By 2050 climate change will increase the groundwater deficit even more for four economically important aquifers in the western U.S., reports a University of Arizona-led team of scientists.
The new report is the first to integrate scientists' knowledge about groundwater in the U.S. West with scientific models that show how climate change will affect the region.
Water can reach and recharge a groundwater aquifer various ways. Precipitation can percolate directly into the aquifer; water from streams and runoff can percolate into the aquifer; water from irrigating crops can percolate deep into the soil; and water from melting snowpack and from mountain streams can flow into the valley below and then percolate into the aquifer.
Image courtesy of David Stonestrom, U.S. Geological Survey
"We wanted to know, 'What are the expectations for increases and decreases in groundwater as we go forward in this century?'" said lead author Thomas Meixner, a UA professor and associate department head of hydrology and water resources. "In the West, 40 percent of the water comes directly from groundwater."
Climate models predict that in general, wet regions will become wetter and dry regions will become drier. The Southwest is expected to become drier and hotter.
"Aquifers in the southern tier of the West are all expected to see slight-to-significant decreases in recharge as the climate warms," Meixner said.
Groundwater is already being withdrawn from the aquifers of California's Central Valley, the central and southern portions of the High Plains and Arizona's San Pedro faster than the groundwater is being recharged.
Climate change will make the groundwater deficits worse in those aquifers, the researchers report.
For the Death Valley and Wasatch Front aquifers, the effect of climate change on the balance between usage and recharge isn't so predictable.
In contrast, western aquifers at about the latitude of Boulder, Colorado and further north are likely to be recharged faster than people withdraw the water, the team reports. The northern aquifers the researchers studied are the northern High Plains, the Spokane Valley, the Williston Basin and the Columbia plateau.
"In the long term, pumping has to equal recharge. You can get there through slow social adjustment. You could slowly decrease water withdrawal by conservation and efficiency," Meixner said. "Or you can hit bottom and have farm abandonment and dry wells."
"It's a social decision as to who gets the water," Meixner said. "The southern regions of the western U.S. must be prepared to adapt to a much drier future."
The team's research article, "Implications of projected climate change for groundwater recharge in the western United States," is now online and is scheduled for publication in the March issue of the Journal of Hydrology. UA Associate Professor of Atmospheric Sciences Christopher Castro is a co-author. A list of all seventeen authors is at the bottom of this release.
The report is an outgrowth of a workshop held at the U.S. Geological Survey's John Wesley Powell Center for Analysis and Synthesis. The National Science Foundation and USGS funded the workshop.
To synthesize existing knowledge and predict how climate change would affect western groundwater, Meixner gathered 16 experts in climate change and in hydrology of the western U.S.
Predictions at the major river basin or several-state level can be useful for developing water policy, the team wrote. However, the team found predictions from existing studies were either at a global scale or at the local level, not at the regional level.
To create regional-scale predications, the scientists synthesized existing studies and applied current knowledge of recharge processes. The team studied eight economically important western aquifers for which studies about their groundwater recharge budgets existed. In addition, models of how climate change would affect recharge were available for four of the aquifers.
To compare all eight aquifers, the team developed a uniform classification scheme for the components of groundwater recharge. The scientists identified four different components of groundwater recharge: diffuse, focused, irrigation and mountain system.
Some types of recharge are more easily affected by human behavior and water policy than others. Human decision-making can easily affect irrigation recharge, water that percolates deep into the soil from irrigating crops, and focused recharge, water that reaches the groundwater from streams or runoff.
In contrast, human behavior has a much smaller effect on diffuse and mountain-systems recharge. Diffuse recharge comes from the precipitation that falls on a specific spot and then percolates down into the groundwater.
Much of the mountain-systems recharge comes from snowpack, Meixner said. As the snow melts, the water fills mountain streams which end up in the flatlands below. Snowmelt can also percolate into the soil and eventually reach the valley below as the water moves downhill through the bedrock underlying the mountains.
The San Pedro aquifer in southeastern Arizona is one example of an aquifer where the human use of groundwater will increasingly outstrip recharge as the climate warms, the researchers report. Much of the San Pedro's current recharge comes from mountain-system recharge, which the scientists expect will dwindle as more precipitation falls in the mountains as rain rather than snow and as the region dries.
When more groundwater is pumped than is replaced by recharge, rivers can be sucked dry, as happened to the Santa Cruz River in Tucson, Meixner said. Once the Santa Cruz flowed year-round; now in Tucson the river has water only after heavy rains.
"What you would expect to see is that climate change will exacerbate problems in the Southwest on the recharge end," Meixner said.
"Our study reveals that the western U.S. needs to redouble efforts to manage water resources to maximize benefits to individuals and society," he said. "We can't be wasting water."
Author list for "Implications of projected climate change for groundwater recharge in the western United States."
Thomas Meixner, University of Arizona, Tucson; Andrew H. Manning, U.S. Geological Survey, Denver; David A. Stonestrom, USGS Menlo Park, California; Diana M. Allen, Simon Fraser University, Burnaby, British Columbia, Canada; Hoori Ajami, University of New South Wales, Sydney, Australia; Kyle W. Blasch, USGS, Boise, Idaho; Andrea E. Brookfield, Kansas Geological Survey, Lawrence; Christopher L. Castro,University of Arizona; Jordan F. Clark, University of California, Santa Barbara; David J. Gochis, National Center for Atmospheric Research, Boulder, Colorado; Alan L. Flint USGS, Sacramento, California; Kirstin L. Neff and Rewati Niraula, University of Arizona; Matthew Rodell, NASA Goddard Space Flight Center, Greenbelt, Maryland; Bridget R. Scanlon, University of Texas, Austin; Kamini Singha, Colorado School of Mines, Golden; Michelle A. Walvoord USGS, Denver.
USGS John Wesley Powell Center for Analysis and Synthesis
Mari N. Jensen
Mari N. Jensen | EurekAlert!
As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation
29.03.2017 | University of Hawaii at Manoa
Researchers discover dust plays prominent role in nutrients of mountain forest ecoystems
29.03.2017 | University of Wyoming
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Materials Sciences
29.03.2017 | Physics and Astronomy
29.03.2017 | Earth Sciences