Tag: Groundwater

Colorado River Drought Triggers Unexpected Groundwater Collapse in the Upper Basin

Virginia Tech research (published in Water Resources Research) shows that recent severe drought in the Colorado River Basin has driven an unprecedented shift in groundwater depletion, with the historically more resilient Upper Basin now losing groundwater faster than the Lower Basin.

NASA’s GRACE (Gravity Recovery and Climate Experiment) satellites measure tiny changes in Earth’s gravity field to track how mass, especially water, moves around the planet.

GRACE’s strength is its ability to “weigh” large regions from space, capturing the total water mass change even where ground- based well networks are sparse.

A vast, arid landscape showcasing dry, cracked earth patterns, with steep rocky cliffs in the background and a thin body of water visible in the distance under a clear blue sky.
AI generated by Grok

Virginia Tech research (published in Water Resources Research) shows that recent severe drought in the Colorado River Basin has driven an unprecedented shift in groundwater depletion, with the historically more resilient Upper Basin now losing groundwater faster than the Lower Basin.

Declining river flows and falling levels in reservoirs like Lake Powell and Lake Mead are the visible signs of the long- running Southwestern megadrought. Underground, groundwater reserves- which supply a critical buffer for about 40 million people, agriculture, and ecosystems- are depleting rapidly, and the pattern has changed.

Historically, groundwater declined more in the Lower Basin (Arizona, southern Nevada, southeastern California). The system has now reached a turning point: the Upper Basin (Colorado, Wyoming, Utah, New Mexico) is experiencing rapid losses, with surface- water shortages increasingly affecting groundwater.

Researchers led by geosciences graduate student Esther Oyedele, working with assistant professor Susanna Werth and colleagues, isolated groundwater changes by combining NASA GRACE (Gravity Recovery and Climate Experiment) satellite measurements of total water storage with estimates of surface water, soil moisture, and snow-water storage for 2004- 2023.⁠

Key findings include:

  • Acceleration of groundwater depletion after 2019.
  • During the severe 2020- 2022 drought, the Upper Basin lost about 4.6 trillion gallons of groundwater, nearly double the Lower Basin’s estimated 2.5 trillion gallons.⁠

Oyedele noted: “We generally think of the Upper Basin as more resilient because of its snowmelt- driven recharge. I did not expect to see so much groundwater loss there during the recent drought. What surprised me even more was that groundwater did not track surface- water shortages in the same way in the Upper and Lower Basins.”

Groundwater and surface water are often connected; declining aquifers can reduce base flows into rivers, creating a feedback loop that worsens surface- water shortages. Continued depletion, especially in the Upper Basin, risks intensifying this cycle. Werth emphasized that managing surface water alone is no longer sufficient, protecting the basin requires treating water above and below ground as a connected resource.

The original study is available via DOI 10.1029/2025WR041695. The Virginia Tech news release by Kelly Izlar was published on October 13, 2026.

Map of the Colorado River Basin showing active management areas, irrigation zones, aquifers, reservoirs, and groundwater wells, with a small inset of the southwestern United States.
Map of the hydrogeological setting of the CRB and data applied in the study. Credit: Water Resources Research (2026). DOI: 10.1029/2025wr041695

NASA’s GRACE (Gravity Recovery and Climate Experiment) satellites measure tiny changes in Earth’s gravity field to track how mass, especially water, moves around the planet.

How GRACE works

GRACE does not take traditional “pictures” of Earth with cameras or radars pointed downward. Instead, the two nearly identical satellites themselves form the instrument.

  • The satellites fly in the same near- polar, low- Earth orbit (initially around 450- 500 km / 280, 310 miles altitude), one trailing the other by about 220 km (137 miles).
  • As they orbit, local variations in Earth’s gravity (caused by concentrations of mass below) pull on the lead satellite first, slightly speeding it up and increasing the distance to the trailing satellite. Moments later, the trailing satellite feels the same pull and the gap closes again.
  • A highly precise microwave ranging system (K/Ka-band) continuously measures these minuscule distance changes, to within about 1 micron (the diameter of a red blood cell, or roughly 1/100th the thickness of a human hair).
  • GPS receivers determine each satellite’s exact position relative to Earth. Onboard accelerometers measure non- gravitational forces (atmospheric drag, solar radiation pressure, etc.) so scientists can isolate only the gravitational effects.
  • Star trackers keep track of the satellites’ orientation.

From these data, scientists produce monthly maps of Earth’s gravity field. Differences between months reveal where mass has been added or removed.

