USGS finds vast reserves of salty water underground in California
By Devika G. Bansal | dbansal@bayareanewsgroup.com |
PUBLISHED: April 15, 2017 at 4:36 pm | UPDATED: April 17, 2017 at 4:59 am
A new nationwide study has unearthed the huge hidden potential of tapping into salty aquifers as a way to relieve the growing pressure on freshwater supplies across the United States.
Digging into data from the country’s 60 major aquifers, the U.S. Geological Survey reports that the amount of brackish — or slightly salty — groundwater is more than 35 times the amount of fresh groundwater used in the United States each year.
Supplies exist in every state except New Hampshire and Rhode Island, with the largest reserves in the central U.S. In the Golden State, the California Coastal Basin and Central Valley aquifers together contain close to 7 billion acre-feet of brackish water, which if desalinated could provide enough water for the state’s needs for the next 160 years.
Untreated brackish water can replace fresh water for some uses, but would have to be desalinated for municipal use. A recent study by the Oakland-based Pacific Institute found that the costs of doing that were competitive with other methods of adding water capacity.
“This is a big leap for the water sector,” said Newsha Ajami, director of urban water policy at Stanford University’s Water in the West program. “It’s amazing we have so much capacity now to map and measure.”
Finding evidence of more than 800 times the amount of brackish groundwater the U.S. currently uses, the study provides a starting point for more in-depth local analyses.
“The use of brackish groundwater has been growing since the 1970s,” said Jennifer Stanton, a USGS hydrologist and lead author of the study. “Our goal was to determine the data gaps so we know enough about the resource to use it sustainably.”
Brackish water contains dissolved minerals ranging from 1,000 to 10,000 milligrams per liter. But the salinity doesn’t matter too much for the mining and oil and gas industries, which have been the biggest users of untreated brackish groundwater. The salty cousin of fresh water also finds favor with many livestock species that can drink brackish water in the lower concentration range, as well as with carefully managed salt-tolerant crops. When it comes to using brackish water for municipal use, however, the U.S. Environmental Protection Agency follows higher standards that entail treatments to remove salts.
Texas, California and Florida lead the pack with the most number of brackish groundwater desalination plants.
In the Bay Area, the Alameda County Water District has one such facility in Newark that has been desalting about 14,000 acre-feet of water annually since 2003 — about 40 percent of the water supplied by the district. There are currently two dozen brackish desalination facilities in California producing a total of 80,000 acre-feet of water annually. That’s a year’s worth of water for 400,000 people. The dry state of Texas has 46 inland brackish desalination facilities producing similar amounts — and hopes to develop more.
“The thing that surprised me is just how much interest there is in obtaining updated information about brackish groundwater resources,” Stanton said.
The report is expected to spark more discussion because it lays out the depths at which the water exists, salt concentrations, water volumes and aquifer features that make them easy or difficult to tap.
Although California just had one of its wettest years on record, experts warn that the situation could quickly change. “Yes, we have had one year of flooding and a lot of rain, but it doesn’t mean that in a year or two we’re not going to go back to drought conditions,” Ajami said.
That means local and regional water agencies must continue to develop a variety of water supplies to make themselves more secure during the drought years, said Rich Mills, chief of the water recycling and desalination section at the California Department of Water Resources. “You want to make sure different regions have diverse water supply portfolios, which means that if one falls short, you have another one to rely on,” added Ajami.
In that light, water agencies will continue to look to California’s vast salty aquifers to make their overall water supply more resilient, Mills said. Three new brackish desalination plants are under construction in the state, and at least 17 more are being planned — one of which will be located in an unincorporated area of Monterey County just north of Marina. All of the other projects will be located in Southern California. Also, an alliance of Bay Area water agencies has plans for a large plant in Pittsburg, with the potential to desalt brackish water from the Delta and deliver 23,000 acre-feet of water a year.
Despite the interest, however, it is unclear how sustainable it will be to pump the vast resource because of real concerns about groundwater overuse and land subsidence — the Central Valley being a prime example. Aquifers in the highly productive agricultural region have a lot of clay. “When we take water out of layers that are mostly clay, they squish and you lose the pore space forever,” said Rob Jackson, an earth scientist at Stanford.
“People in the Central Valley are using groundwater from deeper and deeper layers,” added Jackson, who published a California groundwater map last year. “If we’re going to use
Sample taps inside Sand City’s desalination plant test membranes that remove salt from brackish water. (Luke Gianni/California American Water) groundwater, we’ve got to think about where the subsidence will occur and pump groundwater from somewhere else.”
Recharging the aquifers is also an issue. Deeper layers contain ancient water that can take hundreds of thousands of years to refresh naturally, so using the resource would be highly unsustainable.
“If the agencies are going to be pumping brackish water out, they also have to manage how it will recharge over time,” said Rich Juricich, principal engineer in charge of sustainable groundwater at the California Department of Water Resources.
One of the ways toward groundwater sustainability is to replenish aquifers artificially by injecting water into them or by allowing water to trickle down through ponds and trenches. “There’s an opportunity to do more managed recharge in California to capture some of the runoff water and store it underground for use and also to recharge the aquifers,” Jackson said.
