In the rich farmland of the San Joaquin Valley it's summertime -- peak growing season for many crops. But every sunbaked, scorching day brings another test of water reserves in a region running on empty.

The dearth of irrigation water from rivers or reservoirs has forced growers in the valley 80 miles north of Los Angeles to rely almost entirely on water pumped from wells.

"I'm worried from a couple of standpoints," said grower Stuart Woolf, as he stood in a field of tomatoes at harvest time. "One, I'm worried that we just flat run out of groundwater."

Some growers have already taken draconian steps to deal with the reality that they don't have enough water for all their crops. Near Fresno, Shawn Stevenson bulldozed a third of his orange grove.

"When these trees are gone they're not going to use any more water so I can put that water on another crop," Stevenson said.

In this third year of record drought, other growers have idled acreage for annual row crops.

"If this was a regular year, this would have been re-planted either to corn or to sorghum," said Tipton farmer Tom Barcellos, as he showed a reporter a field he's fallowed "either one of them would have been about 10 feet tall right at this point so we'd been walking here and you'd never see us."

Not far away, Vince and Pam Sola watched their almonds being harvested next door to a field they've left unplanted. Permanent tree crops are different. If you can't water them, you not only lose that year's income; you lose your investment.

"It's sad to see this land just lay there vacant," said Pam Sola, shrugging her shoulders as her husband finished her thought.

"Without surface water, we decided we had to leave some land idle and divert the water to less acres," said Vince Sola.

It is a summer of crisis for the Solas, Barcellos, and Woolf, but the crisis is hardly unique to them, with the drought stressing agriculture in virtually the entire San Joaquin Valley.

Its farming region stretches from the Tehachapi Mountains to Stockton, bounded by the Coast Range to the west and the Sierra Nevada to the east. Blessed with rich soil, an abundance of sun, but minimal rainfall even apart from drought years, the valley has relied for half a century on water imported from Northern California to become the nation's most productive growing region, known for its citrus and grapes. and increasingly for specialty tree crops such as almonds and pistachios, walnuts and cherries.

"This is an impact across the country," warned Barcellos. "You look at the number of nuts and grapes -- everything that's on somebody's table sometime of the day comes from this valley."

Barcellos is primarily a dairyman in a corner of Tulare County that produces 12 percent of the nation's milk. He worries about cows that need water every three hours, and rely on misters to avoid overheating in triple-digit temperatures.

"There is no surface water to buy here for this district," Barcellos laments, as he shows a reporter a bone-dry and dusty irrigation ditch that had been serving his farm for decades. He wistfully recalls playing in the ditch water as a teenager, even water skiing as a buddy pulled him along with a tractor. No more.

Since shortly after World War II, and with rare exceptions, the region farmed by Barcellos and the Solas has been able to rely on irrigation water from the federal Central Valley Project. The Bureau of Reclamation dammed the San Joaquin River, and diverted almost its entire flow into two irrigation canals for the eastside growers. A third canal, from the San Francisco Bay Delta to Mendota, was built for growers with rights to the San Joaquin River to replace the water no longer flowing downstream. Surplus water from the Delta Mendota Canal became available for growers including the Woolf Farm on the west side of the valley, and the region flourished, despite nagging concerns that in dry years, relying on junior rights, it would be the first to be cut off.

Statewide, agriculture takes an estimated three-quarters of the water California consumes. Farming is by far the state's largest single water user, dwarfing the amount city-dwellers use to boil their potatoes, brush their teeth, wash their clothes and water their yards.

Over the decades, periodic droughts have reduced or even interrupted deliveries, but nothing like this past year of drought, when only the holders of original, so-called "riparian" rights to the San Joaquin River received surface water; for other growers, the federal allocation was reduced to zero, leaving them almost entirely dependent on groundwater.

Not every farm has sufficient well capacity to serve all of its needs. In some cases, wells have gone dry as the water table is drawn down. Even farms with adequate well water see profits decimated by the cost of purchasing the electrical power needed to pump deep-lying groundwater hundreds of feet to the surface.

This past week, the California state legislature took initial steps toward tracking and eventually regulating groundwater withdrawals, a level of regulation to which some farmers are resistant, but others are resigned.

"We have to be saved from ourselves," said Vince Sola. "Otherwise we're just going to pump, pump, pump, and it will be all gone."

Using satellite technology, a new study by UC San Diego found 63 trillion gallons have been lost from the groundwater reserves of the western U.S. That's enough to cover all the land west of the Rockies in four inches of water, the authors noted. As reserves drop, wells go dry, and drillers cannot keep up with the demand for drilling deeper.

"We're 12-13 months behind," said Steve Arthur of Arthur & Orum Well Drilling, as he watched his crew go down 600 feet for a new well to supply an almond grove outside Caruthers. In another area to the north of Fresno, another grower had Arthur dig down 2,000 feet. The water table is not yet that low, Arthur explained, but the grower wants reserve room as the groundwater is drawn down further.

Wells that deep cost as much as $750,000, Arthur said, not including the pump and other expenses before the well becomes operational.

It's deja vu.

Before the Central Valley Project and California's State Water Project, San Joaquin Valley growers relied almost exclusively on groundwater. So much was pumped out, that the floor of the valley began dropping, or "subsiding," as the weight of the ground above crushed the waterless Earth below. By 1977, the ground near Mendota had subsided some 30 feet, according to a study by the U.S. Geological Survey.

