Aquifears

By Sylvia Wright

Groundwater is underfoot, underappreciated and under siege. After a half-century of overpumping and pollution, wells that once were expected to pour out pure water forever are now turning toxic and drying up.

Water is the planet's lifeblood," says UC Davis hydrogeologist Graham Fogg. "It nourishes life and removes waste. And while most people think our groundwater is OK, our work suggests otherwise.

Although most of our groundwater is still relatively clean, signs of trouble are showing up wherever humans pump aquifers. In agricultural areas, pesticides, fertilizers, salt and animal wastes are accumulating in the groundwater, and more water is being taken out of some aquifers than is put back in. In urban areas, groundwater is beginning to absorb the chemical residues of modern militarization, industrialization and scientific research.

The impacts are serious and widespread:

* The land has sunk as subsurface layers have compacted beneath the San Joaquin and Silicon valleys in California and beneath Houston, Mexico City and Beijing.

* Saltwater intrusion threatens aquifers in the Salinas Valley, in Los Angeles County and in Palestine's Gaza Strip.

* Contaminants threaten groundwater beneath thousands of toxic-waste sites in the United States, including one Superfund site on the UC Davis campus and another in the city of Davis. The agricultural pesticide DBCP, widely used between 1957 and 1977, has been found in thousands of wells in California's Central Valley; the gasoline additive MTBE has contaminated aquifers from Maine to Malibu.

* Ecosystems of rivers, lakes, marshes, estuaries and bays, which are fundamentally linked to groundwater, have been damaged by overpumping and contamination of aquifers. Pollutants in groundwater foul Chesapeake Bay; reduced stream flows have jeopardized the fall salmon run in the Central Valley's Cosumnes River.

"A burgeoning population, expanding industry and a large irrigated agricultural industry have stressed groundwater resources to levels not dreamed of just a generation ago," reports the California Department of Water Resources. Because of increased demand alone, "we are projecting an overall shortage of water by 2020," said the department's chief groundwater hydrologist, Carl Hauge. "Contamination could increase that shortage significantly."

At UC Davis, many scientists are trying to understand and preserve the planet's complex plumbing system. UC Davis has the greatest concentration of subsurface hydrologists of any university in the United States, with the possible exception of the University of Arizona. "We have tremendous strength in subsurface hydrology research and education," Fogg said. He and three other researchers concentrate on groundwater; five more concentrate on the vadose zone, between the water table and the land surface, and several others focus on the chemical or biological processes that affect contaminant transport. These scientists and engineers are based in the departments of Land, Air and Water Resources; Civil and Environmental Engineering; and Chemical Engineering and Materials Science; and collaborate with other researchers across the campus on related water issues.

"The research and outreach that UC Davis hydrologists are doing are absolutely critical," said UC Davis professor Richard Howitt, an expert in water economics. "This information will help users regard groundwater as a natural resource that should be looked after--and can be looked after for the first time because they understand it."

It's appropriate that UC Davis should be a leader in this field. The campus sits in the great Central Valley, where irrigated agriculture in a near-desert supplies half the nation's fruits, nuts, grains and vegetables. California water practices are infamous for their audacity and dissension, and serve as models for other dry regions. And UC Davis' formidable strengths in agricultural and environmental sciences, teamed with one of the nation's best geology departments, form a powerful basis for important studies of the complex basic and applied questions in the field.

Those interdisciplinary linkages are moving the science ahead, says another UC Davis groundwater hydrologist, Timothy Ginn. "UC Davis is unique in that not only are all the disciplines represented but also that we're collaborating. There are other places that have a similar spectrum of capabilities--but they don't work together."

Subsurface hydrologists like to joke that their jobs would be simple if water never went underground. One way Graham Fogg is trying to better understand the physics, chemistry and biology of this largely in-accessible realm is by developing unprecedented, three-dimensional computer models and simulations of groundwater behavior. This work has made it possible for the first time to predict in detail how vulnerable a particular aquifer is to contamination and where and how fast contaminants would travel. The innovations helped Davis researchers advise the California governor recently on MTBE contamination and on options for disposal of low-level nuclear waste. Now they are at the crux of a study Fogg is doing for the California Department of Health Services in Rancho Cordova.

Sometime before 1997, ammonium perchlorate, a chemical used to stabilize solid rocket fuel, leaked from an aerospace research facility near Rancho Cordova into drinking-water wells thousands of feet away. The toxicological effects of the chemical are currently being studied; scientists are concerned that perchlorate may impair the human thyroid gland's role in metabolism and development. Fogg and UC Davis associate researcher Michael Johnson are using the new models to help epidemiologists estimate how much perchlorate might have reached the people drinking from the contaminated wells.

