For the past 20 years, two small satellites orbiting 250 miles above Earth have tracked a stark reality about the nation’s groundwater supplies, including across the parched Colorado River Basin: The water underground is vanishing.
The NASA satellites began gathering data in 2002. Since then, Colorado River Basin groundwater has depleted much faster than water storage in the nation’s two largest reservoirs, according to research that underscores concerns about the increasingly tight water supply in the drought-stricken West.
“We pay a tremendous amount of attention to the disappearance of surface water because we can see what’s happening with the reservoirs, Lake Powell and Mead,” hydrologist Jay Famiglietti said. Meanwhile, he warned, “groundwater is quietly disappearing.”
Famiglietti, a professor of hydrology and executive director of the Global Institute for Water Security at the University of Saskatchewan, presented research based on the satellite data at last week’s fifth annual CSU Spur Water in the West Symposium held in Denver. Famiglietti highlighted data that showed groundwater depleting at six and a half times the rate of water storage in Lake Powell and Lake Mead between 2002 and 2014. “The results are still pretty much the same,” Famiglietti said.
Spearheaded by NASA’s Jet Propulsion Laboratory at the California Institute of Technology, the water-tracking satellite mission is formally known as the Gravity Recovery and Climate Experiment. The GRACE satellites can effectively measure water mass from space by observing gravitational changes, Famiglietti said.
When there’s more water mass on the ground, say, from a storm that just dumped a bunch of snow on the Rockies, that region exerts a greater gravitational tug on the satellites, pulling the instruments down a few centimeters, Famiglietti said. Conversely, he said, if there’s less water on the ground a region will exert less pull on the satellites, which then float a teeny bit higher in orbit.
“It’s like a scale that moves up and down with the weight of water on the ground,” he said. “And so it allows us to map out regions around the world that are gaining or losing water mass on a monthly basis.”
The first GRACE mission launched in 2002. The original two satellites were only forecasted to last about five years, but kept running for about 15. NASA authorized a second mission, and two new satellites went into orbit in 2018. Famiglietti hopes the research will continue for decades. The timing of the GRACE data coincides with what scientists believe is the driest 22-year stretch across the southwestern U.S in the past 1,200 years.
In his talk, Famiglietti urged more consideration of groundwater depletion in discussions over the future of the Colorado River. He also explained that this is a challenge globally. Famiglietti has mapped plummeting groundwater levels — he said the drops are owed mostly to food production — happening everywhere from California’s central valley and the midwestern Ogallala Aquifer to parts of India, northern Africa and the Arabian Peninsula.
Because much of this groundwater ends up flowing into the ocean, he said, it’s compounding the problem of rising seas.
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“The groundwater contribution to sea level rise is about as big as the ice sheets, which is new and something for us to pay particular attention to because it’s one of the few things that we can actually manage,” Famiglietti said.
At some point, pulling water out of the ground will become out of reach, Famiglietti said. “What happens as you go deeper and deeper is the quality generally degrades. You have to dig deeper wells, which gets more and more expensive,” he said. “It gets to the point where even if the water is there it becomes brackish and brine.”
The warning comes at a time in which some Colorado communities already look deep underground for water. In the aquifers that make up the Denver Basin, wells must go thousands of feet deep to access water. That’s led some communities to consider elaborate, pricey plans to get water from other parts of the state.
This summer, for example, the Douglas County Commissioners considered a controversial proposal from Renewable Water Resources, a group backed by former Gov. Bill Owens, to bring in water from the San Luis Valley. Water users in the valley, however, also rely in part on an aquifer for water, and have their own sustainability challenges.
The commissioners voted earlier this year against using money from the American Rescue Plan Act to fund the RWR project. Another proposal, this one led by Parker’s water department, would bring water from the South Platte River to Douglas County via 125 miles of pipeline. Parker purchased agricultural land and water rights near Sterling with the intention of transporting the water to their fast-growing community.
Still, many Colorado communities rely more on surface water than groundwater, said John Tracy, director of Colorado State University’s Colorado Water Center. For that reason, he said that the statewide conversation tends to focus on surface water requirements such as interstate compacts.
“Colorado proportionally uses much less groundwater than surface water — everything comes down to the surface compacts,” Tracy said. “Even in the San Luis Valley much of it is focused on groundwater as it relates to the Rio Grande Compact.”
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One of the keys to addressing disappearing groundwater, Famiglietti said, is to involve the industries that use the water. “It’s time for some corporate water leadership,” he said.
In particular, Famiglietti pointed to the agriculture industry, a significant water user. In Colorado, ag accounts for about 85% of water use statewide. “The challenge there is going to be making sure farmers have the incentives and support,” Famiglietti said.
Nevertheless, despite the challenges, and what he described as the slow burn of reviewing this alarming data for two decades, Famiglietti said he sees cause for optimism — if only because there are few choices left but to do something.
“I’ve kind of flipped from being a pessimist,” he said. “We’re going to do something because we’re at the end of the road.”