As federal officials negotiate new rules for sharing the Colorado River's shrinking water supply, scientists are expanding efforts to better measure one of the basin's biggest sources of water loss: evaporation.
The Desert Research Institute in Reno, Nevada, is installing floating weather stations directly on major Upper Colorado River reservoirs to collect more accurate measurements of the conditions that drive evaporation.
Researchers say improving evaporation estimates could give water managers better information as they make difficult decisions about the future of the Colorado River, where years of drought, warming temperatures and heavy demand have strained water supplies.
The project is a partnership between the Desert Research Institute, the Upper Colorado River Commission, and the U.S. Bureau of Reclamation. This summer, researchers are establishing new monitoring stations at the Flaming Gorge, Blue Mesa, and Navajo reservoirs.
The effort builds on a monitoring project at Lake Powell that has collected evaporation data since 2019, making it one of the longest-running reservoir evaporation studies in the Western U.S.
"This project places our monitoring equipment in the middle of the reservoir to provide a cleaner picture of air temperature, humidity, wind speed over the water, as well as the water temperature signal at the center of the water body," said Chris Pearson, a hydrologist with the institute.
Unlike traditional weather stations located along reservoir shorelines, the new instruments sit on floating platforms directly over the water. That gives researchers a more representative picture of the weather and water conditions that influence evaporation.
Pearson said researchers will combine those field measurements with data from OpenET, a satellite-based platform that estimates how water moves from the land into the atmosphere.
"Improved estimation of the timing and the magnitude, specifically for reservoir evaporation, will strengthen our water budget estimates and support really data-driven water management strategies," Pearson said.
Measuring reservoir evaporation is not new, but long-term monitoring over open water remains limited. The Desert Research Institute has also led other evaporation monitoring and modeling efforts, including the Bureau of Reclamation's Open Water Evaporation Network Initiative and projects in Texas.
Scientists say more accurate evaporation estimates won't solve the Colorado River's water challenges. They could, however, reduce uncertainty about how much water is leaving the basin's largest reservoirs, helping water managers make decisions with better information as they negotiate new operating rules for a river that supplies water to about 40 million people across the West.
This story was produced by the Mountain West News Bureau, a collaboration between KUNR, Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNC in Northern Colorado, KANW in New Mexico, Colorado Public Radio, KJZZ in Arizona and NPR, with additional support from affiliate newsrooms across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting and Eric and Wendy Schmidt.
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