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 Quality Framework region indicate that a number of parameters, including pesticides, nutrients, and inorganics, have been detected, sometimes at concentrations that exceed regulatory water quality objectives or other nonregulatory screening thresholds. Because much of the land use in the region is agricultural, it is often assumed that agriculture is the primary source of water quality pollutants. Although the contributions of nonagricultural sources such as urban, residential, and industrial sources have not been well quantified, in some cases they may account for a significant portion of the pollutant load. For examples, two of the inorganics most frequently found at elevated concentrations are copper and zinc, which may occur in urban and highway runoff due to brake pad and tire wear. In addition, many of the pesticides detected in surface water in the region are used for both nonagricultural and agricultural purposes. In some cases, residential use is estimated to account for up to half the use of certain pesticides. One of the objectives of the work conducted under the Framework is to provide information to help differentiate between urban and agricultural sources, using data on pesticide use, land use, and spatial and temporal trends in water quality data. This knowledge will be useful in formulating management practices to help reduce pollutant loads to surface water bodies in the region.