California has been recovering from 5 years of drought since the end of last year. But this giant reservoir was still struggling. It had dwindled to a weedy channel at just 7 percent of capacity and was perilously close to being written off as a regional water supply. And then came one of the largest storms in memory on February 17 swamping historical records and causing Lake Cachuma—120 miles northwest of Los Angeles and once a poster child of the drought—to rise a whopping 31 feet in depth in just a few days.