Speaking at a San Francisco news conference, Brown also called on "all citizens" to cut back "at least 20% of their water use." He was flanked by charts and photos showing the state's anemic precipitation and snowpack.
"We ought to be ready for a long, continued, persistent effort to restrain our water use," Brown said, adding that conservation efforts would be "voluntary."
Brown’s announcement, which lawmakers, farmers and activists have been urging for weeks, comes as state reservoirs are critically low and cities across the state have already begun water-rationing measures.
While Brown has downplayed the effect of an official drought declaration, those affected by the water shortage say it will be an important tool in focusing Californians on the problem.
The announcement came as Brown faced growing pressure to act. On Thursday, hundreds of activists from the Central Valley joined a bipartisan cadre of state lawmakers on the steps of the Capitol in Sacramento to urge the governor to take action.
During a recent two-day swing from Fresno to Bakersfield, Brown was asked about the water shortage at every stop. He met with farmers and agriculture leaders from the Westlands Water District in Fresno on Monday, and promised those in attendance that administration action would be forthcoming.