Groundwater in the Colorado River Basin is low, raising farmers’ electric bills
Groundwater in Arizona and the rest of the Colorado River Basin is drying up fast, and it’s causing farmers to spend more money in attempts to reach diminishing water supplies under the earth’s surface.
A study from Arizona State University published in May found that the Colorado River Basin, which stretches across parts of Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming, has lost enough water over the past 10 years to fill Lake Mead. The water loss is most pronounced in Arizona, where many farmers are reliant on pumping groundwater to the surface.
“Groundwater is being used faster than expected in the whole Colorado River Basin,” said Karem Abdelmohsen, a post-doctoral researcher at Arizona State University and first author on the study, in an interview with Straight Arrow News. “As groundwater levels drop, it becomes more expensive to access water.”
What is causing Arizona groundwater to drop?
The study, published in Geophysical Research Letters, analyzed satellite data from NASA’s Gravity Recovery and Climate Experiment (GRACE). The GRACE data measures the amount of water above and below the earth’s surface by tracking changes in the earth’s gravity. Researchers combined this information with additional climate data to estimate groundwater levels.
Researchers found that the rate of groundwater loss between 2015 and 2024 was three times faster than it was between 2002 and 2014. Abdelmoshen and his colleagues found that 74% of that water loss occurred in the lower basin, which includes the area around Las Vegas, part of Southern California and nearly all of Arizona. The region has lost an estimated 25.5 cubic kilometers of groundwater over 20 years – enough to meet the current water consumption of the entire city of Los Angeles for 46 years, according to an analysis by Straight Arrow News.
“A majority of those losses are related to agriculture water use,” Abdelmoshen said. The ongoing drought has decreased surface water flows, forcing farmers to become more reliant on groundwater. He added that farmers in some regions of Arizona are entirely dependent on groundwater.
Less groundwater makes farming more expensive
In the Colorado River Basin, farmers’ electricity costs over the past decade have increased faster than the United States average, according to data from the U.S. Department of Agriculture’s Irrigation and Water Management Survey, which is published every five years and was last released in 2023.
As more water is extracted from aquifers under the earth’s surface, the water table – the depth underground at which water can be reached – also gets lower. “More energy is taken to pump the deeper the water is,” said Sharon Megdal, director of the University of Arizona Water Resources Research Center, in an interview with Straight Arrow News.
In Arizona, the yearly electricity costs per acre to pump water from aquifers to farms on the surface increased 28.7% between 2018 and 2023, compared to 16.7% nationwide. California saw a 44.5% increase over the same period, due largely to dwindling groundwater in the state’s Central Valley region, which is not part of the Colorado River Basin. Farmers in Arizona and California spend $147 and $208 per acre to pump groundwater, according to USDA data.
Megdal said the Arizona data can be explained by “a mix of circumstances.” In 2021, the federal government declared a water shortage on the Colorado River and cut Arizona’s allocation of surface water by 18%. Not only did that make farmers in Central Arizona more dependent on pumping groundwater, but it also reduced the “incidental recharge” of aquifers that would occur when a portion of surface water applied to crops sinks into the earth and becomes groundwater.
Megdal acknowledged that changes in the price of electricity could also play a role, but “as the reliance [on groundwater] has increased in Central Arizona,” she said, “over time, you would expect that the pumping cost per acre-foot of water is going to go up.”
Criticism of the study
The Arizona Department of Water Resources has raised concerns about certain aspects of the study, including a sentence that suggested groundwater could be depleted by the end of the century, as well as the reliance on satellite data to estimate the remaining water supply.
“It’s almost like it’s an unknowable number in the same way that if someone said how many grains of sand are on the beach, you could make some assumptions and make some guesses, but you can never actually know the exact amount of sand grains,” said Ryan Mitchell, the department’s chief hydrologist, in an article for Live Science.
How is Arizona groundwater regulated?
The Arizona Department of Water Resources did not respond to questions from Straight Arrow News. In recent years, the state has been making changes to its groundwater management.
Starting in the 1980s, the state established “active management areas,” known as AMAs, where groundwater use would be regulated with the goal of reducing consumption. The area included in the initial AMAs was limited to mostly Central Arizona. Still, in recent years, voters have agreed to create one new AMA in the southeast region of the state, and Gov. Katie Hobbs has ordered another be created where voters rejected the measure. The agriculture industry in the proposed Willcox Valley AMA fought against the ballot measure, saying it would stifle farms and the growing wine industry there.
Arizona has implemented strict water planning requirements for new development through its Assured and Adequate Water Supply programs. Before construction can begin, developers must submit documents demonstrating that enough water resources are available to guarantee a 100-year water supply.
But most land in the state is not subject to groundwater management, Abdelmohsen said, adding that expanding state-level management is “critical” to “preserve water resources for future generations.”
“To make progress is a real challenge because you’ve got a lot of vested interests,” said Bill Alley, director of science for the National Groundwater Association. Fast-growing residential areas, new industries such as semiconductor manufacturing and the state’s agriculture sector each need ample amounts of water.
Megdal hopes that all those interests can find a way to work together. “It’s in everybody’s interest to manage better groundwater in areas where it’s being overdrafted, sometimes at rapid rates,” she said. “Agriculture wants to survive over the long term, and that water’s in limited supply.”
Ella Rae Greene, Editor In Chief
