Ground collapses across Arizona’s Willcox Basin as decades of groundwater pumping take their toll

The Willcox Basin in southeastern Arizona, about 120 km (75 miles) east of Tucson, is collapsing under decades of intensive groundwater use. Once a thriving agricultural valley, it now bears visible scars of overpumping: fissures tearing across roads, wells running dry, and unexpected pools forming after rainstorms where the ground has caved.

These new flood pockets appear where the land surface has sagged unevenly. When storms sweep across the high desert, water now collects in shallow depressions created by subsidence, turning farmland into temporary lakes.

For years, local farms drew groundwater freely, with no regional limits or oversight. “For a long time, there were no water regulations there,” said Dr. Danielle Smilovsky, a geospatial research scientist at the Conrad Blucher Institute.

Smilovsky presented new findings at GSA Connects 2025 in San Antonio, Texas. Her five-year study of the Willcox Basin from 2017 to 2021 used satellite radar to measure land motion with millimetre precision. She found that some areas were sinking as fast as 15 cm (6 inches) per year and that the ground has dropped nearly 3.5 m (12 feet) since the 1950s, the fastest rate in Arizona.

The invisible collapse beneath the surface

The sinking land begins underground. As groundwater is extracted, the pressure that supports the sediment layers weakens. Normally, that pore pressure acts like a hydraulic lift, helping hold up the overlying ground. When too much water is withdrawn, the pores collapse.

“Over time, those pore spaces that were once being held open by water pressure start to collapse,” explained Brian Conway, a geophysicist at the Arizona Department of Water Resources. “That causes the surface to sink because of the compaction happening in the subsurface.”

This process, called aquifer compaction, is irreversible. Once the sediment grains compress, the space that once stored water is permanently lost. Even if rain or snow later recharge the aquifer, it can never hold the same volume again.

Across the Willcox Basin, this collapse has destroyed natural storage that once buffered farms and communities during dry years. The result is a long-term loss of both water and resilience, a crisis that cannot be reversed, only slowed.

Tracking a vanishing landscape from orbit

To measure the changes, Smilovsky and her colleagues used Interferometric Synthetic Aperture Radar, or InSAR. The method compares repeated satellite radar scans to detect ground movement with centimetre-level accuracy.

The research team analysed data from the European Space Agency’s Sentinel-1 satellites and the Japan Aerospace Exploration Agency’s ALOS missions. The results revealed two main deformation zones sinking faster than 15 cm (6 inches) per year.

They cross-checked these satellite observations with ground-based GPS data and water-level records. Together, they confirmed that subsidence remains active and, in some places, is still accelerating despite temporary recharge from rainfall.

InSAR has revolutionized the way scientists monitor groundwater systems. It allows researchers to track how aquifers respond to both extraction and recharge without drilling or disturbing the ground. By turning the land surface into a natural sensor, scientists can map exactly where the Earth is giving way.

Rain brings brief relief, but the desert takes it back

During the winter of 2022 to 2023, Arizona’s mountains received heavy snowfall and the basin experienced above-average rain. For a short time, the sinking slowed.

Smilovsky’s team noted small rebounds in groundwater levels, particularly around the Willcox Playa, a flat lakebed where fine-grained sediments temporarily absorbed some of the excess water. But when the following summer turned hot and dry, most of that gain evaporated.

The data showed that the respite was temporary. While parts of the basin briefly stabilized, others continued to subside, and in several zones, the sinking actually accelerated. The brief recharge was not nearly enough to offset a water deficit of more than 123 million cubic metres (100 000 acre-feet) every year.

In arid basins like Willcox, nature cannot refill what decades of pumping have withdrawn. Without management, the land’s slow collapse will continue, deepening the scars already visible from space.

Regulation arrives after decades of decline

Until recently, Willcox was one of Arizona’s largest unregulated groundwater areas. That changed in 2025, when the state government declared it an Active Management Area, or AMA.

Under the AMA framework, groundwater extraction is monitored and capped to balance withdrawals with recharge. The decision followed a failed 2022 local ballot initiative and growing pressure from residents facing fissures and sinking farmland.

Other regions of Arizona provide a model for what could follow. In Phoenix and Tucson, AMAs introduced decades earlier have stabilized water levels and reduced or even halted subsidence. “Especially in the Phoenix and Tucson areas, groundwater levels are recovering, and we’ve seen subsidence rates decrease quite a bit,” said Conway. “In the Tucson area, we’re not even seeing subsidence anymore.”

Still, the changes in Willcox are largely permanent. “It needs to not be a desert,” Smilovsky remarked. “I don’t think subsidence will ever stop, but an AMA might slow it down.”

The new regulations are expected to limit irrigation pumping, encourage recharge projects, and promote water-efficient crops. But any recovery will take decades, and much of the damage cannot be undone.

New satellites watch the desert breathe

In 2025, NASA and the Indian Space Research Organisation launched the NISAR satellite, a new radar mission built to track ground movement across the planet. NISAR carries two radar systems, operating in L- and S-bands, which can detect shifts as small as a few millimetres even through vegetation and dry soils.

The satellite revisits each location roughly every 12 days, providing unprecedented temporal resolution for monitoring how land responds to changes in water storage. The Willcox Basin is one of several test sites expected to validate the mission’s early data.

By combining NISAR with existing Sentinel-1 and ALOS observations, scientists will soon have continuous records of how the basin reacts to both seasonal rains and long-term policy changes. This will allow water managers to see in near real time whether new regulations are slowing the subsidence.

For resource managers, such data turn abstract groundwater policy into something visible and measurable. The land itself becomes the indicator of success or failure.

A warning carved into the desert

The Willcox Basin now serves as both a warning and a case study for arid regions across the world. From California’s Central Valley to Mexico’s Sonoran Basin, the same forces are at work: intensive groundwater extraction, insufficient recharge, and the slow compaction of the subsurface.

But Willcox stands out for its pace and severity. Its surface has dropped by more than 3.5 m (12 ft) in places, leaving cracked fields and tilted structures. The basin’s landscape records a geological transformation in real time, one driven entirely by human water use.

As satellite data continue to reveal the scale of this transformation, the message is unmistakable: once an aquifer collapses, it cannot be rebuilt. The desert’s memory is written in its sinking ground, and its warning is clear, sustainability delayed is stability lost.

References:

¹ The Land Is Sinking Fast in Arizona’s Willcox Basin – GSA – (please add date, cant find it)

Reet Kaur

I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.

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