In most cases,
water issues are local or regional. The same is generally true of groundwater
depletion and overproduction. Groundwater resources are distributed according
to geology and vary considerably by geographic region. The new paper in Science
Advances is a global study that highlights some potential global effects of
groundwater depletion, such as its surprisingly large contribution to sea level
rise. Environmentalists have long portrayed overuse of groundwater resources as
potentially catastrophic. It certainly can be in certain places. While probably
not as catastrophic as depicted by environmentalists, groundwater depletion is
a problem that tends to increase over time since the rate of discharge is much
greater than the rate of recharge. One thing that could further decrease
recharge rates is soil moisture loss, which is also well-documented. The causes
of soil moisture loss, which I wrote about in May
2025, are mainly atmospheric, changes in evapotranspiration, and precipitation.
However, without adequate soil moisture, there is less water to recharge
aquifers.
A long piece by ProPublica
about the study describes the main issue of concern:
“… {the study} concludes not only that Earth is suffering a
pandemic of “continental drying” in lower latitudes, but that it is the
uninhibited pumping of groundwater by farmers, cities and corporations around
the world that now accounts for 68% of the total loss of fresh water in those
areas…”
The study, by researchers at
Arizona State University, examines 22 years of observational data from NASA’s
Gravity Recovery and Climate Experiment, or GRACE, satellites, which measure
changes in the mass of the Earth and have been applied to estimate its water
content.
Some of the startling
conclusions from the paper include that the continental drying exceeded the
rates of glacier and ice sheet melting, which means more water for sea level
rise is coming from groundwater, evaporation, and changes in precipitation
patterns than from melting glaciers. While global warming may be triggering and
exacerbating these issues, it is not the direct cause. If groundwater depletion
(via pumping and soil moisture loss) is a bigger cause of sea level rise than
glacier melting, then the effects of temperature on glacier melting may have
been overestimated. The tipping point for continental drying exceeding glacier
and ice sheet melt was around 2014-2015, according to the study. The authors
had done previous work on terrestrial water storage (TWS). They have termed
global TWS reductions as “continental drying.”
As noted in the abstract
below, “dry areas are now drying faster than wet areas are wetting.”
This is creating what they are calling “mega-drying” regions that continue to
expand at an alarming rate.
The authors note that as
surface water resources are depleted, there is more production of groundwater
resources. As shallower groundwater aquifers are depleted, deeper ones are
tapped. Citing several sources, they note that the problem is:
“…exacerbated by global shortcomings in groundwater
management and which amplifies rates of TWS loss through a positive feedback.
The consequences of global groundwater depletion include reduced irrigation
water supply and threats to agricultural productivity, reduced capacity for
climate adaptation, drought resilience and for growth in desert cities, reduced
biodiversity (24) and damage to groundwater dependent ecosystems, decreasing
access as water tables fall, and many others.”
They note that about 75% of
the global population lives in the 101 countries that have been losing
freshwater since 2002. Southwestern North America, Central America, Alaska, the
Canadian Archipelago, and Patagonia, much of the Middle East/North
Africa/Pan-Eurasia, high-latitude Canada, and northern Eurasia are among the
new mega-drying regions.
More geospatial data and
comparisons of wetting and drying from the paper are shown below.
A 2021 study in the journal
Science suggested that 6-20% of groundwater wells globally are at risk of
depletion, as noted in the abstract below
“Groundwater wells supply water to billions of people,
but they can run dry when water tables decline. Here, we analyzed construction
records for similar to 39 million globally distributed wells. We show that 6 to
20% of wells are no more than 5 meters deeper than the water table, implying
that millions of wells are at risk of running dry if groundwater levels decline
by only a few meters. Further, newer wells are not being constructed deeper
than older wells in some of the places experiencing significant groundwater
level declines, suggesting that newer wells are at least as likely to run dry
as older wells if groundwater levels continue to decline. Poor water quality in
deep aquifers and the high costs of well construction limit the effectiveness
of tapping deep groundwater to stave off the loss of access to water as wells
run dry.”
The abstract of another 2021
paper about groundwater depletion by one of the authors of the current paper explains the problem, based on the previous 2021 paper by Jasechko and Perrone,
noted above.
Long-term trends in TWS by country are
shown below.
The authors calculate that
68% of TWS reduction is attributable to groundwater depletion. Surface water
depletion makes up 18%, soil moisture loss makes up 9%, and snow water
equivalent makes up 5%. Thus, the TWS reduction problem is mostly a groundwater
depletion issue.
Below are the estimated
contributions of TWS loss to sea level rise.
