UC Toxics News: Spring 2001
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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 life blood," 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:

  "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 in making 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 doctoral 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.