29 July 2014
Rainfall in Pittsburgh is normal this year but out West they’re in their 14th year of drought with no end in sight. This is starkly obvious at Lake Mead near Las Vegas where the water level has dropped 138 feet, leaving a “bathtub ring” of mineral deposits.
Seven western states and Mexico depend on Lake Mead for water; three states depend on its dam for electricity. Since last October 4.2 million acre feet came into the lake but 7.9 million was withdrawn. The lake has dropped 30 feet in the past five months alone. As the water drops so does Hoover Dam’s generating capacity, putting the electric supply at risk too.
You’d think this problem could be fixed by controlling surface water consumption but it goes much deeper than that.
Back in January, I wrote about NASA’s GRACE satellite pair that measures groundwater from outer space (click here to read how it works). Using nine years of GRACE data from the Colorado River Basin, University of California Irvine and NASA scientists made an alarming discovery. From December 2004 to November 2013 the watershed lost 53 million acre-feet of water, an amount almost twice the size of Lake Mead. More than 75% of that loss was from groundwater. No one knows how much water is underground but it’s going fast.
When wells deplete groundwater, there are significant downstream consequences. A 2012 study by Stanford Woods Institute found that overpumping can make the surface run dry. Though surface water is carefully managed in the West, groundwater use is often poorly documented and barely managed — if at all.
Water loss at this scale affects every living thing. Near Las Vegas the wetlands along Lake Mead are gone and so are the birds and animals that depended on them.
If the loss continues at this rate, humans may have to leave Las Vegas, too.
(photo of Lake Mead by U.S. Bureau of Reclamation)