Army Corps begins annual spring fill of Howard Hanson Dam

Published March 15, 2016

Seattle – Water managers have begun slowly filling the reservoir at Howard Hanson Dam at the headwaters of the Green River. As is typical, the Army Corps of Engineers slowly begins annual spring fill of the reservoir in late February, allowing water levels to rise within Howard Hanson Dam’s reservoir. 

The process takes roughly three months to refill the reservoir. The current plan targets a maximum pool elevation of 1,167 feet above sea level. A 1,167 foot elevation pool has been the spring refill target since 2007. 

Water stored during the spring refill of the reservoir will be used to augment downstream flows to help endangered species of fish, including Chinook and steelhead. Project managers believe that the regulated downstream flows will aid spawning and other life-cycle events for the fish. Additionally, some of the stored water will be used to provide water supply to the City of Tacoma and its water supply partners.

Snowpack in the Green River Basin is near average conditions and the water supply outlook for the spring is for average to above average runoff based on the current snowpack and wet basin soils following well above average precipitation over the last few months. This year’s favorable water supply outlook is in sharp contrast to last year, which experienced record low spring runoff in the basin and presented challenging refill conditions.

The Corps operates the Howard Hanson Dam project, which provides flood risk management to the Green River valley, low-flow augmentation to the Green River for environmental benefits, and water supply to the City of Tacoma and its water supply partners.

For more information call Tanya King, U.S. Army Corps of Engineers, Seattle District, public affairs at 206-764-3750 or email at

Current reservoir information is available on line at:

Public Affairs Office

Release no. 16-009