Understanding the environmental impacts of more water over the dam

Spring spill season for dams along the Columbia and Snake rivers is approaching. During this time, generally from April through June, large amounts of runoff from the melting snowpack lead to high water flows. When hydropower operations cannot pass all of the water through turbines or store it, water is spilled over the dams through spill gates. Spill is used to manage incoming water and to help move juvenile salmon past dams, downstream towards the ocean. During this time, upwards of 100 million juvenile salmon migrate down the Columbia River.

Responding to the need for more salmon

Ecology, in support of the new agreement for flexible spill operations at four lower Columbia and four lower Snake River dams, is proposing a short-term modification that would allow more water to spill over the dams, with the goal of improving the survival of juvenile salmon migrating to the ocean. Under the flexible spill agreement, the increased spill would happen during hours of relatively low energy demand, balancing salmon survival rates while managing power costs.

Our proposal 

The goal of the short-term modification is to understand if allowing more spill will improve the survival of juvenile salmon migrating to the ocean without too great of impact on salmon, resident fish, invertebrates and other aquatic life in the rivers.

At this time, we are considering a short-term modification that would remove the 115% forebay criterion for up to three years. This action would coincide with the flexible spill agreement that aims to benefit salmon and hydropower. 

Learn about our Environmental Impact Statement

In order to do a short-term modification to our Water Quality Standards, we must complete an Environmental Impact Statement. Drafts of our Environmental Impact Statement and short-term modification are now available for public comment. The Environmental Impact Statement, while technical in nature, provides extensive information on current available science, research, and data related to total dissolved gas. It also contains a discussion of potential alternatives for developing a short-term modification. 

Save the date for our upcoming hearings 

We are planning two public hearings that will begin with a short presentation, followed by questions and answers. The hearing portion will begin shortly after the questions and answers are finished. During the hearing, you may give oral testimony and written comments. Written comments will receive the same consideration as oral testimony.