A new study by the U.S. Geological Survey throws cold water on the idea. To be fair, the study doesn't say that the Spring Valley scheme would be a disaster. There may be a safe amount of ground water that can be withdrawn from beneath the valley every year without severely damaging other water users, wildlife and plants in Nevada or Utah.
But what the study does suggest is that no one knows exactly what that safe amount is.
To begin with, the geology and hydrology beneath the valleys of the Great Basin are complex. What this latest study argued is that the aquifers beneath Spring, Snake and Steptoe valleys (there are a dozen valleys in the system) are closely linked, and that ground water flows from one valley to another in larger quantities than previously estimated.
What that means is that if you withdraw ground water from Spring Valley, it is more likely than previously thought to affect springs, seeps and wells in Snake Valley.
On the face of it, there is ground water available to send to Vegas, because the regional system as a whole discharges 90,000 acre-feet of ground water a year less than the total new water that Mother Nature puts into the aquifers. Some of that discharged water flows toward the Great Salt Lake, some toward the Colorado River.
But a closer look shows that the aquifers are in equilibrium. Withdraw large gulps of water for Las Vegas and supplies will suffer.
That's one reason why the Nevada state engineer, who governs water rights, urged caution. He ruled that the Southern Nevada Water Authority may take 40,000 acre-feet a year from Spring Valley for 10 years, but the hydrology must be closely monitored. If existing water rights are impacted, or the pumping is found to be environmentally unsound, Las Vegas will be ordered to curtail pumping or mitigate the loss.
Nevada has the right to decide what to do with its water. But Utah has a dog in this fight, and Utah officials must vigorously protect Utahns' water in Snake Valley during negotiations with Nevada. The USGS study clearly shows why.
