Over and over again we are reading about science scratching its head and wondering what can be done for our heating drying rivers across the west. I’ll give them a hint. One answer comes in a furry package with a flat tail.
Heat waves in U.S. rivers are on the rise. Here’s why that’s a problem
The temperature spikes can cause trouble for fish, plants and water quality
U.S. rivers are getting into hot water. The frequency of river and stream heat waves is on the rise, a new analysis shows.
Like marine heat waves, riverine heat waves occur when water temperatures creep above their typical range for five or more days (SN: 2/1/22). Using 26 years of United States Geological Survey data, researchers compiled daily temperatures for 70 sites in rivers and streams across the United States, and then calculated how many days each site experienced a heat wave per year. From 1996 to 2021, the annual average number of heat wave days per river climbed from 11 to 25, the team reports October 3 in Limnology and Oceanography Letters.
Gee that sounds bad. The water is getting hot hot hot. That’s rotten for the fish who need it cooler like salmon and trout. I wish there was something we could do to help. Anything at all…
The study is the first assessment of heat waves in rivers across the country, says Spencer Tassone, an ecosystem ecologist at the University of Virginia in Charlottesville. He and his colleagues tallied nearly 4,000 heat wave events — jumping from 82 in 1996 to 198 in 2021 — and amounting to over 35,000 heat wave days. The researchers found that the frequency of extreme heat increased at sites above reservoirs and in free-flowing conditions but not below reservoirs — possibly because dams release cooler water downstream.
Huh. Dams make the water cooler. Who knew. Gosh I wish there was some kind of dam-making creature that could just build them in all our waterways all across those hot streams…I mean like a dam-o-matic but one that could replenish itself and keep working even when things were hard. It would have to be a vegetarian too, because we don’t want it to eat those fish we’re trying to save, right?
There are chemical consequences to the heat as well, says hydrologist Sujay Kaushal of the University of Maryland in College Park who was not involved with the study. Higher temperatures can speed up chemical reactions that contaminate water, in some cases contributing to toxic algal blooms (SN: 2/7/18).
The research can be used as a springboard to help mitigate heat waves in the future, Kaushal says, such as by increasing shade cover from trees or managing stormwater. In some rivers, beaver dams show promise for reducing water temperatures (SN: 8/9/22). “You can actually do something about this.”
