Tuesday June 18, 2024
NASA via Maven’s Notebook —
Record snowfall in recent years has not been enough to offset long-term drying conditions and increasing groundwater demands in the U.S. Southwest, according to a new analysis of NASA satellite data.
Declining water levels in the Great Salt Lake and Lake Mead have been testaments to a megadrought afflicting western North America since 2000. But surface water only accounts for a fraction of the Great Basin watershed that covers most of Nevada and large portions of California, Utah, and Oregon. Far more of the region’s water is underground. That has historically made it difficult to track the impact of droughts on the overall water content of the Great Basin.
A new look at 20 years of data from the Gravity Recovery and Climate Experiment (GRACE) series of satellites shows that the decline in groundwater in the Great Basin far exceeds stark surface water losses. Over about the past two decades, the underground water supply in the basin has fallen by 16.5 cubic miles (68.7 cubic kilometers). That’s roughly two-thirds as much water as the entire state of California uses in a year and about six times the total volume of water that was left in Lake Mead, the nation’s largest reservoir, at the end of 2023.
While new maps show a seasonal rise in water each spring due to melting snow from higher elevations, University of Maryland earth scientist Dorothy Hall said occasional snowy winters are unlikely to stop the dramatic water level decline that’s been underway in the U.S. Southwest.