Lower Snake River water temperature during the summer is too hot for salmon migration. For the last 20 years, over 64 percent of the time during the summer, water temperature is too hot and exceeds 68 degrees. Higher water temperatures during migration increases prespawning mortality and deplete energy reserves before fish reach spawning grounds, reducing the size and number of viable eggs. The Snake River does not have enough adult salmon returning to prevent extinction and hot water kills adult salmon migrating up the Snake River. The Snake River has the hottest temperature during the upstream migration of adult chinook and sockeye salmon.
The Snake River is hotter than the Columbia River upstream of the Snake River confluence. For the last 10 years, the Columbia River exceeds 68 degrees about 20 percent of the time each summer while the Snake River exceeds that temperature over 72 percent of the time.
While U.S. Sen. Patty Murray and Gov. Jay Inslee pursue a joint federal-state process to establish a comprehensive solution for salmon recovery in the Columbia River Basin, please include reducing water temperature in the Snake River during salmon migration. The solution could modify the Lower Snake River dams to reduce water temperature during adult migration. The other option is to implement Congressman Mike Simpson’s Columbia Basin Initiative to restore Idaho’s salmon and steelhead to abundance while ensuring Idaho and Northwest communities a prosperous future. Last, I urge everyone to work to reduce Lower Snake River water temperature during salmon migration.