How climate change will affect western groundwater

February 17, 2016
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. Credit: David Stonestrom, U.S. Geological Survey

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.

"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 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 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Groundwater is already being withdrawn from the aquifers of California's Central Valley, the central and southern portions of the High Plains and Arizona's San Pedro faster than the groundwater is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.

The orange lines delineate the eight groundwater aquifers in the western US that a University of Arizona-led research team studied to examine how climate change will affect groundwater in the western US. Credit: University of Arizona department of hydrology

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 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.

Irrigation in the Amargosa Desert on the California/Nevada border uses water from the Death Valley Regional Aquifer. Credit: David Stonestrom, U.S. Geological Survey

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 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 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."

Explore further: Tropical groundwater resources resilient to climate change

More information: Thomas Meixner et al. Implications of projected climate change for groundwater recharge in the western United States, Journal of Hydrology (2016). DOI: 10.1016/j.jhydrol.2015.12.027

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8 comments

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mememine69
1 / 5 (7) Feb 18, 2016
CO2=Y2K²

The brick wall we are heading for is 35 more years of climate change debate and climate action delay to save the planet and these are the only things certain and unstoppable.
Was science also only 99% sure the planet wasn't flat?
Wanting science to have been certain made us all rednecks in our children's history books.

*Even Occupy no longer mentions CO2 in it's list of demands so follow the herd sheeple.
This was our Iraq War.
ContrarianInvestor
1 / 5 (3) Feb 19, 2016
UNFORTUNATELY, CLIMATE CHANGE GOALS WILL FAIL & EARTH IS DOOMED

President Obama & other world leaders, Al Gore, Lord Moncton, David Suzuki, Environmentalist & Climate Change proponents etc are fighting a losing battle.

Big Oil, Koch Brothers, David Tepper, paid off analysts, paid off lawyers & aggressive Short Sellers etc are working overtime to kill companies like SunEdison the largest global renewable energy company in the world.

Their stock tanked from $33.45 to $1.50 within 6 months due to oil price tanking & aggressive short selling (over 35% short interest), even though they have a huge back log of projects, $4.43 book value (PEG ratio 0.02, $1.4 billion equity & owns 2 Yield Cos TERP & GLBL but only $490 million market cap) & mostly strong buy recommendations from most analysts. It went from a $11 billion dollar market cap company to $500 million.
ContrarianInvestor
1 / 5 (3) Feb 19, 2016
Ironically, SunEdison tanked with the price of oil tanking when demand for oil is going down but demand for electricity is going up.

If investors keep losing on renewable energy investments & green companies go bankrupt, the Climate Change movement will die off along with Earth.

You can talk all you want but in reality, cash is king!
ContrarianInvestor
3 / 5 (4) Feb 19, 2016
Public Utilities Commission Chair Randy Iwase blasted Hawaiian Electric (HECO) for terminating a contract for three solar farms on Oahu. He threatened further investigation.

"When the utility kills cheaper renewable projects to announce new fossil fuel plants, it sounds bad. But worse, it could mean the utility is actually killing off competition from cheaper renewable generators that would have competed with its own fossil fuel plants which it wants to maximize profits from." - Rep. Chris Lee (D, Kailua-Waimanalo).
Porgie
1 / 5 (4) Feb 19, 2016
I think we should be asking : "Are we going to continue to allow California to suck the water away from the rest of the nation?" They have shown they are grossly irresponsible when it comes to managing resources. After all they put about 2 million tons of CO2 into the atmosphere every year and do nothing about global warming. California is the problem, stop issuing building permits and save our resources.
gkam
2.6 / 5 (5) Feb 20, 2016
As a former Plant Engineer for a large iron foundry in the Bay Area in the late 1970's, I can assure you everything changed when we tackled the pollution problem, and cleaned it up.

You might see how much clean power we produce, too. While I was in Technical Services for PG&E in the 1980's we were getting our power from disparate sources, trying them all for efficacy, efficiency, and applicability for generation assets. Our clean air laws are the strictest in the nation.

Where do you live?
Forestgnome
1 / 5 (1) Feb 21, 2016
Wet and dry regions occur as a result of climate and microclimate patterns, not warmer or colder weather. If, as they say, our climate is warming, all of those patterns are likely to change, and the localities of future wet or dry regions are essentially unpredictable with our current knowledge.
Vietvet
4.2 / 5 (5) Feb 21, 2016
Wet and dry regions occur as a result of climate and microclimate patterns, not warmer or colder weather. If, as they say, our climate is warming, all of those patterns are likely to change, and the localities of future wet or dry regions are essentially unpredictable with our current knowledge.


Current predictions is for dry areas to become drier and wet regions to become wetter. Those patterns are already taking place.

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