California’s San Joaquin Valley Is Sinking At An Alarming Rate

Posted: Mar 6 2017, 12:46pm CST | by , Updated: Mar 6 2017, 12:55pm CST, in News | Latest Science News

California’s San Joaquin Valley is Sinking at an Alarming Rate
Relative expansion of the subsidence bowl in the east of California Aqueduct between March 2015 (left) and June 2016 (right). Credit: NASA/JPL-Caltech/ESRI

NASA research shows decline in underground water levels due to overpumping over the years

California’s San Joaquin Valley is sinking at an alarming rate because of excessive pumping of groundwater, a new NASA study suggests.

Water levels in some parts of the valley have dropped to as much as 28 feet since 1920s, which is sparking serious concerns in water managers as well as state and federal officials.

San Joaquin Valley of California is one of the most productive agricultural regions in the country and farmers here rely heavily on groundwater for their water supply. Over time, excessive water extraction accompanied by land subsidence has damaged thousands of public and private groundwater wells throughout the San Joaquin Valley and this persistent decline in water levels is now putting the at risk the very system that brings water to the region.

To determine the extent to which groundwater pumping further aggravates land subsidence, researchers from NASA’s Jet Propulsion Laboratory at Pasadena collected and analyzed airborne and satellite radar data from 2015 and 2016. The latest study builds on a previous research to identity the pace and extent of the groundwater depletion in San Joaquin Valley. Researchers used radar data from several different sensors between 2006 and early 2015 effort.

Several trouble spots identified in the first report that are continue to sink almost 2 feet per year. Two main subsidence bowls are found near the towns of Chowchilla and Corcoran. These bowls are already covering hundreds of square miles and are getting wider and deeper over time. Small land subsidence bowls were also identified in the Sacramento Valley near Davis and Arbuckle.

“If you see a subsidence bowl, then something is going on at the center of the bowl that is causing the land to sink -- for example, high levels of groundwater pumping,” said JPL report co-author Cathleen Jones. “We can locate problem spots so the state can focus on those areas, saving money and resources. We find the needle in the haystack, so to speak.”

NASA research is focused on California Aqueduct, which is the main system of canals, pipelines and tunnels and supplies water to 25 million Californians and nearly a million acres of farmland. As a result of years-long subsidence and water pumping in this area, the aqueduct is now carrying a reduced flow of only 6,650 cubic feet per second -- 20 percent less than its design capacity of 8,350 cubic feet per second.

In the future, researchers will systematically collect data over California and the world and will track the changes to the land subsidence associated with groundwater pumping, as well as threats associated with future water supplies.

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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