recommending floating home owners, others with floating structures and vessels moored on Lakes Washington and Union and along the Ship Canal prepare for lower water levels. A recommended preparation level is 18.5 to 19 feet. The record low lake level is 18.35 feet, reached in 1958.

“Water management is about balance,” said Seattle District Senior Water Manager Ken Brettmann, who oversees reservoir regulation at the Corps’ Western Washington projects. “At the Locks, for example, in most years we can manage releasing 2 feet of stored water throughout the summer and meet all projects needs. This year will be extremely challenging and we’re balancing water conservation across lines to minimize impact to commerce, fish and the public.”

Several months of historic low streamflow throughout much of Washington is due to record low snowpack and extremely dry conditions since April.  Gov. Jay Inslee declared a state-wide drought for Washington in May.

For more information about Locks activities visit http://bit.ly/BallardLocks or follow on Facebook, www.facebook.com/ChittendenLocks, or Twitter, www.twitter.com/ChittendenLocks.
Bill Dowell

Release no. 15-021