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California's three-year drought has sparked a surge in demand for wells in the state's agricultural heartland. With federal and state allocations of surface water reduced to a trickle, growers are searching deeper underground for sources of water to keep their farms from ruin.

The clamor has overwhelmed California drillers and pump installers, forcing some farms to hire contractors from neighboring states.

It's also setting the stage for more problems later as groundwater supplies are shrinking faster than they can be replenished. In parts of the Central Valley, the water table has plummeted, drying up old wells and sinking the land above, a phenomenon called subsidence.

That's resulted in even deeper wells that cost hundreds of thousands of dollars to build and require more energy to pump water to the surface. As recently as two decades ago, a well several hundred feet would suffice. Today, large farms are drilling to depths of 2,000 feet in anticipation of falling water levels.

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