Nitrate Sources, Groundwater Quality, and Drinking Water in the Tulare Lake Basin

The Tulare Lake Basin is located in the southern half of the California Central Valley. It hosts nearly 4 million acres of irrigated farmland. It is one of the most diverse and most intensively farmed regions in the country with over 80 crops grown. It is also home to 2.3 million people that almost exclusively depend on groundwater as drinking water. Groundwater nitrate pollution is widespread. Many small communities are economically disadvantaged and have been unable to provide safe drinking water. A nitrogen loading assessment is conducted and loading reduction options in agriculture are developed and evaluated through literature review and expert panels. Potential economic costs of reducing agricultural nitrate leaching are assessed. Groundwater nitrate pollution is assessed in two tracks:  a comprehensive compilation of past and current groundwater nitrate data from private and public, local, regional, state, and federal resources is performed to assess current nitrate levels and historic trends; and an explicit regional linkage between nitrogen loading and historic and current groundwater nitrate is established by implementing a groundwater modeling study that tracks nitrate loading from the source to supply wells. Results support an assessment of treatment and alternative water supply options. Treatment options are compiled and treatment cost estimates developed. Factors affecting treatment selection and costs are examined including the influence of local water quality and co-contaminants. Alternative water supply options include bottled water, surface water, regionalization of public water supply systems, particularly smaller systems, new well drilling, and others. Costs, design factors, and conditions under which either of these options are feasible, are reviewed to provide guidance to rural communities facing nitrate contamination. Regulatory control of sources and funding options for providing safe drinking water are reviewed, alternatives developed and evaluated in a broad qualitative context that provides support to stakeholders and decision makers. http://www.waterboards.ca.gov/water_issues/programs/nitrate_project/index.shtml