What happens when your water supply runs dry? You go underground. In some parts of California, drought-plagued farmers are digging groundwater wells that plunge deeper and deeper into the earth, siphoning away the water of their neighbors, and causing the ground to collapse—potentially destroying the soil for good.

A story in the New York Times’ drought series explores how groundwater used to be a last resort—a backup resource to tap only if things got tough. After a few dry years, farmers have needed to start drilling. But one of the biggest issues within California’s larger water data problems is that up until last year there was no groundwater regulation at all. Even now it will take a few years for the limited legislation to go into effect. This is exceptionally problematic during a drought, says Jay Famiglietti, senior water scientist at the NASA Jet Propulsion Laboratory, where scientists have been measuring the groundwater depletion by satellite:

“You drill a well on your property, you draw it out, even if it means you draw from under your neighbor’s property,” he says. “You’re drawing water from every direction.”

Underground water supply isn’t fenced or restricted; it is moisture held in the soil, rocks and clay, and drawn through wells like soda through a straw.

In a normal year, Mr. Famiglietti says, 33 percent of California’s water comes from underground, but this year it is expected to approach 75 percent. Since 2011, he says, the state has lost eight trillion gallons from its overall water reserves, two-thirds of that from its underground aquifers.

But as the aquifers are drawn down, the normally saturated porous earth around them starts to dry out, which causes the layers of soil to compact. Not only does the ground at surface level start to sink, it actually collapses into the aquifer. This is called subsidence, and it can actually ruin the water table forever.

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Some parts of the Central Valley of California have seen the ground sink up to a foot over the last few years, according to a map created for the story.

Even more frightening is the fact that this is actually happening in many places, not just California. Unmonitored drilling of freshwater sources can happen anywhere, and even massive aquifers in areas flush with rain are in danger of being overdrawn. The biggest water wars of the future are more likely to be invisible battles waged underground.

[New York Times]

An 800-foot groundwater well is being dug for an almond farm in California, AP Photo/Scott Smith