What the measurements reveal

Because water has mass, changes in the amount of water stored on or below the surface alter local gravity. GRACE (and its successor GRACE- FO) can therefore detect:

  • Groundwater depletion or recharge in aquifers
  • Changes in soil moisture
  • Snow and ice mass loss or gain (glaciers, ice sheets)
  • Surface- water variations in large lakes, reservoirs, and rivers
  • Ocean mass changes related to sea- level rise and currents

The original GRACE mission flew from 2002 to 2017. GRACE Follow-On (GRACE-FO) launched in 2018 and continues the record (with an added experimental laser ranging interferometer for even higher precision). Together they provide a continuous multi- decade view of terrestrial water storage changes.

Relevance to the Colorado River Basin study

In the recent Virginia Tech research, scientists used GRACE/GRACE -FO total water storage data and subtracted independent estimates of surface water, soil moisture, and snow water. The remaining signal isolates groundwater storage changes. This is how they quantified the unexpected rapid groundwater losses in the Upper Basin during the 2020- 2022 drought.

GRACE’s strength is its ability to “weigh” large regions from space, capturing the total water mass change even where ground- based well networks are sparse.

Its spatial resolution is relatively coarse (typically hundreds of kilometers), so it is best for basin- or regional -scale studies rather than individual wells.

Figure (a): Cumulative distribution function of GWSIDI showing probability decrease with increasing values.
Example statistical copula model for bivariate comparison of GWSDI and SWSDI. —
Contrasting Groundwater Response to Surface Water Shortages in the Upper and Lower Colorado River Basins – Oyedele – 2026 – Water Resources Research – Wiley Online Library

Contrasting Groundwater Response to Surface Water Shortages in the Upper and Lower Colorado River Basins

Key findings from the abstract and plain- language summary

  • The study analyzes basin-scale terrestrial water storage and groundwater storage in the Colorado River Basin (CRB) from water year 2004- 2023 using GRACE/GRACE-FO satellite observations combined with hydrological datasets.
  • There has been sustained basin- wide groundwater depletion over two decades, with accelerated losses since 2019, especially during the severe 2020- 2022 drought.
  • During that recent drought:
    • Upper Colorado River Basin (UCRB) lost 17.5 ± 3.5 km³ of groundwater.
    • Lower Colorado River Basin (LCRB) lost 9.4 ± 6.5 km³.
    • (These volumes convert to roughly 4.6 trillion gallons in the Upper Basin and 2.5 trillion gallons in the Lower Basin, matching the press release figures.)
  • A copula- based statistical framework was used to quantify probabilistic relationships between storage- based drought indicators and to characterize groundwater- surface water interactions.
    • In the Upper Basin, there is strong coupling between surface- water deficits and groundwater drought probability (groundwater losses closely track surface- water shortages).
    • In parts of the Lower Basin, the statistical dependence is weaker, groundwater declines can occur somewhat independently of surface-water conditions, consistent with chronic human extraction under limited supply.

Broader context and implications

Groundwater is a critical buffer in the CRB, which supplies water to ~40 million people and extensive agriculture. The Upper Basin has traditionally been viewed as more resilient due to snowmelt-driven recharge, but the recent drought revealed greater vulnerability there. Continued depletion risks reducing groundwater contributions to river baseflow and intensifying feedback loops between groundwater loss and surface-water shortages.

The authors emphasize the value of satellite monitoring for large managed river basins and call for integrated water- management strategies that address both climatic pressures and sustained anthropogenic demand (above and below ground).

The full paper includes maps of the hydrogeological setting, GRACE mascon analysis, well data, and detailed statistical results. You can access the open- access version (including PDF download) directly at the DOI link above.

Journal: Water Resources Research,  (Volume 62, Issue 10)

DOI: 10.1029/2025wr041695

Provided: Virginia Tech

First published: 13 October 2026 (Open Access)

Authors:  E. O. Oyedele, S. Werth, G. Carlson (and others)

Abstract

Groundwater plays a critical role in sustaining the water supply in the Colorado River Basin (CRB), a region experiencing persistent drought, population growth, and increasing water demand. Using GRACE/GRACE-FO satellite observations combined with hydrological data sets, we analyze basin-scale variations and long-term trends in terrestrial and groundwater storage across the CRB from water year 2004–2023. We further apply a joint framework integrating copula-based statistical modeling with statistical inference to quantify probabilistic relationships among storage-based drought indicators and to characterize groundwater–surface water interactions. Results reveal sustained basin-wide groundwater depletion over the past two decades, with accelerated losses since 2019 and during the water year 2020–2022 drought. Notably, during this recent drought period, groundwater losses were larger in the typically more resilient Upper CRB (17.5 ± 3.5 km3) than in the Lower CRB (9.4 ± 6.5 km3), indicating increasing vulnerability across both subbasins. Copula-based analysis shows strong coupling between surface-water deficits and groundwater drought probability in the Upper CRB, whereas parts of the Lower CRB exhibit weaker statistical dependence, consistent with groundwater extraction operating partly independently of surface water availability under chronically limited supply conditions. These findings provide a basin-wide observational synthesis of groundwater–surface water dynamics and demonstrate the value of satellite-based monitoring for diagnosing hydroclimatic stress in large managed river basins. The results highlight emerging shifts in groundwater vulnerability across the CRB and underscore the need for integrated water-management strategies that jointly consider climatic pressures and sustained anthropogenic demand.

