SerpApi.Org
A team of Virginia Tech geoscientists has found a new way to examine the widespread effects of dams on river temperatures: using Landsat thermal infrared imagery to gather data on rivers across the United States. By using satellite imagery instead of site-specific, on-the-ground measurements, researchers can draw from a much larger pool of data.
Subscribe to our newsletter for the latest sci-tech news updates.
"Studying river temperatures up- and downstream of dams has been done before, but on 10 dams or fewer total," said George Allen, associate professor of hydrology and remote sensing in the Department of Geosciences. "We've expanded this to more than 250 dams, so we're getting much more of a large-scale understanding of what's happening with river temperatures and dams."
The study, recently published in Science Advances, tracked water temperatures upstream and downstream of more than 250 of the largest dams in the United States from 2013–24.
Measuring thermal impact
Due to limitations of satellite image resolution, the research team targeted dams on U.S. rivers greater than 100 meters (330 feet) wide. In addition, the dams had to cross the entire river, creating a large obstruction. Thermal imaging was then used to create river surface-temperature profiles extending both upstream and downstream.
The research findings echoed what previous studies have demonstrated: Dams alter downstream temperatures. In fact, temperature differences were found in 71% of the study's observations.
However, the data also showed that differences could vary based on dam type or season. Temperature variations may also be smaller in scale than previous studies have shown.
"A lot of the studies that are looking at single dams are looking at dramatic downstream impacts. For example, something like the Three Gorges Dam in China is a very large dam that has very large effects," said Emily Ellis, Ph.D., '26.
"By grabbing a large portion of the dams in the U.S., we can see finer-scale differences, not just these large impacts."
Why temperature matters
Temperature, one of the core parameters of water quality, is fundamental to a river's ecosystem health and biochemistry. For example, water that is too warm can encourage the growth of algal blooms, which deplete oxygen and produce toxins. Thermal fluctuations can throw off the timing of natural processes like fish spawning, which is driven by temperature cues.
"It's important to know the impact that those dams are having, because in so many cases, dams are primarily managed for water movement and not temperature," said Ellis, now a postdoctoral researcher at the University of North Carolina at Chapel Hill. "They're thinking about preventing flooding, generating power—those kinds of things—and temperature is just a leftover piece."
Why scope matters
Allen said that in the field of hydrology, research has progressed to a global scale to determine how water systems react to climate change and land-use change. But many of these studies have focused on warming temperatures in lakes. There haven't been many studies focusing on river temperatures on a large scale.
By introducing satellite imagery as a tool to study rivers on a broader scale, scientists can gain a better understanding of the effects of dams and their implications for freshwater ecology and water resource management.
While this particular study focused on the impacts of dams, satellite imagery could also be used to investigate the effects of other manmade structures on river temperatures.
"This approach doesn't just apply to dams," said Allen. "We could be looking at other things, like power plants or data centers potentially warming rivers. I think we can use this automated technique and apply it to other systems as well."
More information: Emily A. Ellis et al, Satellite observations reveal widespread alteration of river thermal regimes by US dams, Science Advances (2026). DOI: 10.1126/sciadv.aeb5193
Provided by Virginia Tech
This story was originally published on Phys.org.
