Researchers map wells across the West and estimate 1 out of every 30 has gone dry
During California’s severe five-year drought, groundwater levels fell to record lows and people in farming communities from Tulare County to Paso Robles saw their wells go dry.
Now researchers have analyzed records for about 2 million wells across 17 western states from Texas to Oregon, and they estimate that one out of every 30 wells was dry between 2013 and 2015.
The researchers also found dry wells were concentrated in farming areas such as California’s Central Valley and the High Plains. In some areas, they estimated that up to one-fifth of wells were dry.
“Rural communities often bear the brunt of the impacts of declining groundwater levels, because they have limited ability to diversify their economies, and constructing new wells can be costly,” said Debra Perrone, a postdoctoral scholar at Stanford University’s Water in the West program.
Perrone and fellow researcher Scott Jasechko, an assistant professor of geography at the University of Calgary, analyzed records of the construction of wells between 1950 and 2015, and they compared the depth of each well to the local groundwater levels.
Some of the wells were much shallower than the groundwater levels between 2013 and 2015, indicating those wells likely went dry years earlier.
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The study was published Thursday in the journal Environmental Research Letters. The researchers said their analysis provides the first “continental-scale” study of wells in nearly three decades.
Kurt Schwabe, a professor of environmental economics and policy at the University of California, Riverside, said the dataset and the analysis are impressive and helpful.
“The results are very important for a number of reasons, one being to better recognize and identify the potential vulnerabilities small community systems confront prior to the onset of a drought,” said Schwabe, who wasn’t involved in the research.
The scientists limited their study to flatter areas where groundwater levels tend to be relatively uniform, and excluded mountainous areas where aquifer levels may vary more widely.
They used groundwater data from multiple sources to estimate the water table in each area and compared those water levels to the depths of the wells listed in the construction records.
Of the 3.7 million well construction records the researchers collected, about 2.3 million included depth data. The researchers excluded records for some wells that they found were too far away from any of the available groundwater level measurements.
Perrone said the finding that about one-in-30 wells were dry from 2013-2015 is a conservative estimate. It may be an underestimate, she said, because they based their analysis on the bottom of each well rather than the depth of the pump, which is typically somewhat higher up in the well.
In California, well construction information has long been collected at a local level. The state’s Department of Water Resources has been collecting those records and putting them into a statewide database.
Well records were unavailable for portions of the Central Valley as of this summer, when the researchers completed their study.
Information is collected differently in each state, making it difficult to integrate data from multiple states, Perrone said in an email. She said that results in a “patchwork of information” for some aquifers.
“In many cases, it is not that we need more information about groundwater wells,” Perrone said. “It is that we need the information to be collected and presented in a consistent and reliable manner across jurisdictional boundaries.”
Perrone and Jasechko collected information on household wells, farm wells and other wells.
In parts of the Central Valley, relatively shallow household wells have gone dry while farmers have drilled deeper wells to reach the receding water table hundreds of feet underground.
Perrone said the study confirmed that domestic wells are shallower and more susceptible to going dry than agricultural wells in parts of the Central Valley, though not all of it. Outside of California, she said, the depths of household wells and agricultural wells were similar in most of the areas they analyzed.
“In areas where water levels are declining, it is important to understand which kinds of groundwater wells are most at risk,” Perrone said. “This information informs how we go beyond status quo management and move towards sustainable groundwater management.”
Heavy pumping of groundwater has led to declining aquifers in California and across the West.
In an effort to get a grip on the problem, California lawmakers in 2014 passed the Sustainable Groundwater Management Act. Under the law, the 21 groundwater basins with the most severe overdraft problems have until 2020 to adopt 20-year plans for achieving sustainable management — defined as managing aquifers in ways that avoid chronic declines or saltwater intrusion.
California’s five-year drought between 2012 and 2016 was the most severe in modern history. Scientists say climate change is leading to longer and more intense droughts, making groundwater management efforts all the more crucial ahead of the next dry spell.
Ian James writes about water and environmental issues for The Desert Sun. Reach him at ian.james@desertsun.com, 760-778-4693 or on Twitter at @TDSIanJames.
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