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Dam “Spill” Expected to Boost Columbia River Salmon and Benefit Orcas


More spring Chinook may return as adult salmon in a few years thanks to a new agreement negotiated by federal agencies, states, and tribes to test an innovative dam operation plan. Some estimates indicate that the new operation may produce an additional 10,000–60,000 adult spring Chinook per year.

While adult salmon returns will also be influenced by ocean conditions and river flows, the new “flexible spill” agreement just going into effect promises to be a “win-win” for fish, hydropower production, and orca.

Hydropower is the largest source of clean, low carbon energy in the Northwest. The new agreement aims to preserve the value of this clean energy resource while improving the status of Columbia basin salmon.

Washington entered into the “Flexible Spill Agreement” in December. The agreement will be in effect for the next two or three years (depending federal progress toward a longer-term Columbia-Snake River Biological Opinion). It increases spill (the amount of water going over a dam as opposed to through dam turbines) during the times of day when regional energy demand is lower, and ramps down spill to allow for more hydropower generation when demand is higher.

Taking advantage of this daily swing in demand — which is created in large part by the recent deployment of new clean energy sources like solar and wind — involves spilling at higher levels with higher Total Dissolved Gas (TDG) caps for up to 16 hours/day and lower 2014 BiOp levels for eight hours a day, when there is higher energy demand. The new levels of spill are intended to allow for higher survival for juvenile fish as they move through the dams and enter the ocean while keeping TDG levels low enough not to harm salmon or other aquatic species — an area of a recent study. The dams will spill up to 120% TDG in 2019 and up to 125% in 2020.

Washington (including WDFW) helped negotiate this agreement, which was signed by Washington, Oregon, three federal agencies (Bonneville Power Administration, U.S. Army Corps of Engineers, and U.S. Bureau of Reclamation) and the Nez Perce Tribe. The agreement is also supported by Idaho, Montana, and the Columbia River Inter-Tribal Fish Commission.

The agreement should help salmon, protect Bonneville Power Administration revenues, and simplify river management for the Army Corps of Engineers. This strategy may set the stage for a longer-term dam operation strategy as well.

If they perform as expected, this change should provide meaningful near-term benefits for adult spring Chinook salmon numbers, and thereby increase food for southern resident killer whales.

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