A new satellite-based map of Earth’s freshwater has identified the southern High Plains as one of the sharpest groundwater loss zones on the planet, spanning the overlapping territory of Colorado, Kansas, New Mexico, Oklahoma and Texas. The analysis, built from more than two decades of satellite gravity data and published in the Proceedings of the National Academy of Sciences, found that groundwater depletion beneath those five states and other irrigation-heavy regions worldwide is considerably worse than earlier estimates suggested.
Mary Michael O’Neill of NASA’s Goddard Space Flight Center and the University of Maryland led the study alongside NASA co-authors Matthew Rodell and Bryant Loomis, refining satellite measurements down to a finer regional scale than earlier global water maps allowed. The underlying data comes from twin-spacecraft satellite missions that track tiny changes in Earth’s gravity field to measure how much water mass is gained or lost across a given stretch of land, and the team drew on records stretching from April 2002 through November 2025.
A 23-year window is long enough to separate a genuine multi-year drawdown from ordinary seasonal swings between wet and dry years, which is part of why the study’s authors describe their regional trend estimates as a meaningful upgrade over earlier, coarser satellite analyses rather than just a longer dataset covering the same ground. The satellite program itself, NASA’s GRACE and GRACE-FO missions, has been the workhorse behind most global groundwater research for two decades.
Ninety-Four Hotspots, Mapped at Higher Resolution
The team’s method identified 94 distinct regions worldwide where terrestrial water storage shifted by an amount too large to be background noise. Of those, 40 showed a clear statistical link to human activity such as irrigation, dam construction or reservoir management, rather than natural climate variability alone, according to the study’s main text, hosted by NASA’s technical reports server.
The human-driven regions split unevenly. Twenty-two of the 94 hotspots gained freshwater, largely through rain-fed agriculture expansion, new reservoirs and, in some cases, deforestation that altered runoff patterns. The other 18 lost water outright, driven mainly by groundwater-fed irrigation and canal or diversion projects that pull water out of aquifers faster than rain and snowmelt can put it back.
Why the Southern High Plains Stands Out
The five-state stretch of the southern High Plains sits squarely in the loss category. More than 80 percent of irrigated cropland there depends on groundwater rather than surface water or rainfall, according to the NASA-hosted manuscript, which put the region’s water loss at roughly 5.9 gigatons a year. That reliance on a single, slowly refilling aquifer system is exactly the setup the study’s refined satellite method was designed to catch.
“It has become very dire in a lot of places,” said Hrishikesh Chandanpurkar, a hydrologist not involved in the study, describing the broader pattern of aquifer depletion the map revealed across multiple continents.
The finer resolution mattered because coarser, older satellite methods tend to blur sharp regional differences together, spreading a sharp local decline across a much wider area and making it look milder than it really is. The study found its regional trend estimates ran, on average, 33 percent larger than those produced by the older mascon approach, and for smaller regions under 100,000 square kilometers, the gap widened to 52 percent. The southern High Plains, a relatively compact aquifer system compared with something like the Amazon basin, falls squarely into the size range where the older method understated the problem most.
A 45 Percent Undercount in Earlier Estimates
The single most consequential number for water planners is the gap between old and new depletion estimates. Averaged across aquifers with significant human-driven groundwater loss, including the southern High Plains, prior studies had underestimated the rate of depletion by about 45 percent, the researchers found. O’Neill said the goal of the higher-resolution mapping was practical rather than purely academic: “Water managers and downstream communities need to know which aquifer is responsible for a given trend.”
The distinction matters most in places like the High Plains, where several states draw from the same underground reservoir but manage water rights separately under their own state laws. A 45 percent gap between the old and new depletion estimate is the difference between a state agency budgeting for a slow, manageable decline and one that discovers, years later, that the aquifer beneath its farms has been drawn down almost twice as fast as its own models assumed.
The Live Science report on the study lists other global hotspots identified by the same method, including northern India, southern Iran, California’s Central Valley, Pakistan’s Indus basin, North China and the Fertile Crescent, placing the High Plains loss inside a much larger global pattern rather than treating it as an isolated American problem.
A separate summary of the paper is catalogued through the National Library of Medicine’s PubMed index, and the full peer-reviewed text is available through PNAS. What the higher-resolution data leaves unresolved is how quickly the Southern High Plains Aquifer’s water table could stabilize even under aggressive conservation, since the underlying geology refills far slower than farms in the five states currently draw it down.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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