These powerful new tools are built on a foundation of other UC Davis discoveries. One is Fogg's finding that the ages of the individual molecules in a single glass of well water can vary by tens or tens of thousands of years. One ounce might be "young," having percolated beneath the earth's surface since the 1950s, with the remaining seven ounces being pre-1950, pre-1800 or even prehistoric water. "This has profound implications for the sustainability of the resource," Fogg said. "It means that if we don't stop polluting, then future water samples from the same well will contain ever higher proportions of modern contaminated water."

Another key discovery has been the previously unappreciated influence of buried, ancient soils known as paleosols on groundwater movement and contaminant transport. Paleosols are widely found in California aquifer systems. One paleosol lies beneath Sacramento, in the Rancho Cordova perchlorate study area, and its exposure in the bed of the American River downstream of Sunrise Boulevard forms the San Juan Rapids.

Fogg's Ph.D. student Gary Weissmann, now an assistant professor at Michigan State, demonstrated that paleosols strongly inhibit the vertical movement of groundwater and contaminants. Similarly, Fogg and his postdoctoral researcher Eric LaBolle found that once contaminants diffuse into zones where groundwater moves ultra-slowly, such as paleosols, silt and clay, those contaminants tend to stay put. That means clean-up, or remediation, of contaminated groundwater often will be impossible or extremely expensive. Fogg and LaBolle, with another of Fogg's past graduate students, Steve Carle, have developed the first models capable of realistic simulations of these phenomena.

The work done by Fogg and his students required that they map the subsurface in detail. Timothy Ginn focuses on how to predict contamination arrival at a water well when such detailed information isn't available. He is building a model that integrates all the possible chemical, physical and microbiological phenomena that affect contaminant travel. His two main tools are streamtubes and memory. Streamtubes are the pathways through the gravel beds of an aquifer. Memory is a characteristic of some chemical reactions; the rate of the reaction is influenced by how long the agent has been at the reaction site. For example, when certain groundwater contaminants diffuse into a paleosol, they stick to the grains of the paleosol. The rate at which they come unstuck depends on how long they've been stuck. Ginn is collaborating with Tom Young, assistant professsor of civil and environmental engineering, on models that take into account both these memory effects and transport in streamtubes.

Ginn, an associate professor of civil and environmental engineering, came to UC Davisin 1997 from the Department of Energy's Pacific Northwest National Laboratory. Pacific Northwest helps the Department of Energy clean up aquifers underlying nuclear-weapons production sites, which are some of the most contaminated sites in the world. One of these sites, the infamous Hanford atomic-weapons reservation adjacent to the Pacific Northwest lab, is the most contaminated subsurface site in the United States. Ginn can rattle off every category of groundwater contaminant known to science--and it's a long list. There are agrichemical agents such as pesticides, fungicides and fertilizers; industrial agents such as trichloroethylene (TCE), a solvent contaminating more than half the Superfund sites; heavy metals such as cadmium, lead, nickel and arsenic from industrial processing, weapons production and mining operations; radioactive wastes such as isotopes of the elements uranium, cesium and strontium from nuclear-weapons research and production; naturally occurring inorganic mineral salts; nutrients such as nitrates and phosphates from fertilizers; and microbiological agents from livestock wastes, such as bacteria, viruses and protozoans.

Ginn is pretty sure he won't run out of work. "I went into this field 20 years ago because I was interested in cleaning up groundwater," he said. "Often in the sciences, the research questions change. This hasn't. It's gotten worse and worse and worse. There's more groundwater to be cleaned up, the problems are continuing to grow, and the supplies are continuing to diminish."

Another UC Davis faculty member, Miguel Mariño, is known worldwide among hydrologists for his expertise in groundwater contamination by agricultural pesticides and nutrients. Mariño is a professor of hydrologic sciences, civil and environmental engineering, and biological and agricultural engineering. He and a former student, Mohamed Hantush, developed a model named RISK that is widely used by water regulators and managers to predict the expected effects of various pesticides in both groundwater and surface water. The RISK model is used to maintain aquifers under corn and soybeans in Maryland, sugar cane in Australia and golf courses in Spain. Mariño also uses models to address problems of groundwater recharge and sustainability. As his colleagues have shown, much of the water underground is "fossil water" that took a long time to accumulate. Once pumped out, it isn't easily put back.

In a recent project funded by the UC Water Resources Center, Mariño and past students Keith Larson and Hakan Basagaoglu analyzed historical irrigation practices to study land subsidence in the Los Baños-Kettleman City area. He found the ground had already sunk as much as 28 feet during 1926-1972 and predicted future subsidence based on various growth scenarios.

"A lot of folks at the state and federal levels are very interested in these questions.What areas can you pump the most from and which should you stay away from?" Mariño said. "If present practices could be sustained for 30 years for the Los Baños-Kettleman City area, land subsidence would not be a serious problem. However, with the continued growth of urban populations to the south and ecological concerns about water exportation from the north, those practices may not be sustainable."

