News Releases

Corps begins flexible spring spill operations to benefit fish and hydropower

Northwestern Division
Published May 8, 2020
The U.S. Army Corps of Engineers began implementing its 2020 Fish Operations Plan at the four lower Snake River dams April 3 and at the lower Columbia River dams April 10. The 2020 plan includes spill and transport operations for the spring and summer juvenile fish passage seasons at these dams, as specified in the NOAA Fisheries 2019 Columbia River System Biological Opinion and the 2019-2021 Spill Operation Agreement.

Spring spill in 2020 reflects the implementation of 24-hour flexible spill operations for the purpose of supporting downstream juvenile fish passage while also providing operational flexibility that allows federal power system benefits at these dams. In 2020, spill levels will increase up to the new state water quality standards of 125% total dissolved gas (TDG) at many dams. This is an increase in spill from the 120% TDG spill levels implemented in 2019.

“This year’s operation allows us to continue to take advantage of the off-peak, lower power demand hours to provide 16 hours of spill for juvenile fish passage, while reducing spill for up to eight hours during periods of greater power demand,” said Tim Dykstra, senior fish program manager for the Corps’ Northwestern Division.

This operation is based on the 2019 collaborative agreement that the Corps, the Bonneville Power Administration, the Bureau of Reclamation, the states of Oregon and Washington, and the Nez Perce Tribe reached to implement this flexible spring spill operation. Continuing flexible operations help the region learn whether spill for juvenile fish passage, up to the maximum total dissolved gas level allowable by the states, further improves the survival of juvenile salmon and steelhead and, over time, improves adult returns, while also keeping in balance costs in hydropower generation.

Dykstra added that since this operation involves spilling much more water at these dams for juvenile fish passage than in previous years, the agencies will monitor the river system closely and adjust spill as necessary if they observe any unintended consequences from the higher spill.

The transition to summer spill begins on June 21 at lower Snake River dams and June 16 at lower Columbia River dams. Summer spill for juvenile fish passage ends at all eight dams at midnight on September 1, although late summer spill levels will be reduced from 2019 levels starting August 16 to offset the hydropower impacts from higher spill in the spring months.

The most recent water supply forecast for 2020 issued April 24 by the Northwest River Forecast Center for the Columbia River Basin (Apr–Aug) is 95 percent of normal as measured at The Dalles Dam and 81 percent of normal for the Snake River Basin, (Apr–Jul), as measured at Lower Granite Dam.

Spring snow melt will result in high water levels and high velocities below the dams. River users, especially anglers, are reminded to be mindful of conditions and to always wear a personal flotation device when on or near the river. Boaters should expect spill to create unusual currents, eddies and turbulent conditions, particularly immediately downstream of the dams and near navigation locks.

In addition to spill, the federal agencies will continue many other actions in the current biological opinion that benefit salmon and steelhead. For more information on federal salmon and steelhead recovery efforts in the region, NOAA Fisheries’ 2019 Columbia River System Biological Opinion and the flexible spill agreement, visit

Matt Rabe

Release no. 20-049