Study: Underground car parks heat up groundwater

These underground car parks are heated by waste heat from car engines and are typically several degrees warmer than the surrounding subsurface, which makes them a heat source for ambient subsurface and groundwater.

From Watts Up With That?

From the “especially if the EV’s are on fire” department…

The heat given off by car engines warms up underground car parks in such a way that the heat passes through the ground into the groundwater. In Berlin alone, enough energy is transferred to the groundwater to supply 14,660 households with heat. This finding was made by a team from Martin Luther University Halle-Wittenberg (MLU), the Karlsruhe Institute of Technology, and the University of Basel. According to the researchers, this warming could have long-term effects on groundwater quality. In their study, published in the journal Science of The Total Environment, they also propose a solution. Using geothermal energy and heat pumps, the heat could be extracted from the ground and utilized.

The researchers examined temperatures in 31 underground car parks in various cities throughout Germany, Austria and Switzerland. In six of them, they were also able to measure the temperature of the groundwater in the immediate vicinity. This allowed a heat profile to be created for all locations. Their investigations showed that underground car parks heat up the groundwater throughout the year. The volume of traffic in the underground car parks, their proximity to the groundwater and ambient groundwater temperatures were the biggest influencing factors. “Public underground car parks heat up the groundwater more than private facilities as they are often deeper and the cars park there for shorter periods of time,” explains Maximilian Noethen, a geoscientist from MLU. 

According to the team, geothermal energy and heat pumps could help utilise the excess heat in the ground. “This would have the advantage of extracting energy from the groundwater and thus cooling it down,” says Noethen. Based on modelling for 5,040 underground car parks in Berlin, the team calculated groundwater warming from the underground car parks for the city. Since many underground car parks in the central districts of the capital are located in or near groundwater, a particularly large amount of heat is transferred to the groundwater there. According to their calculations, around 0.65 petajoules of energy are emitted annually in Berlin. This could theoretically supply around 14,660 households with heat. “Of course, heat from groundwater alone is not enough to cover the heating needs of a city like Berlin or even a country like Germany. Nor are the temperature levels of the groundwater near the surface high enough to provide heat without a heat pump. However, we do know from previous studies that the potential for geothermal energy goes well beyond this and that it could make a significant contribution to supplying sustainable heat,” says Professor Peter Bayer from the Institute of Geosciences and Geography at MLU. 

Groundwater temperatures have been rising for decades as a result of global warming. In cities, this is exacerbated by dense urban development, soil sealing, lack of vegetation and heat radiating directly from tunnels and underground car parks. Since the organisms in the groundwater are adapted to constant temperatures, species composition could also change. “This could affect the quality of the groundwater from which we draw large parts of our drinking water. This development needs to be controlled through a variety of measures,” concludes Bayer. 

The study was funded by the Deutsche Bundesstiftung Umwelt (DBU) and the Margarete von Wrangell Program of the Ministry of Science, Research and the Arts of the State of Baden-Württemberg.  

Study: Noethen M. et al. Thermal impact of underground car parks on urban groundwater. Science of The Total Environment (2023). doi: 10.1016/j.scitotenv.2023.166572

Claim: We’ve Pumped So much Groundwater that We’ve Nudged the Earth’s Spin

The shifting of mass and consequent sea level rise due to groundwater withdrawal has caused the Earth’s rotational pole to wander nearly a meter in two decades

From Watts Up With That?

The shifting of mass and consequent sea level rise due to groundwater withdrawal has caused the Earth’s rotational pole to wander nearly a meter in two decades

Peer-Reviewed Publication

AMERICAN GEOPHYSICAL UNION

IMAGE: HERE, THE RESEARCHERS COMPARE THE OBSERVED POLAR MOTION (RED ARROW, “OBS”) TO THE MODELING RESULTS WITHOUT (DASHED BLUE ARROW) AND WITH (SOLID BLUE ARROW) GROUNDWATER MASS REDISTRIBUTION. THE MODEL WITH GROUNDWATER MASS REDISTRIBUTION IS A MUCH BETTER MATCH FOR THE OBSERVED POLAR MOTION, TELLING THE RESEARCHERS THE MAGNITUDE AND DIRECTION OF GROUNDWATER’S INFLUENCE ON THE EARTH’S SPIN. view more CREDIT: SEO ET AL. (2023), GEOPHYSICAL RESEARCH LETTERS

American Geophysical Union
15 June 2023
Release No. 23-25
For Immediate Release

This press release is available online at: https://news.agu.org/press-release/weve-pumped-so-much-groundwater-that-weve-nudged-the-earths-spin

AGU press contact:
Rebecca Dzombak, news@agu.org (UTC-4 hours)

Contact information for the researchers:
Ki-Weon Seo, Seoul National University, seokiweon@snu.ac.kr (UTC+9 hours)

WASHINGTON — By pumping water out of the ground and moving it elsewhere, humans have shifted such a large mass of water that the Earth tilted nearly 80 centimeters (31.5 inches) east between 1993 and 2010 alone, according to a new study published in Geophysical Research Letters, AGU’s journal for short-format, high-impact research with implications spanning the Earth and space sciences.

