Groundwater pumping is causing rivers and small streams throughout the country to decline, according to a new study from researchers at the Colorado School of Mines and the University of Arizona.
Scientists have known for a while that there’s a link between groundwater and surface water that runs through streams and rivers. Previous studies have shown pumping near a stream will eventually cause its levels to drop.
“If you pump near a stream you’re going to change the amount of water that flows through the stream, because some of that stream water is going to basically get pulled to the well instead of flowing down the stream,” said Reed Maxwell, hydrologist at Colorado School of Mines and the study’s co-author.
Maxwell says his new study with hydrologist Laura Condon at the University of Arizona goes broad, quantifying the effect of pumping across the country.
“What we found is that we have actually depleted streams quite a bit,” Maxwell said.
The study finds that since the 1950s, groundwater pumping has caused some stream flows to decline upwards of 50%. Some streams have disappeared from the surface altogether, seeping underground to refill pumped groundwater, the study finds.
Declines are particularly stark in portions of the Colorado River basin and on the Great Plains, Maxwell said.
Using a computer model, researchers were able to envision what rivers across the U.S. would’ve looked like without widespread groundwater pumping, which took hold in the 1950s.
The U.S. Geological Survey has put the loss of groundwater over the 20th century at 649 million acre-feet. One acre-foot is enough water to supply roughly two households’ water use for a year.
“There’s nothing inherently wrong with groundwater pumping,” Maxwell said. “What we want to do is understand what is a long term sustainable amount of pumping. And particularly groundwater because it’s a buffer between wet and dry years.”
Condon and Maxwell’s article is published in the journal Science Advances.
This story is part of a project covering the Colorado River, produced by KUNC and supported through a Walton Family Foundation grant. KUNC is solely responsible for its editorial content.