The authors note that better
groundwater management is imperative if we are to preserve these precious
resources:
“Key management decisions and new policies, especially
toward regional and national groundwater sustainability, and international
efforts, toward global groundwater sustainability, can help preserve this
precious resource for generations to come. Simultaneously, such actions will
slow rates of sea level rise.”
“We hope that the findings of this work will serve to
raise awareness of the urgent, global need to prepare for shrinking freshwater
availability on land; greater vulnerability to sea level rise along coastal
regions; and the interconnected, widespread impacts of continental drying on
people, the environment, and the economy. Major coordinated, national,
international, and global, transdisciplinary efforts are critically needed to
elevate the level of awareness and action around continental drying and decreasing
freshwater availability to that of the carbon cycle.”
In the methodology section,
the authors show how they calculated TWS and separated it into its snow-water
equivalent, surface water, soil moisture, and groundwater components.
The ProPublica article cites
activist environmentalist scientist Peter Gleick, who says that groundwater
overpumping is severely threatening food production, since 70% of groundwater
is used for agriculture. I doubt that the issue is severe yet since it would
mainly affect drier areas. Gleick has documented the social effects of droughts
and groundwater depletion on things like conflict and migration. There is a
need for better water management. California has implemented some policies and
standards, but many think they are not acting fast enough to preserve
groundwater. Groundwater management needs to be considered everywhere, but
especially where aquifers are scarce and vulnerable to depletion, and where it
is dry.
Land Subsidence Due to Groundwater Withdrawal is a Major
Problem in Many Cities
I remember how the flooding
in Houston from 2017’s Hurricane Harvey was exacerbated by land subsidence due
to groundwater withdrawal. The ProPublica article mentions Mexico City and
large parts of China, Indonesia, Spain, and Iran as places at high risk for
continued subsidence. A 2025 study in Nature Cities concludes that 28 cities
across the United States are sinking, including New York, Houston, and Denver.
As noted in the paper’s abstract below, the problem is creating very
significant risks to urban infrastructure.
The paper highlights some
groundwater management actions that could help reduce the problem. They involve
mitigating the problem with more land use restrictions, groundwater recharge,
and engineering solutions such as structural reinforcement and soil compaction,
and adapting to the problem by not building or building differently in
high-risk areas. Unfortunately, this problem of urban land subsidence due to
groundwater withdrawal is likely to increase, so cities need to become better
prepared to handle the problem.
References:
The
Drying Planet. Abrahm Lustgarten, Graphics by Lucas Waldron, Illustrations by
Olivier Kugler for ProPublica. July 25, 2025. Global
Water Supplies Threatened by Overmining of Aquifers: New Study — ProPublica
New
global study shows freshwater is disappearing at alarming rates. Sandy Keaton
Leander. Phys.org. July 25, 2025. New
global study shows freshwater is disappearing at alarming rates
Unprecedented
continental drying, shrinking freshwater availability, and increasing land
contributions to sea level rise. Hrishikesh A. Chandanpurkar, James S.
Famiglietti, Kaushik Gopalan, David N. Wiese, Yoshihide Wada, Kaoru Kakinuma,
John T. Reager, and Fan Zhang. Science Advances. 25 Jul 2025. Vol 11, Issue 30.
DOI: 10.1126/sciadv.adx0298. Unprecedented
continental drying, shrinking freshwater availability, and increasing land
contributions to sea level rise | Science Advances
Global
groundwater wells at risk of running dry. Scott Jasechko and Debra Perrone. SCIENCE.
Volume372. Issue 6540. Page418-+DOI10.1126/science.abc2755. April 23, 2021. Global
groundwater wells at risk of running dry-Web of Science Core Collection
The
hidden crisis beneath our feet: Disappearing groundwater requires action to
prevent widespread water scarcity. James S. Famiglietti and Grant Ferguson. Science.
23 Apr 2021. Vol 372, Issue 6540. pp. 344-345. The hidden crisis
beneath our feet | Science
Land
subsidence risk to infrastructure in US metropolises. Leonard O. Ohenhen, Guang
Zhai, Jonathan Lucy, Susanna Werth, Grace Carlson, Mohammad Khorrami, Florence
Onyike, Nitheshnirmal Sadhasivam, Ashutosh Tiwari, Khosro Ghobadi-Far, Sonam F.
Sherpa, Jui-Chi Lee, Sonia Zehsaz & Manoochehr Shirzaei. Nature Cities
volume 2, pages543–554 (2025). Land subsidence risk
to infrastructure in US metropolises | Nature Cities
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