From The Grand Junction Daily Sentinel (Gary Harmon):
While water levels at lakes Mead and Powell have visibly slipped in the current drought, another source, groundwater, is disappearing even more rapidly, according to a satellite study of the Colorado River Basin.
A University of California, Irvine, study posted on the website of the American Geophysical Union said that the three-quarters of the water lost in the basin was drawn from groundwater and noted that the extent of groundwater loss “may pose a greater threat to the water supply of the western United States than previously thought.”
But for some water produced far below the surface in drilling for natural gas and oil, there is no groundwater production on the West Slope, said Jim Pokrandt, who chairs the Colorado River Basin Roundtable.
Other water production from the ground taps return flows making their way to creeks and rivers, Pokrandt said.
What is at issue in the loss of groundwater is the unregulated tapping of groundwater in California, said Chris Treese, spokesman for the Colorado River Water Conservation District.
California groundwater “is completely unregulated,” Treese said. “So when drought hits, they turn on the pumps.”
Researchers said they were surprised by the extent to which groundwater appeared to be affected.
“We don’t know exactly how much groundwater we have left, so we don’t know when we’re going to run out,” said Stephanie Castle, lead author of the study. “This is a lot of water to lose. We thought that the picture could be pretty bad, but this was shocking.”
The Colorado River, which serves some 40 million people, supplies water to the Colorado Front Range, as well as the populous cities of California, Arizona and Nevada.
Those lower basin states appear to be on their own, for the moment, said Larry Clever, general manager of the Ute Water Conservancy District.
The upper basin of the Colorado is ahead of its requirement to deliver 75 million acre feet of water to the lower basin over 10 years, “so I don’t think they can come back on us” for more water, Clever said.
That doesn’t mean, however, that there is water in the river to be diverted to the Front Range, Clever said.
“The key issue in this thing is that Powell is going down and there is no water to send to the East Slope.”
Lake Powell’s levels are low enough that water managers are concerned that the lake might be unable to generate electricity, a significant factor in deciding how the river will be managed.
The research was led by NASA and University of California, Irvine, scientists, who used satellite data to gauge changes in the mass of the Colorado River Basin that are related to changes in water on and below the surface.
In the period from December 2004 to November 2013, the basin lost nearly 53 million acre feet of fresh water.
About 41 million acre feet of the loss came from groundwater.
More Colorado River Basin coverage here.