Spencer Tassone, a doctoral candidate in environmental sciences who graduates this spring, studies the effects of extreme temperatures on rivers and other less-studied bodies of water. His research has determined that river heat waves are increasing in frequency.
“My study provided evidence that heat waves are associated with times of low water volume, such as during a drought,” Tassone said.
Although heat waves are largely associated with summer and fall, the most extreme river heat waves happen between December and April, he found.

Tassone has been interviewed in various media about his research. This screengrab is from a self-made video for the UVA Coastal Research Center.
Related to his findings, Tassone recently won UVA’s Rath Public Service-Focused Research Award. He also is co-author of a technical report for the Chesapeake Bay Program on rising watershed and bay temperatures and was interviewed live on Fox Weather.
He spoke to UVA Today about the threat of a changing climate on our waters, including to fish, and the implications of his research for future waterway management.
Q. Why are these river heat waves occurring?
A. Riverine heat waves across the U.S. are on the rise due, in part, to increasing atmospheric temperatures and low-flow conditions associated with climate change and other manmade causes.
Q. Can you explain why the most extreme heat waves happen during colder weather?
A. People typically associate heat waves with summer, as this is when temperatures are greatest. However, aquatic heat waves are often defined based on the water temperature being above a certain threshold for the season and for a minimum duration of five days. This allows us to identify extreme temperature conditions at any time of the year.