FRESNO, Calif. (AP) - For decades, this city in California's agricultural heartland relied exclusively on cheap, plentiful groundwater and pumped increasingly larger amounts from an aquifer as its population grew.
But eventually, the water table dropped by more than 100 feet, causing some of Fresno's wells to cave in and others to slow to a trickle. The cost of replacing those wells and extracting groundwater ballooned by 400 percent.
"We became the largest energy demand in the region - $11 million a year for electricity just to run the pumps," said Martin Querin, manager of the city's water division, which supplies 550,000 residents.
Fresno is just one player in a water war that's quietly being fought underground. Throughout the Central Valley - one of the world's most productive agricultural regions - farmers, residents and cities have seen their wells go dry. Those who can afford it have drilled deeper wells that can cost hundreds of thousands of dollars.
Experts say water supplies have been strained by growing city populations and massive tracts of newly planted orchards and vineyards.
"Water levels are dropping dramatically in some areas. It's never been this bad," said Steve Arthur, vice president of Arthur and Orum Well Drilling.
The drops create concerns that groundwater is becoming unaffordable and that overuse could cause serious land subsidence, which can damage infrastructure such as roads.
"We can't keep over-pumping groundwater," said Peter Gleick, president of Pacific Institute, a nonpartisan research group in Oakland. "It's simply unsustainable and not economically viable in the long run."
California has few rules governing groundwater. While some basins limit pumping through management plans or court rulings, anyone can build a well and pump unlimited amounts in most of the state.
The U.S. Geological Survey has found in much of California - the San Joaquin Valley, the Central Coast and Southern California - more water has historically been pulled out of the ground than was replenished.
Climate change and droughts are putting additional pressure on aquifers, said USGS hydrologist Claudia C. Faunt. There also is a recent shift among California farmers to replace row crops such as tomatoes with orchards, which can't be scaled back in dry times.
On the west side of the Valley, massive farms whose surface water deliveries have been severely curtailed to protect fish in the Sacramento-San Joaquin Delta are increasingly relying on groundwater and digging deeper wells.
Farmers have also seen wells go dry east of Modesto in the Sierra foothills, where they've planted hundreds of thousands of acres of new orchards. They've been forced to drill new wells as deep as 800 feet.
"There are more straws taking water out of the basin," said Al Rossini, a third generation farmer from Oakdale.
And whoever has the longest straw - and the deepest pockets - is winning.
Some small farmers can't afford to drill deeper. Rural residents who rely on smaller wells for drinking, cooking and bathing are also feeling the brunt.
"Our well went dry, and we had to redrill," said Gerald Vieira, a retired Denair resident. Vieira paid $13,000 this summer for a new well - drilled 200 feet deeper than it had been before. A dozen of his neighbors also bought new wells.
Some farmers and urban districts are now trying to find solutions to prevent groundwater overuse.
Fresno plans to use a combination of surface, ground and treated wastewater and to greatly expand the city's program to replenish groundwater, and farmers in the Sierra foothills also plan to dig recharging ponds.
Meanwhile, many farmers and other water users say the state must build more storage, especially groundwater banks, to hold water during wet years.
"Water is like blood to the body," said Rossini. "Without water, California won't be the same state."