Last week, California Governor Jerry Brown announced his state’s first-ever mandatory water restrictions, in an effort to cope with four years of the worst drought in the state’s history.

The restrictions, under which cities and towns in the state were told to cut water use by 25 percent, could be the first step in what many researchers and analysts say is a fundamental change in the way California uses its diminishing water supplies. During the past year, National Geographic has reported extensively on the drought in California and on emerging water scarcity across the western United States, and shown how a warming climate and the lack of snow in the Cascades and Sierra Nevada mountain ranges have dramatically reduced snowmelt,