California Governor Jerry Brown has declared a drought emergency, a move that will allow the parched state to seek federal aid as it grapples with what could turn out to be the driest year in recorded state history.
The dry year California experienced in 2013 has left reservoirs with a fraction of their normal reserves and slowed the normally full American River so dramatically that brush and dry riverbed are showing through in areas normally teeming with fish.
"We can't make it rain, but we can be much better prepared for the terrible consequences that California's drought now threatens, including dramatically less water for our farms and communities and increased fires in both urban and rural areas," Brown said.
"I've declared this emergency and I'm calling all Californians to conserve water in every way possible."
The move will allow him to call for conservation measures and provide flexibility in deciding state water priorities.
Brown said the drought threatened to leave farms and communities with dramatically less water and increased the risk of fires in urban and rural areas.
The dry spell has already left huge swaths of tinder-dry forest vulnerable to going up in flames.
On Thursday, a massive blaze raged just outside Los Angeles, damaging several homes and forcing residents to evacuate the area, where the fire risk had been elevated for weeks.
Brown appealed to residents to keep a lid on water use with the aim of reducing overall consumption by 20 per cent, saying "this takes everybody pitching in". He warned that mandatory conservation programmes may have to be initiated.
In a sign of the severity of the drought, some of the state's reservoirs are at their lowest levels in years.
The Folsom Reservoir near Sacramento is so low the remains of a Gold Rush-era ghost town - flooded to create the lake in the 1950s - are visible for the first time in years.
The mountain ranges, where run-off from melting snow provides much of the water for thirsty cities and farms, have just 20 per cent of the snow they normally have at this time of year.
Lake Shasta, the largest reservoir in California, is down from its historical average by nearly half, holding just 36 per cent of the water it is built to contain.
For the state's US$44.7 billion agriculture business, water scarcity is a problem made worse by a recent switch to orchard-style crops such as almonds and olives. Unlike vegetables or cotton, which grow in fields that can be left fallow in dry years, the trees need water every year.