Western US states using up groundwater at an alarming rate

Eric Hand in Science:  For the past 14 years, drought has afflicted the Colorado River Basin, and one of the most visible signs has been the white bathtub rings around the red rocks of Lake Mead and Lake Powell, the two biggest dammed lakes on the river. But there is also an invisible bathtub being emptied, below ground. A new study shows that ground water in the basin is being depleted six times faster than surface water. The groundwater losses, which take thousands of years to be recharged naturally, point to the unsustainability of exploding population centers and water-intensive agriculture in the basin, which includes most of Arizona and parts of Colorado, California, Nevada, Utah, New Mexico, and Wyoming.

The study is the first to identify groundwater depletion across the entire Colorado River Basin, and it brings attention to a neglected issue, says Leonard Konikow, ahydrogeologist emeritus at the U.S. Geological Survey in Reston, Virginia, who was not involved with the work. Because ground water feeds many of the streams and rivers in the area, Konikow predicts that more of them will run dry. He says water pumping costs will rise as farmers—who are the biggest users of ground water—have to drill deeper and deeper into aquifers. “It’s disconcerting,” Konikow says. “Boy, water managers gotta do something about this, because this can’t go on forever.”

...Famiglietti says it makes sense that cities and farmers turn from surface water to ground water during drought. But he is surprised by the magnitude of the loss. The groundwater depletion rate is twice that in California’s Central Valley, another place famous for heavy groundwater use.

Regulation and monitoring of groundwater extraction are rare. The basin’s surface water is apportioned precisely under the Colorado River Compact, a 1922 agreement among seven states. In contrast, groundwater extraction is often the local right of the landowner. “If you own the property, you can drill a well and pump as much as you want,” Famiglietti says. “That’s just the way it is.”...

The Mark Wilmer Pumping Plant on Lake Havasu, on the border between Arizona and California, near Lake Havasu City, Arizona. Shot by Kjkolb, Wikimedia Commons,  under the Creative Commons Attribution-Share Alike 3.0 Unported license