SUSCEPTIBILITY OF SURFACE WATER IN TEXAS TO NONPOINT SOURCE PESTICIDECONTAMINATION

摘要

Surface-water (streams and reservoirs) sources of public drinking-water supply (PWS) are susceptible tocontamination from point and nonpoint sources. The Texas Commission on Environmental Quality (TCEQ) and the U.S.Geological Survey (USGS) developed a system for assessing the susceptibility of PWS source waters to the occurrence of227 contaminants. To accomplish these assessments for surface-water PWS’s, water-quality data at 323 USGS and TCEQsampling sites are matched with GIS-derived basin characteristics data for the watersheds upstream from these sites. Logisticregression models are then used to estimate the probability that a particular contaminant will occur above a given thresholdconcentration. Once developed, these equations are used to estimate the probability of contaminant occurrence at PWS’s. Formany of the 227 contaminants, either monitoring data or contaminant detections were insufficient to produce viable logisticregression models. Significant models were developed for 20 (32%) of the 64 contaminants classified as pesticides.