Teaching water users about all these findings is hydrologist Thomas Harter, an associate UC Cooperative Extension specialist. Harter is the only groundwater extension specialist in California and one of a few in the country. He spends about half his time teaching people outside the university what is known about groundwater and how they can put that knowledge to work to protect the resource and save themselves money. His students include water managers, public planners, policy makers, growers, ranchers and agricultural consultants.

"Thomas' contributions to public education are huge, because when people try to manage groundwater or to legislate policy, the outcomes are dominated by misconceptions," said Graham Fogg, who often teaches in Harter's workshops. "We'll never get past that until more people are educated on the fundamentals of groundwater." Said Harter, "My students are people in the real world struggling to understand groundwater issues. I have seen the help I can give, and it is great to see how it helps people make better decisions."

For the past five years, Harter has been based at UC's Kearney Agricultural Center, just south of Fresno. Last fall, in response to rising requests for his expertise at the state capital, he moved his main office to the Davis campus. He will continue his outreach in the Central Valley.

Harter also has a very active research program. One project is a study of whether dairy operations have a significant impact on groundwater quality. It's an important question in California, where 1.4 million cows produce most of the nation's milk--and about 60 billion pounds of liquid and solid manure annually.

Dairies typically deal with all that waste by spreading it as fertilizer over the fields where they raise forage crops for the cows. But it hasn't been clear whether all the constituents of the manure, some of which can make people sick, are taken up by the growing crops or else filtered out in the soil. If not, they could be seeping into aquifers. A key constituent of manure that Harter is tracking is nitrogen, which turns to nitrate in groundwater. When consumed at high levels in drinking water, nitrate can interfere with oxygen transport in babies and lead to "blue-baby syndrome." To find out if high levels of nitrate are traveling from dairies to drinking water, Harter has built a network of 79 wells on five cooperating dairies in the San Joaquin Valley; it may be the most densely monitored dairy system in the nation.

So far, Harter has closely examined groundwater to a depth of only about 25 feet, in an area where drinking water is taken from 50 feet or deeper. His preliminary results show "there is quite a bit of nitrate reaching that shallowmost groundwater from these dairies due to overapplication of manure to some of their fields," he said.

Harter, Cooperative Extension farm advisors and specialists and the dairy owners are testing safer methods of manure recycling in barns, corrals, storage ponds and fields. Harter's 79 wells will show if those methods are effective and, if so, which work best. "The next question is, how do we integrate the groundwater impacts from all these strategies over a whole dairy, and then over a dairy region--a 'milkshed'?" he said. "That's where it all gets interesting."

Harter is also working with Graham Fogg and Timothy Ginn to make the group's complex models useful outside the research community, to Harter's people in the real world. Said Fogg, "Today we are building models with millions of bytes of information.One day we hope to have smarter mathematics that will allow us to do the analyses more simply--perhaps even without a computer, or with just a calculator."

At this time last year, California was so dry that some people were fearing drought--a phenomenon that doubles the amount of water that users pump from the state's aquifers. That crisis was averted when a series of wet storms finally rolled through in January. But drought is a normal part of California's long-term weather pattern, and dry times will surely come again. When they do, the precarious state of our groundwater supplies will become evident to more people than just the hydroscenti. Water officials and consumers may finally talk seriously about groundwater conservation and resource management--the keys to clean, abundant supplies.

"The best thing to do when it comes to keeping groundwater safe is prevention," Mariño said. "It takes a lot of time and money to clean up an aquifer. And sometimes you can't clean it up." Fogg agreed. "We need to hedge our bets toward protecting the resource, not toward remediation. Ground-water stewardship needs to be practiced at the city, state, farmer and industry levels. Our research should help that stewardship move out across the entire landscape."

For more information:

MAGAZINE ARTICLES

• "Running Dry," by Jacques Leslie, Harper's Magazine, July 2000
• "When the World's Wells Run Dry," by Sandra Postel, World Watch, September/October 1999

BOOKS

• Water: The Fate of Our Most Precious Resource, by Marq de Villiers; Houghton Mifflin, 2000
• Life's Matrix, by Phillip Ball; Straus & Giroux, 2000
• Cadillac Desert: The American West and Its Disappearing Water, by Marc Reisner; Penguin Group, revised 1993
• Assembling California, by John McPhee; Noonday Press, 1993

INTERNET SITES

• UC Davis Groundwater Web page: www.uckac.edu/groundwater/gwindex.htm
• UC Cooperative Extension Groundwater Program: www.uckac.edu/groundwater
• The Groundwater Foundation: www.groundwater.org/
• U.S. Environmental Protection Agency Groundwater Primer: www.epa.gov/seahome/groundwater/src/ground.htm#toc
• U.S. Environmental Protection Agency Superfund program: www.epa.gov/superfund
• U.S. Water News Online: www.uswaternews.com/homepage.htm

GUIDES AND POSTERS

• Water Education Foundation, Sacramento, Calif.; phone: (916) 444-6240; online: www.water-ed.org
• California Department of Water Resources: well.water.ca.gov/gwbrochure/