A new study by the United States Geological Survey finds vigorous pumping of aquifers during a drought can expedite the deterioration process of groundwater.
This study coupled over 160,000 measurements of nitrate from ∼6,000 public-supply wells with a 30-year reconstruction of groundwater levels throughout California's Central Valley to evaluate dynamic relations between aquifer exploitation and resource quality, Agupubs reported.
Researchers examined 30 years of data from the Central Valley to find increasing nitrate concentrations at public drinking-water wells were more prevalent in areas where groundwater levels dropped rapidly during drought, Agupubs reported. Nitrate is a contaminant from fertilizer typically present at elevated concentrations in shallow groundwater throughout the Central Valley due to decades of agricultural land use. Scientists found that increased pumping from wells during drought can pull shallow, contaminated groundwater down to depths commonly tapped for public drinking-water supply.
“Water quality problems from legacy groundwater pollution could get worse, faster, when pumping increases during drought,” Dr. Zeno Levy, a research geologist with the USGS said in a USGS press release. “This could lead to more public drinking-water wells being shut down if costly treatment or cleaner water sources to mix with are not available."
The USGS reports that previous groundwater research has focused on the risk of wells being overdrawn and running dry during the drought. The new study showcases advancements to understanding the related consequences to water quality caused by over-pumping.
"Groundwater provides approximately (one-third) of fresh water used by humans on the planet, but can be vulnerable to depletion during drought—particularly in large, regional aquifers that support irrigated agriculture," the Agupubs report stated.
The study was part of a collaborative effort of the USGS and the California State Water Resources Control Board’s Groundwater Ambient Monitoring and Assessment Program.
