The Hiram M. Chittenden Locks recently experienced its highest water inflow event since detailed record-keeping began in 1946 according to William Dowell, public affairs officer for the Seattle District of the Army Corps of Engineers. The Locks spillway (shown with all six spillways open, an unusual occurrence) had big water flow events in February 1996 and January 2009, but the three-day inflow volume Feb. 7-9 appears to be larger than anything else in the database, according to Dowell.
The peak one-day inflow was between 15,000 and 16,000 cubic feet per second (cfs). Peak one-day outflow was 13,500 cfs.
The Ballard Locks are different from most dams in that there are no downstream concerns. Howard Hanson Dam on the Green River and Mud Mountain Dam on the White River are flood-risk-reduction dams — they hold back water to reduce flood risk downstream. “At the Locks there are no downstream risks, and we were releasing as much water as possible through the spillway,” said Dowell.