Water is so commonplace that we often take it for granted. But too much—or too little of it—makes headlines. Catastrophic flooding in the U.S. Midwest this spring has caused billions of dollars in damage and wreaked havoc with crops, after rain tipped off a mass melting of snow. Seven years of California drought so debilitating that it led to water rationing came to a close after a wet and snowy winter capped off several years of slow rebound and replenished the vital mountain snowpack.