The USGS report, he and other experts say, is a promising start in pinpointing areas where brackish water could become a sustainable resource for many communities.
“There’s a lot of usable groundwater under our feet in California,” Jackson said, “as long as we’re careful about where and how we use it.”
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Large Aquifers Discovered Under California's Drought-Stricken Central Valley
By Bobby Magill, Climate Central
Jun 28 2016 09:00 AM EDT
Giant Pools of Water Found Underneath California
Meteorologist Danielle Banks is talking about aquifers buried thousands of feet below the ground that could be a game changer for drought-stricken California.
California’s Central Valley has three times more freshwater in underground aquifers than previously thought, drinking water that could help the state weather future drought and fortify itself against a changing climate, according to a new Stanford University study.
But tapping that water, locked thousands of feet beneath the ground, will be expensive and comes with an enormous risk — it could cause the valley floor to sink, according to the study, published Monday in the Proceedings of the National Academy of Sciences. Sinking land in the Central Valley is threatening roads, homes and other infrastructure, and reduces the amount of water some aquifers can hold.
“It’s not often that you find a ‘water windfall,’ but we just did,” said study co-author Rob Jackson, an earth system science professor at Stanford University. “California’s already using an increasing amount of groundwater from deeper than 1,000 feet. Our goal was to estimate how much water is potentially available.”
California's parched Central Valley in 2014. (Stuart Rankin/NASA/flickr)
Climate change is exposing the state to a greater threat of drought, reducing the amount of water available for farming and drinking as higher temperatures evaporate reservoirs. More precipitation is expected to fall as rain instead of snow in California as the world warms, forcing the state to find new ways to store rainwater for municipal and agricultural use.
To stave off losses during its four-year drought, California has relied on groundwater to irrigate its farm fields. So much groundwater is being used that the water table has fallen by 50 feet in some places in the Central Valley, and the valley floor is sinking, or subsiding, as aquifers are depleted.
Land subsidence, which has been occurring in the valley for decades because of groundwater pumping, has accelerated to two inches per month in some places, according to NASA. Sinking land threatens roads, bridges, aqueducts, buildings and other infrastructure as the land collapses beneath them.
The California drought has forced cities to cut back on water use. (Kevin Cortopassi/flickr)
Most of the groundwater comes from aquifers less than 1,000 feet deep. Deeper aquifers are usually considered too salty to be used for drinking or irrigation, requiring costly desalination and drilling operations to access them.
Analyzing water data gathered from oil and gas wells across eight Central Valley counties, the Stanford researchers show that there are about 2,700 cubic kilometers of accessible fresh or brackish water locked in the Central Valley’s deep underground aquifers. That’s almost triple the 1,020 cubic kilometers of freshwater that had been previously estimated.
Farming in California consumes between 25 million and 33 million acre-feet of water annually, or between 31 and 40 cubic kilometers of water, according to a 2015 Congressional Research Service report. A cubic kilometer of water is roughly equivalent to 1.3 times Los Angeles’ annual water use.
Some of the water that Jackson’s team found is considered brackish — containing low levels of salt — but it could be affordably desalinated, the study says.
“States such as Texas and Florida, and countries, including China and Australia, are already desalinating brackish water to meet their growing water demands,” the study says. “Accounting for deep but relatively fresh groundwater can substantially expand California’s groundwater resources, which is critical given the state’s current water shortages.”
Additional research is needed to determine how much tapping the water would cause the valley floor to sink and how oil and gas development, which is common in those deep aquifers, could contaminate the water, especially from fracking, according to the study.
“We're not advocating running out and drilling lots more groundwater wells,” Jackson said. “The Central Valley's been in denial about groundwater overdrafts for years. We need to consider ground subsidence. We also need to think about oil and gas activities directly in and around freshwater aquifers. Is that the best use of the resource long term?”
California’s water agency, the State Department of Water Resources, is concerned about the long-term implications of possibly using — and using up — a newly found reserve of freshwater.
“Understanding the total aquifer capacity is valuable from a technical standpoint, but a more useful estimate would be how much of the aquifer can we truly utilize before we experience significant impacts to surrounding agricultural, urban and domestic water users, to public infrastructures, to the environment and to the aquifers’ ability to recharge in a reasonable time frame,” said Lauren Hersh, spokeswoman for the California Department of Water Resources’ Sustainable Groundwater Management Program.
Leonard Konikow, an emeritus U.S. Geological Survey groundwater scientist and author of a 2013 federal government report on groundwater depletion in the U.S., said deep underground freshwater may be too expensive for many in California to access.
“In a severe drought, such deep drilling for water might be justified for municipal or industrial supplies, but I can’t imagine that the cost would ever be justified for agricultural purposes,” he said.
But Jackson said deep freshwater is a largely untapped and little-understood resource.
“It’s a huge pool of water,” Jackson said. “Some companies and towns are already pumping deep groundwater. It’s a little more expensive to use because of the pumping costs, but people are already doing it. Remember, too, that private landholders often have few restrictions on what they can pump.”