Groundwater pumping in the last century has contributed as much as 50 percent to stream flow declines in some U.S. rivers, according to new research led by a University of Arizona hydrologist.
The new study has important implications for managing U.S. water resources. Laws regulating the use of groundwater and surface waters differ from state to state. Some Western states, Arizona among them, manage groundwater and surface water separately.
“We’re trying to figure out how that groundwater depletion has actually reshaped our hydrologic landscape,” said first author Laura Condon, a University of Arizona assistant professor of hydrology and atmospheric sciences. “What does that mean for us, and what are the lasting impacts?”
Condon said this is the first study to look at the impact of past groundwater pumping across the entire U.S. Other researchers have examined how groundwater pumping affected surface waters, but at smaller scales.
Using a computer model, Condon and her co-author, Reed Maxwell of the Colorado School of Mines in Golden, determined what U.S. surface waters would have been like without significant consumptive uses and compared that with surface water changes since large-scale groundwater pumping began in the 1950s.
The scientists focused particularly on the Colorado and Mississippi River basins and looked exclusively at the effects of past groundwater pumping because those losses have already occurred.