Groundwater supply in a warming climate

Posted at 10:34 AM, Jul 12, 2021

TUCSON, Ariz. — The Colorado River is a lifeline for water in the southwest, but the importance of groundwater here and across the country shouldn't be overlooked.

“It’s actually our largest unfrozen freshwater resource, it’s much larger than our rivers and streams,” said University of Arizona Department of Hydrology and Atmospheric Sciences Assistant Professor Laura Condon.

A UArizona study published in February 2020 showed a modest climate warming of just a couple of degrees would lead to the loss of millions of cubic meters of groundwater in the United States. Roughly four times the water in Lake Powell.

RELATED: Maps show stark picture of drought levels across western U.S.

“We transported ourselves to a warmer future and watched what happens over 4 years,” said Condon.

Condon says the study showed our desert climate expanding east. Groundwater could only keep the east coast green for a short time.

"So as things are warming and become more arid shallow groundwater can buffer the rate at which that happens,” she said. “But then when the groundwater is used up, it's gone, unless we recharge it.”

The Western United States saw less drastic results thanks to desert-adapted plants and deeper reserves of groundwater. But Condon says even here, the groundwater supply is not indefinite. Tucson Water Spokesperson James MacAdam agrees more conservation will be needed for the long term.

"The issue is more about conserving water to prepare for the future, and to make us a more resilient community in the face of what will be an intermittent supply from the Colorado River,” he said.

MacAdam says the Tucson area has a couple decades worth of groundwater available despite several wells being shutdown over pollution concerns. For the utility the water supply over the next 30, 50 or 100 years is a question of logistics.

"As there is less Colorado River Water it will become more expensive, and the more PFAS contamination spreads the more expensive it will be to clean it up,” said MacAdam.

For Condon, it is simply a question of supply and demand.

“We can’t use more than we have coming in, and have that be sustainable,” she said.