According to data from NASA’s Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) satellite mission, California experienced the largest water gain in two decades after years of intense drought and groundwater depletion. and the German Geneuk Research Center (GFZ). Last winter, gold water in atmospheric rivers reduced water shortages in the state during the last 10 years of drought, including the three driest years in California.

Think of the state’s central valley (yellow) as a giant swimming pool: Grace-FO’s measurements include all water found in the region’s lakes, rivers, soil, snow, and underground aquifers. From October 2022 to March 2023, storms delivered enough water to raise the amount of water in the pool by about 20 inches (about 500 millimeters). That’s roughly double the average winter water gain since satellite measurements of water storage began with the first GRACE mission in 2002.

The water increase between October 2022 and March 2023 can be seen in the maps above. Blue colors indicate regions where conditions are wetter than average (compared to 2004–2010), while red colors indicate drier-than-average conditions. The yellow line in the diagram below shows monthly fluctuations in the area’s water supply, highlighted in yellow on maps.

While the surface water pools are being filled, it can take years for the fresh water (aquifers) taken for irrigation and other needs to be completely renewed. “A nice winter with rain and snow doesn’t make up for years of extreme drought and widespread use of groundwater,” said Felix Lander, a researcher on the Grace-F project from the NASA reactive motion lab. The GRACE-FO team will continue to monitor how California’s water resources improve over the summer, after snow cover melts during the dry season and water levels in the state’s lakes, rivers and reservoirs begin to drop.

The observations were made possible thanks to the unique research approach used in both Grace missions. As water moves -ocean currents, rain, groundwater movement, ice etc. shaped – changes the mass of the planet near the surface, which changes the Earth’s gravity very slightly. GRACE-FO measures these subtle changes and allows researchers to estimate changes in total water volume in a given area.

Like its predecessor, the Grace-fo mission consists of two identical satellites flying one after the other. When a pioneer satellite passes over a region of greater mass, such as an area containing more water than another region, a slight change in gravity pulls it forward, increasing the distance between the two satellites. Microwave and laser instruments aboard the spacecraft accurately measure tiny changes in the distance between them, revealing details of the total mass of water that caused these changes. Source