Satellite Measurements Show Slight But Steady Declines In Heights Of 41 Dams In 13 States & Puerto Rico

The satellite signal was subtle but persistent. A decade of observations suggested that part of the Livingston Dam — a 2.5-mile-long earth and concrete structure about 70 miles north of Houston — was sinking by roughly 8 millimeters per year. This deformation could indicate the structure is unstable, said geophysicist Mohammad Khorrami, who presented the findings in December at the annual meeting of the American Geophysical Union. Though the observation is preliminary, he said it was cause for concern; regulators consider the dam to have “high hazard potential,” meaning it could lead to deaths and significant property damage if it ever failed.

Livingston is not the only U.S. dam that appears to be sinking into the earth, said Khorrami, a postdoctoral associate at Virginia Tech. Using radar from satellites to survey hydropower dams in 13 states and Puerto Rico, he and his colleagues detected subtle shifts in the height of all 41 structures they studied. The observations ranged from barely perceptible subsidence to more worrying “differential settlement” — cases like the Livingston where parts of the dam are moving at varying rates.

The team’s findings don’t necessarily indicate that downstream communities are in immediate danger, cautioned Manoochehr Shirzaei, a fellow Virginia Tech geophysicist who contributed to the research. There can be benign explanations for small changes in a dam’s elevation, and the dams must be inspected in person to determine whether the satellite detections are a sign of cracks or other structural issues.

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According to the Association of State Dam Safety Officials (ASDSO), there are nearly 92,000 dams in the United States, ranging from behemoths like the Hoover Dam to more modest earthen structures used to hold back reservoirs, tailings ponds and other small water bodies. The majority of these dams are more than 50 years old — an age at which many structures begin to show signs of wear and tear. The research presented last week has not yet been published in an academic journal. But it uses the same methodology as other peer-reviewed studies, including an analysis of a deadly 2023 dam collapse in Libya that Shirzaei published in 2025.

The Virginia Tech researchers focused their analysis on large hydropower dams that are classified as being in poor or unsatisfactory condition and that could cause fatalities if they failed. Any weaknesses in these structures could make them vulnerable to severe weather fueled by climate change, Shirzaei said. A Washington Post investigation found that the flow of water vapor through Earth’s atmosphere — a crucial ingredient for extreme rainfall — is on track to hit a record high for 2025. Increasingly intense rain events can rapidly fill reservoirs and put dams under unprecedented strain, experts say.

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https://www.washingtonpost.com/climate-environment/2025/12/30/us-dams-sinking-risks/