May 5, 2015:

The California State Water Resources Control Board unanimously approved the water restrictions announced by California Governor Jerry Brown on April 1, 2015.

Emergency 25% cut in California cities' water use approved | Los Angeles Times

Apr 1, 2015:

California Governor Jerry Brown issued Executive Order B-29-15 which directs the California State Water Resources Control Board to reduce potable (safe to drink) water usage throughout the state of California by 25% through February 28, 2016, the first time ever that mandatory water restrictions have been imposed in the state of California.

Brown orders California's first mandatory water restrictions: 'It's a different world' | Los Angeles Times

More:

• As water runs dry, Californians brace for a new way of life | The Washington Post
• California Drought Tests History of Endless Growth | The New York Times