That subsidence has again reared its head is not disputed by growers.

"In some regions you can actually see the ground around the well site -- it looks like the well is growing -- it's coming out of the ground," said Woolf, explaining that in reality, the ground is dropping around the wellhead, exposing more of it.

To stetch their water, growers have been switching to more efficient irrigation techniques, including expensive drip systems.

It has also lead to unintended consequences. Drip means that the mineral contaminants in groundwater are concentrated at the seed row. Avoiding overwater also limits the water that in the past would have percolated through the soil to replenish the underground water table.

Where the drought is reducing crop yields may lead to higher prices -- but not necessarily for crops in competition with other regions, and the California drought impact at the grocery checkout stand so far has been minimal.

"If all you know is you go to the store and the food is there and it doesn't cost any more, then you don't seen the impact," Pam Sola said.

Growers hope it does not get to that point before they get assistance. They are calling for the government water projects to build additional storage, so that more of the snowmelt and river runoff during wet years can be saved for drought years.

Some $2.7 billion would be dedicated to new storage if California voters approve the water bond that the legislature has placed on the November ballot. Many growers think it should be more.

In addition, growers bristle at environmental conservation rulings and decisions that have placed limits on the amount of river water that can be withdrawn and delivered by the water projects for irrigation.

Some characterize the dispute as Farmer vs. Fish.

Of particular concern are the salmon that swim through the vast Delta where the San Joaquin and Sacramento Rivers reach the San Francisco Bay. Salmon still spawn upstream in the Sacramento Rivers. Federal rulings have effectively placed limits on water releases from upstream dams in order to insure that river temperatures remain cool enough for salmon to spawn.

Under a separate agreement to restore the salmon runs in the San Joaquin River, 17 percent of the average flow long diverted to irrigation canals will be again sent downstream for the fish.

The agreement does recognize the impact of periodic droughts. This year, no water is being released into the San Joaquin River for restoration, according to Monty Schmitt of the Natural Resources Defense Council (NRDC).

That is not the only impact of the drought on environmental restoration. It has also limited the amount of water for the San Luis National Wildlife Refuge in an area that once was periodically flooded by the San Joaquin River and was a natural wetland. That ended when 19th century ranchers established grazing fields and built levees to protect them.

The value of maintaining wetlands and native grasslands became a goal of the US Dept. of the Interior after it became apparent that one of the worst natural disasters of the 20th century, the Oklahoma Dust Bowl, was enabled by the removal of native grasslands for farm crops that could not be sustained during a drought.

Since the 1960's, some of the water delivered by the Delta Mendota Canal has gone to flooding

the Refuge every September. This drought year, the allocation has been reduced to 65 percent of normal, according to Karl Stromayer, Refuge Asst. Manager, and that will affect the habitat in this portion of what is known as the Pacific Flyway.

"When migratory birds get here, we have less food for them," Stromayer said.

Ironically, during this drought summer there is now more water in the San Joaquin than there has been for decades, because it is being released to satisfy the riparian rights of downstream properties that for decades until this year had been served by the Delta Mendota Canal.

That water is being released from Friant Dam, rather than being diverted into the Friant-Kern canal, is the reason Barcellos and his fellow Tulare County growers are not receving any Central Valley project water this year.

Growers acknowledge the need to protect habitat, but challenged the benefits of how it has played out. A longtime sore point for growers is a ruling that effectively limits how much freshwater can be

withdrawn from the Delta in order to protect a finger-size fish known as the Delta Smelt, an endangered, and therefore protected, species.

Woolf observed the hand-wringing in Los Angeles in July when a water main failure sent 20 million gallons of water through the UCLA campus en route to storm sewers.

"Here this season over one 60 day period we sent 260 million gallons under the Golden Gate Bridge for a benefit nobody knows what it was," complained Woolf.

Environmental activists contend there are tangible benefits.

"It's very shortsighted to wipe out fisheries to get a little water now that does not benefit us in the longrun," said Kate Poole, senior attorney with the NRDC.

Regardless, the battle will continue to be fought in court.

The environmental issues have had less impact on farming regions in the Delta, and to the north in the Sacramento Valley, where growers rely on water districts with riparian rights to the Sacramento River, which delivers are more than the San Joaquin. Growers in California's next largest agricultural region, the Imperial Valley near the Mexican border, import their water from the Colorado River, which has been less affected by the California drought.

All with stakes in California's water supply worry about the effect of climate change adding to unpredictability. But as it is, California's surface water resource has been frustratingly unpredictable since epic flooding overwhelmed the San Joaquin Valley's first generation of farmers back in the 19th Century after the Gold Rush.

It's been four decades since a drought as severe as the current one, but since 1977, not a decade has passed without a drought, and the one just 5 years ago triggered conservation responses still in place in many areas, including Los Angeles.

By the same token, every 4 years on average there is a rainy season wet enough to produce flooding. The last one occurred in the winter of 2011, when reservoirs ran out of capacity and instead of banking water for summer during winter and spring, had to release it.

"We never get an average amount of water," Schmitt said. "It's always too much or too little. The key is: how do we manage it so we will have vibrant agriculture industry, while also having a healthy river and community resource."