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Hot weather creates higher water temperatures, which can present significant problems – even death – for migrating adult salmon and steelhead. Studies have shown water heated to 68 degrees or more is problematic for fish. In these warm conditions, migrating fish slow down to save energy, becoming more susceptible to predators and infections. Slowing down can also delay their migration, preventing them from returning to spawn. Even worse, extreme heat above 70 degrees can result in death, killing fish by the thousands. 

Extreme heat significantly affects sockeye salmon because they migrate during June and July, facing the warmest river conditions. In 2015, a similar heat wave and drought combination devastated sockeye, killing 99% of returning Snake River sockeye before they reached Idaho. These are the fish that give Redfish Lake its name, and they are the most vulnerable of Idaho’s salmon species, in large part because of that mass die-off. 

A key difference between this heat wave and 2015 is how early these high temperatures are occurring.  Here are a few potentially devastating effects of heat and drought:  

  • High temperatures may affect Spring and Summer Chinook still migrating through the river system. These fish escaped the 2015 heat safely in their high-elevation spawning streams, but many are still in mainstem rivers now so may have been impacted by the heat this year. 
  • Fall Chinook may also be impacted. To cool water in the lower Snake River, federal dam operators release cold water from Dworshak Reservoir, just above Lewiston. These releases usually start after July 4, but this year began about 10 days earlier. The reservoir may not have enough water to sustain the releases through the end of summer, when Fall Chinook begin their migration. These Chinook may face an even hotter river, with no potential for cooler water from Dworshak. 
  • This summer could get even worse. July and August are typically warmer than June, and additional heat waves could be even worse for Idaho’s fish. 

A recent report shows dams are the greatest contributor to heat pollution in the Columbia-Snake River system. By slowing the flow and increasing the water’s surface area, four dams on the lower Snake River increase water temperature by as much as 5.7 degrees.

Drought also means less water to produce power at the dams. With rivers running low in May this year, the Bonneville Power Administration’s hydroelectric production was 31% lower than the same month last year. In a worst-case scenario, heat and drought could lead to energy shortages later in the summer, resulting in extreme conservation measures or blackouts. Diversifying the Northwest’s energy supply to include more renewable energy, like solar and wind power, would make the overall system more resilient to weather events and drought. 

To insulate Idaho’s salmon and steelhead against this climate crisis and ensure energy is secure and affordable, the most impactful action would be to breach the four dams on the lower Snake River, restoring it into a free-flowing river and lowering river temperatures. 

A solution to save wild salmon and steelhead exists. Congressman Mike Simpson’s Columbia Basin Initiative is a once-in-a-generation opportunity to support a bold and comprehensive proposal to restore Idaho’s salmon and steelhead to abundance while ensuring Idaho and Northwest communities a prosperous future. We encourage you to call or write to your elected officials – not only in Idaho, but also in Washington and Oregon – to urge them to support the Columbia Basin Initiative