Rivers In Flux
Colin Gleason, associate professor and Armstrong Professional Development Professor in civil and environmental engineering, leads the research group Fluvial@UMass, an interdisciplinary team studying rivers, climate change, and Arctic hydrology through field work, remote sensing, and modeling/machine learning efforts.
At the heart of Gleason's work is a focus on how rivers are shifting—particularly concerning flooding, sediment transport, and water availability.
Gleason was recently part of a research team that found that rapid glacier melt caused by global warming has doubled the number of rivers in the Himalayan region over the past decade. Using satellite observations and computer models from 2004 to 2019, the team reported that 11,113 rivers experienced an increase in river discharge (the amount of water flowing through them at any given time). This surge in river volume has affected major rivers such as the Indus, Yangtze, Amu Darya, and Syr Darya. Such drastic changes in river patterns pose a challenge for billions of people in China, India, and Southeast Asia who depend on it for drinking, agriculture, and generating electricity.
City planners will need to consider these shifting water patterns because glacial water has been more seasonally predictable than precipitation. “The real effect is: It changes the stability of how much water is coming into your hydro system,” Gleason says. “If you’re building a drinking water or hydropower system reliant on glaciers providing a stable water supply, are you ready for that stable supply to change, and will the glacier even still be there 100 years from now?”
That study, published in AGU Advances, was first-authored by Jonathan Flores, a 2025 doctoral graduate in Gleason’s Fluvial@UMass research group.
Gleason collaborated with another Fluvial@UMass doctoral graduate, Craig Brinkerhoff, to publish a paper in Science that shed light on an urgent regulatory challenge.
Ephemeral streams are defined as seasonal or intermittent streams that only flow in response to rain—and, following a 2023 Supreme Court ruling, they are no longer protected under the Clean Water Act. Gleason and Brinkerhoff modeled the contribution of these ephemeral streams to river systems across the U.S., ultimately revealing that they supply, on average, 55% of the water flowing out of major river systems—meaning that pollution in these “hidden” channels may end up in major watersheds well downstream, despite remaining unregulated. This paper was highlighted in major media outlets including the New York Times.
In another paper, also recently published in Science, Gleason and former Fluvial@UMass postdoc Dongmei Feng used satellite data and modeling to estimate river discharge across some 3 million stream reaches over a 35-year period. They found that large, downstream rivers have experienced annual flow decreases in 44% of locations, while in small, upstream rivers, 17% saw increases. The implications of these findings are profound: declining flow downstream threatens freshwater supply, irrigation, hydropower, and delta formation, while surging flow upstream contributes to a 42% rise in flood events in headwater streams.
“People who live along these rivers, of course, know there are problems,” reflects Gleason. “But if you’re a policy analyst and you’re trying to determine the best location for a new hydropower plant out of 100 candidates, it’s hard to measure 100 different rivers accurately. [Colleagues in water systems say] you would be shocked at how many places, particularly those that are resource-limited, make major decisions about climate futures, water resources, and infrastructure projects with almost no data on hand. My hope is that everyone can use these data, understand them, and maybe make a more informed decision.”
Gleason’s expertise extends to the global stage through his long-standing role in NASA’s Surface Water and Ocean Topography (SWOT) mission. SWOT is the first satellite to map the height, width, and slope of nearly every river wider than 50 meters and millions of lakes worldwide. Having worked on the project since his PhD days, Gleason now serves as lead academic scientist for calibration and validation of U.S. inland hydrology and co-lead for discharge production. He directs field campaigns to verify SWOT’s measurements, and he created and helps run international software on behalf of NASA that converts raw satellite readings into river discharge estimates. The resulting data is revolutionizing flood mapping and water resource assessment by offering an unprecedented global view of surface water.
By combining SWOT’s sweeping observations with the detailed modeling and field research of Fluvial@UMass, Gleason is helping close crucial gaps in understanding—and predicting— how rivers and floods will behave in a changing climate.