On April 1, California Governor Jerry Brown stood in a Sierra Nevada meadow atop parched, brown grass — at an elevation of 6,800 feet, where there would normally be five feet of snow at that time of year — and announced the state’s first-ever mandatory water restrictions.The Golden State is still in the grip of a severe drought that began in 2012, and new research suggests it is one of the worst in centuries.The day Gov. Brown announced the statewide water restrictions, snowpack in the Sierra Nevadas was reported to be at just 5 percent of its historical average, as calculated from records dating back to the 1930s.