The Great Salt Lake Basin, a dry region in the Western U.S., depends heavily on underground water, known as groundwater. With persistent drought and high demand, these critical water supplies are shrinking. Accurately measuring this water loss is vital for managing our resources.

To do this, we used data from NASA's GRACE satellites, which track tiny changes in Earth's gravity to measure shifts in the region's total water storage from 2002 to 2025. To isolate just the groundwater, we first subtracted all the other water components, like water in lakes, reservoirs, snowpack, and soil. Even after this, the satellites' broad, low-resolution view tends to underestimate water loss in specific areas where pumping is heaviest.

To get a more precise number, we compared our satellite estimate to direct measurements from over 1,000 local groundwater wells. We discovered the satellites were underestimating the actual groundwater loss by about half. By doubling the satellite's estimate, the results finally matched the on-the-ground data. This improved method gives us a reliable way to track changes in our region's most important water source