Recent satellite data indicates that the Colorado River basin has experienced significant groundwater loss over the past few decades, raising concerns that this vital resource could be depleted by the century’s end.
But how accurate is this claim? If it’s valid, what measures can we take to avert this crisis?
Although groundwater depletion is a serious issue, experts told Live Science that a complete disappearance of this water source is improbable. However, the continuous drainage from the basin could significantly lower water tables.
A Vast Basin
The Colorado River flows through seven U.S. states (Wyoming, Colorado, Utah, New Mexico, Nevada, Arizona, and California) and two states in Mexico (Baja California and Sonora). Approximately 40 million individuals depend on its water resources, including residents of Phoenix and Las Vegas. Nevertheless, this surface water supply has dwindled over the last two decades, with reports indicating that it has reached record lows. Groundwater has been extensively extracted from underground sources, predominantly for agriculture.
For a clearer picture of groundwater extraction, Jay Famiglietti, the Director of Science at Arizona State University’s Arizona Water Innovation Initiative, along with his team, has utilized data from NASA’s Gravity Recovery and Climate Experiment (GRACE) and its Follow-On missions. These satellites monitor fluctuations in Earth’s gravitational field, enabling scientists to gauge shifts in groundwater levels in conjunction with data on snowmelt, surface water, and soil moisture.
Researchers estimate that pumping from wells since 2003 has removed around 28 million acre-feet (approximately 34 cubic kilometers) of groundwater from the Colorado River basin, equivalent to the capacity of Lake Mead, the largest reservoir in the U.S., situated behind Hoover Dam on the Colorado River. This study was published in the journal on May 27th, in Geophysical Research Letters.
Findings reveal that about 25% of groundwater depletion occurs in the lower stretches of the river, predominantly in Arizona, where water is extracted from desert aquifers for irrigation. Many farms in these rural areas lack connection to municipal water systems and rely instead on water pumped from site-specific wells. Due to the privatization of these wells, local, county, or state authorities often lack precise measurements of water usage.
Famiglietti and his team estimate that the average annual groundwater losses in the basin exceed 1.2 million acre-feet (1.5 cubic kilometers), and if this trend continues, it could lead to severe water shortages and hinder agricultural productivity.
“We’re at a critical juncture, delving deeper into the aquifers and experiencing declines in water quality,” Famiglietti asserted.
Numerous wells have run dry in the region. Land subsidence caused by a collapsing aquifer and Fissures have developed.
Risks of Severe Depletion
Ryan Mitchell, chief hydrologist at the Arizona Department of Water Resources and not involved in the recent study, expressed concern regarding the groundwater depletion levels cited in some areas. Nevertheless, he raised objections to claims stating that the Arizona Department of Water Resources’ simulations demonstrated complete depletion of groundwater by the century’s end, stating that these simulations indicated no total depletion of groundwater, let alone within this timeframe.
He clarified that while groundwater may not be entirely depleted, the data from GRACE satellites and water use can’t accurately indicate remaining water quantities in the aquifers.
“It’s akin to asking how many grains of sand exist on a beach. You can hypothesize and estimate, but you cannot determine the exact total,” Mitchell explained.
Bridget Scanlon, a research professor at the University of Texas at Austin, and her team recently investigated similar issues using GRACE data. They identified a comparable trend and noted that groundwater consumption surged as irrigation expanded from the 1940s to the 1970s, before experiencing a recovery period during the rainy seasons of the early 1980s and 1990s.
Related: Atlantic currents are weakening, potentially altering climate patterns in various regions.
However, the landscape has shifted significantly since then based on local management practices. In “Active Management Areas,” where water usage is regulated, groundwater levels have generally remained stable. While water extraction occurs, managerial practices enable the redirection of surplus water back into aquifers in depleted regions.
In mismanaged areas, however, no oversight exists to track groundwater extraction, leading to decreased awareness on when aquifers should be replenished. Mitchell emphasized to LiveScience that unchecked extraction in these uncontrolled areas exacerbates groundwater depletion.
“Without measurement, we cannot exert control,” he said. “This highlights that having regulations, monitoring water usage, and proactive management can sustain resource levels.
One thing remains certain: relying solely on precipitation to replenish aquifers is insufficient. Research indicates that Colorado River flow is predicted to continue declining due to climate-associated reductions in snow and rainfall. This translates to less surface water available, diminished aquifer recharge, and increased demand for groundwater extraction.
Drilling deep wells is one possible solution, though it presents challenges, Famiglietti noted. The costs can reach millions for deep wells, which also entail higher energy expenses for pumping and potential treatment requirements.
“As you tap deeper into groundwater, it has been in contact with soil and rock for extended periods, leading to the dissolution of salts and solids,” Famiglietti explained. This can result in water that is salty or potentially contain high arsenic levels. “Furthermore, since agricultural runoff often contaminates these water sources, they can accumulate elevated levels of pesticides and fertilizers,” Famiglietti added.
Another strategy involves minimizing water usage by shifting away from water-intensive crops like alfalfa. Famiglietti emphasized, “Business as usual is no longer viable. We must prioritize water conservation.”
“My concerns for tomorrow are as pressing as those for a century from now. It’s evidently clear that improved groundwater management is essential, particularly in Arizona’s lower regions,” he remarked. “Currently, only 18% of the area is actively managed, while significant depletion is ongoing in unmanaged regions.”
Experts from Live Science contend that expanding active water management areas can provide solutions. Ultimately, this involves tracking usage and replenishing water extraction.
Such a strategy could include importing water from distant sources, as evidenced by San Antonio’s purchase and transport of water from East Texas over 150 miles (240 km).
“Groundwater is a limited resource,” Mitchell remarked. “We need to ensure its natural recharge and find a way to replenish what we are utilizing. Based on Scanlon’s research findings, “We can maintain stable conditions in managed zones but face challenges elsewhere.”
Legislative efforts are underway in Arizona to broaden areas of active management, though similar initiatives have faced resistance. Opponents argue that such restrictions could threaten existing agricultural water use and hinder economic expansion, while others prefer local water districts governed by elected representatives.
“We’re not monitoring anyone; we simply wish to understand our water resources,” Mitchell stated. “However, public trust in government is historically low. We aim to establish frameworks that aid families in saving water resources, especially since [600 meters] wells are increasingly deep and costly. We seek to assist them in safeguarding their water supplies.”
Editor’s Note: This article was updated at 9 am ET on June 16th, correcting a quote attributed to Bridget Scanlon on behalf of Ryan Mitchell.
Source: www.livescience.com