As the ongoing drought casts a sense of urgency on diminishing water supplies in the western United States, researchers have developed innovative ways to measure the scope of the problem. This summer, two studies utilizing advanced technology measured the scope of water depletion across the region.
The first study, written by a team from UC Irvine, NASA, and NCAR, used data from NASA’s GRACE mission. GRACE measures fluctuations in the Earth’s gravity field by tracking variations in the orbits of two identical satellites. From these data, researchers were able to measure the amount of water lost in the Colorado River Basin between 2004 and 2013. In all, the region lost 64.8 cubic kilometers (km3) of freshwater—almost enough to fill Lake Mead twice. Groundwater made up 77% (50.1 km3) of the lost water. The period of fastest decline came in 2013, after the start of the current drought period. The authors argue that these findings underscore the importance groundwater and the need to regulate it more comprehensively.
In August, a study in the journal Science from a team at the Scripps Institution of Oceanography estimated the amount of water lost in the western US (west of 109º W longitude) since 2013. Researchers used data from the network of GPS sensors designed primarily for earthquake detection to measure the uplift, or elevation gain, of the Earth’s crust in the area. The current drought and corresponding decrease in the amount of surface and groundwater in the area has lightened the crust enough that parts of California have seen uplift as large as 50 mm. This equates to a loss of 63 trillion gallons since the beginning of last year. The Scripps study helps fill in some of the gaps left by the GRACE study, most notably by focusing on the 2013-2014 time period, which was not covered in the GRACE data.
With these studies, policymakers now have a clearer picture than ever of the scope of water depletion in the western U.S. What they will elect to do going forward remains to be seen.
Written by Stratecon Staff