Fields of carrots are watered March 29, 2015, in Kern County, Calif. Subsidized water flowing in federal and state canals down from the wet north to the arid south helped turn the dry, flat plain of the San Joaquin Valley into one of the world's most important food-growing regions. Frederic J. Brown/AFP/Getty Images hide caption

itoggle caption Frederic J. Brown/AFP/Getty Images

Morning traffic makes its way toward downtown Los Angeles along the Hollywood Freeway, past an electronic sign warning of severe drought. California Gov. Jerry Brown introduced the state's first mandatory water reduction measure this week. Richard Vogel/AP hide caption

itoggle caption Richard Vogel/AP