Colloquium presentation jointly hosted by Graduate Program of Hydrologic Sciences, Department of Civil and Environmental Engineering, and Environmental Science Graduate Program. Social will follow in foyer outside auditorium.
A significant fraction of U.S. agricultural regions suffers from poor drinking water quality due to elevated groundwater nitrate, particularly in private domestic and local small system wells. Using extensive data collection and developing innovative modeling tools, we identify sources and reduction/prevention options for nitrate in groundwater used as drinking water, assess current groundwater quality, simulate historic and future dynamics of groundwater nitrate at high resolution across large groundwater basins, develop recommendations for groundwater cleanup programs, identify methods and costs associated with treatment of or alternative supply to nitrate contaminated drinking water, and identify potential funding sources. We selected one of the country’s most productive agricultural regions as a pilot area: the Tulare Lake Basin and Salinas Valley, home to 2.6 million people, nearly half of California’s 9 million acres of irrigated agricultural land, to more than 80 different crops, and to more than half of California’s nearly 2 million head dairy herd. Our work explores many interdisciplinary issues. In this presentation I will focus on our data analysis and modeling development efforts to characterize source loading and the transport of nitrate in the subsurface. In the study area, shallow groundwater nitrate contamination is widespread, with a statistically significant upward trend in the most affected region. Results highlight the longevity of groundwater contamination and the complexity of regulating an industry with tens of thousands of individual land owners growing hundreds of different crops. Treatment and alternative water supply options for safe drinking water are therefore developed and shown to depend on current service areas of public water supply systems. Alternative water supply options include bottled water, surface water, regionalization of public water supply systems, particularly smaller systems, new well drilling, and others. More information is available at: http://groundwaternitrate.ucdavis.edu.