Aquifers provide us freshwater that makes up for surface water lost from drought-depleted lakes, rivers, and reservoirs. We are drawing down these hidden, mostly nonrenewable groundwater supplies at unsustainable rates in the western United States and in several dry regions globally, threatening our future.
We are at our best when we can see a threat or challenge ahead. If flood waters are rising, an enemy is rushing at us, or a highway exit appears just ahead of a traffic jam, we see the looming crisis and respond.
We are not as adept when threats—or threatened resources—are invisible. Some of us have trouble realizing why invisible carbon emissions are changing the chemistry of the atmosphere and warming the planet. Because the surface of the sea is all we see, it’s difficult to understand that we already have taken most of the large fish from the ocean, diminishing a major source of food. Neither of these crises are visible—they are largely out of sight, out of mind—so it’s difficult to get excited and respond. Disappearing groundwater is another out-of-sight crisis.
Groundwater comes from aquifers—spongelike gravel and sand-filled underground reservoirs—and we see this water only when it flows from springs and wells. In the United States we rely on this hidden—and shrinking—water supply to meet half our needs, and as drought shrinks surface water in lakes, rivers, and reservoirs, we rely on groundwater from aquifers even more. Some shallow aquifers recharge from surface water, but deeper aquifers contain ancient water locked in the earth by changes in geology thousands or millions of years ago. These aquifers typically cannot recharge, and once this “fossil” water is gone, it is gone forever—potentially changing how and where we can live and grow food, among other things.
A severe drought in California—now approaching four years long—has depleted snowpacks, rivers, and lakes, and groundwater use has soared to make up the shortfall. A new report from Stanford Universitysays that nearly 60 percent of the state’s water needs are now met by groundwater, up from 40 percent in years when normal amounts of rain and snow fall.
Relying on groundwater to make up for shrinking surface water supplies comes at a rising price, and this hidden water found in California’s Central Valley aquifers is the focus of what amounts to a new gold rush. Well-drillers are working overtime, and as Brian Clark Howard reported here last week, farmers and homeowners short of water now must wait in line more than a year for their new wells.
In most years, aquifers recharge as rainfall and streamflow seep into unpaved ground. But during drought the water table—the depth at which water is found below the surface—drops as water is pumped from the ground faster than it can recharge. As Howard reported, Central Valley wells that used to strike water at 500 feet deep must now be drilled down 1,000 feet or more, at a cost of more than $300,000 for a single well. And as aquifers are depleted, the land also begins to subside, or sink.
Unlike those in other western states, Californians know little about their groundwater supply because well-drilling records are kept secret from public view, and there is no statewide policy limiting groundwater use. State legislators are contemplating a measure that would regulate and limit groundwater use, but even if it passes, compliance plans wouldn’t be required until 2020, and full restrictions wouldn’t kick in until 2040. California property owners now can pump as much water as they want from under the ground they own.
California’s Central Valley isn’t the only place in the U.S. where groundwater supplies are declining. Aquifers in the Colorado River Basin and the southern Great Plains also suffer severe depletion. Studies show that about half the groundwater depletion nationwide is from irrigation. Agriculture is the leading use of water in the U.S. and around the world, and globally irrigated farming takes more than 60 percent of the available freshwater.
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photo one and two by PETER ESSICK
Photo three by GEORGE STEINMETZ