We’ve had a very hot July, and while it looks like our heat wave has finally ended for now, I wanted to show you how water temperature in our river reacted to the very hot days. Parts of the Spokane River are very hot, reaching some of the hottest temperatures we’ve seen, while others remain cool. Why? Read on.
As you can see above, the water temperature gage upstream of Harvard Road is very hot, reaching more than 80 F. This is in an area that loses water to the aquifer, a “losing reach” that only contains surface water. In contrast, the Peaceful Valley temperature only reaches 67 F. That is because cool ground water enters the river and cools our water. But why does the Peaceful Valley temperature drop when the Spokane Valley gage rise?
It’s because the river flow is dropping, increasing the proportion of cool groundwater to warm surface water! Neat! Our local redband trout think so. This phenomenon allows them to survive in parts of our river. They certainly can’t live in the Spokane Valley, in the losing reach of the river.
That’s because the high temp in the valley reached 82.8 F this week! Our water temperature standard in Washington State, designed to protect our trout and salmon is 64.4 F!