California groundwater degradation: Agricultural practices and management strategies
1998
Marino, M.A. (University of California Davis (USA). Dept. of Land, Air and Water Resources and Dept. of Civil and Environmental Engineering)
California's groundwater resources, which provide from 40 to 60 percent of the State's water supply, are threatened by excessive exploitation and chemical contamination. One of the principal concerns about groundwater contamination involves potential risks to human health. Agricultural practices are the largest nonpoint source of groundwater contamination in California. Three-quarters of the groundwater supply in the State that is already impaired by pollution have been degraded by salts, nitrates, and pesticides primarily from agricultural practices. Management strategies are discussed by which problems associated with saline drainage water, nitrates and pesticides can be controlled. Salinity concerns in groundwater are primarily economic. Crop yields decrease as salt in the irrigation water increases beyond the optimal ranges specific to individual crops. Salinity is a significant problem for much of California's irrigated agriculture. The occurrence of nitrate in groundwater is important because of its potential health effects. Perhaps, the biggest problem with nitrates is the treatment cost associated with their removal. Approximately 1,000 public wells have been closed in California due to high nitrate concentrations. Pesticide detection occur most frequently in California's Central Valley, a region of intensive farming. Irrigation water management plays a major role in the transport of pesticides. A physically based analytical model suitable for long-term predictions of pesticide concentrations in groundwater is discussed. Atrazine is selected to illustrate the capability of the model.
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