One of the worst droughts in California's history has devastated more than a half-million acres of the most fertile farmland in America. In communities like Sacramento, "water police" go from door to door to enforce conservation measures. There's even a mobile "app" to report neighbors to city authorities so they can be fined for wasting water.

With the Sierra snowpack at 4% of normal as of May 20, Californians will desperately need what little water remains behind its dams this summer. Authorities have...