At Harris Farms in California's Central Valley, it's not hard to discern the effects of the state's drought. Fields that in previous years would have been lined with tomatoes or broccoli now contain nothing but brown earth.
About two-thirds of the farm's 5600ha are fallow, and for the first time since it started growing salad leaves three decades ago, the farm hasn't planted a single lettuce.
In a normal year, said executive vice-president William Bourdeau, Harris Farms plants 1400ha of lettuce. "On a good yield that translates to three million cartons of lettuce.
"And each carton contains 24 head of lettuce, which equates to around 72 million head of lettuce that we didn't grow and put into the market this year. And that's just one of our crops. And we're just one farm."
California grows almost 70 per cent of America's lettuce, which has gone up in price more than any other fruit or vegetable this year. The US Department of Agriculture estimated last week that fresh fruit and vege prices would rise by 6 per cent this northern summer.
The three-year drought afflicting America's Southwest has already affected California's farming communities, but it's now beginning to be felt by consumers in the US and beyond. In 2013 less rain fell on California than in any year since it achieved statehood in 1850. The region's rivers and reservoirs are at their lowest ebb ever. At the state capitol in Sacramento, the lawns have been allowed to grow brown, while the Getty Museum in Los Angeles recently drained its water features and turned off its fountains.
But the drought is most deeply felt in the Central Valley, California's agricultural backbone. The state's US$45 billion ($51.3 billion) farming industry produces almost half the fruits, vegetables and nuts grown in the US, and to do that it uses 80 per cent of California's water. Almonds alone account for 10 per cent of water use, not surprising given that California produces 80 per cent of the world's almonds.
With water becoming more and more expensive, farmers in California have allowed 202,300ha of land to lie fallow this year. Roadside signs up and down the Central Valley read: No Water = No Jobs, and No Water = Higher Food Costs.
Driving through the Central Valley on Interstate 5, the casual visitor might consider the arid landscape an unlikely agricultural zone. But a closer look reveals the valley is criss-crossed with canals bringing surface water from the Sierra Nevada mountains to irrigate the high-quality soil which, combined with long, hot summers, makes a highly fertile region.
But the Sierra Nevada snowpack was less than 30 per cent of its normal size this spring. In 2013 the federally run Central Valley Project allocated farmers a 20 per cent share of the water the canals carried. This year they got nothing. Many have resorted to drilling ever deeper for groundwater, a practice as controversial as it is expensive.
Farmers blame their water woes in large part on what John Harris, the chief executive of Harris Farms, describes as "unreasonable" environmental restrictions. "We'd like to see more attention paid to human needs versus the fish needs," Harris said.
In February, the Obama Administration announced a US$200 million drought aid package for California. But that will be of little use in combating the effects of what some scientists fear may be a "mega-drought", lasting as long as 200 years.
So what will California's farms do if the present conditions continue, or worsen? As Bourdeau put it: "I'm not sure how you have a farm, if you don't have any water."