Breaching Lower Snake dams could help water temps, say scientists

Ice Harbor Dam/U.S. Army Corps of Engineers photo by David Lewis

We’ve talked a lot about the impact four dams on the Lower Snake River have on dwindling populations of salmon and steelhead as they migrate hundreds of miles to and from their natal streams in Idaho.

 

But last week scientists highlighted one more data point in the argument to further prioritize breaching the four dams: warming water temperatures.

 

More than 50 scientists delivered a letter to Northwest policy makers, reports Eric Barker of the Lewiston Tribune, asserting that only the removal of these four controversial dams could return water temperatures to a safe level in the summertime for salmon and steelhead.

 

The dams create slack water which sits in the sun during warm months. The EPA estimates that Ice Harbor, Lower Monumental, Little Goose and Lower Granite dams on the Snake River can cause a rise of 12 degrees when compared to the temperature of a free flowing river.

 

“Hot water kills cold-water fish. That is what is happening now, when adult salmon try to return home through reservoirs that are too warm for long periods of time.”

 

Dave Cannamela, retired Idaho Fish and Game fisheries biologist, quoted in the Lewiston Tribune.

 

And as climates change water temperatures remain high for longer periods of time, causing higher mortality rates.

 

As Idaho Governor Brad Little’s Salmon Workgroup meet this week to continue conversations on how to restore salmon and steelhead to Idaho, we hope the science throws some light on the conversation.

 

If you want to throw your two cents in, send your comments to species@osc.idaho.gov.