EAST SAN JOAQUIN WATER QUALITY FRAMEWORK: EFFECTS OF URBANIZATION ON WATER QUALITY

摘要

Historical and recent surface water quality data measured in the East San Joaquin Water QualityrnFramework region indicate that a number of parameters, including pesticides, nutrients, andrninorganics, have been detected, sometimes at concentrations that exceed regulatory water qualityrnobjectives or other nonregulatory screening thresholds. Because much of the land use in thernregion is agricultural, it is often assumed that agriculture is the primary source of water qualityrnpollutants. Although the contributions of nonagricultural sources such as urban, residential, andrnindustrial sources have not been well quantified, in some cases they may account for a significantrnportion of the pollutant load. For examples, two of the inorganics most frequently found atrnelevated concentrations are copper and zinc, which may occur in urban and highway runoff duernto brake pad and tire wear. In addition, many of the pesticides detected in surface water in thernregion are used for both nonagricultural and agricultural purposes. In some cases, residential usernis estimated to account for up to half the use of certain pesticides. One of the objectives of thernwork conducted under the Framework is to provide information to help differentiate betweenrnurban and agricultural sources, using data on pesticide use, land use, and spatial and temporalrntrends in water quality data. This knowledge will be useful in formulating management practicesrnto help reduce pollutant loads to surface water bodies in the region.