Based on climate models, scientists previously estimated humans pumped 2,150 gigatons of groundwater, equivalent to more than 6 millimeters (0.24 inches) of sea level rise, from 1993 to 2010. But validating that estimate is difficult.

One approach lies with the Earth’s rotational pole, which is the point around which the planet rotates. It moves during a process called polar motion, which is when the position of the Earth’s rotational pole varies relative to the crust. The distribution of water on the planet affects how mass is distributed. Like adding a tiny bit of weight to a spinning top, the Earth spins a little differently as water is moved around.

“Earth’s rotational pole actually changes a lot,” said Ki-Weon Seo, a geophysicist at Seoul National University who led the study. “Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole.”

Water’s ability to change the Earth’s rotation was discovered in 2016, and until now, the specific contribution of groundwater to these rotational changes was unexplored. In the new study, researchers modeled the observed changes in the drift of Earth’s rotational pole and the movement of water — first, with only ice sheets and glaciers considered, and then adding in different scenarios of groundwater redistribution.

The model only matched the observed polar drift once the researchers included 2150 gigatons of groundwater redistribution. Without it, the model was off by 78.5 centimeters (31 inches), or 4.3 centimeters (1.7 inches) of drift per year.

“I’m very glad to find the unexplained cause of the rotation pole drift,” Seo said. “On the other hand, as a resident of Earth and a father, I’m concerned and surprised to see that pumping groundwater is another source of sea-level rise.”

“This is a nice contribution and an important documentation for sure,” said Surendra Adhikari, a research scientist at the Jet Propulsion Laboratory who was not involved in this study. Adhikari published the 2016 paper on water redistribution impacting rotational drift. “They’ve quantified the role of groundwater pumping on polar motion, and it’s pretty significant.”

The location of the groundwater matters for how much it could change polar drift; redistributing water from the midlatitudes has a larger impact on the rotational pole. During the study period, the most water was redistributed in western North America and northwestern India, both at midlatitudes.

Countries’ attempts to slow groundwater depletion rates, especially in those sensitive regions, could theoretically alter the change in drift, but only if such conservation approaches are sustained for decades, Seo said.

The rotational pole normally changes by several meters within about a year, so changes due to groundwater pumping don’t run the risk of shifting seasons. But on geologic time scales, polar drift can have an impact on climate, Adhikari said.

The next step for this research could be looking to the past.

“Observing changes in Earth’s rotational pole is useful for understanding continent-scale water storage variations,” Seo said. “Polar motion data are available from as early as the late 19th century. So, we can potentially use those data to understand continental water storage variations during the last 100 years. Were there any hydrological regime changes resulting from the warming climate? Polar motion could hold the answer.”

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Notes for journalists:

This study is published in Geophysical Research Letters, a fully open-access journal. View and download a pdf of the study here.

Paper title:

“Drift of the Earth’s pole confirms groundwater depletion as a significant contributor to global sea level rise 1993-2010”

Authors:

  • Ki-Weon Seo (corresponding author), Center for Educational Research and Department of Earth Science Education, Seoul National University, Seoul, Republic of Korea
  • Jae-Seung Kim, Kookhyoun Youm, Department of Earth Science Education, Seoul National University, Seoul, Republic of Korea
  • Dongryeol Ryu, Department of Infrastructure Engineering, The University of Melbourne, Parkville, Australia
  • Jooyoung Eom, Department of Earth Science Education, Kyungpook National University, Daegu, Republic of Korea
  • Taewhan Jeon, Center for Educational Research, Seoul National University, Seoul, Republic of Korea
  • Jianli Chen, Department of Land Surveying and Geo-informatics, and Research Institute for Land and Space, Hong Kong Polytechnic University, Hong Kong
  • Clark Wilson, Department of Geological Sciences, and Center for Space Research, University of Texas at Austin, Austin, TX, USA

JOURNAL

Geophysical Research Letters

DOI

10.1029/2023GL103509 

ARTICLE TITLE

“Drift of the Earth’s pole confirms groundwater depletion as a significant contributor to global sea level rise 1993-2010”

ARTICLE PUBLICATION DATE

15-Jun-2023

From EurekAlert!