Each spring and summer, meltwater runoff from Sierra Nevada snowpack helps replenish rivers and reservoirs, while also recharging the groundwater. About three-fourths of the state’s precipitation in an average year falls as snow and rain in Northern and Central California—mostly the Sierra Nevada. The time-lapse series of images above shows springtime snow-covered area on the Sierra Nevada from 2006 to 2021. Hatchett has also been studying changing snow levels—the line of elevation above which more precipitation falls as snow than rain—in the Sierra Nevada. How the boom-and-bust snow cycles in the Sierra Nevada will play out as the world warms remains to be seen.