REGIONAL ESTIMATION OF GROUND-WATER VULNERABILITY TO NONPOINT SOURCESOF AGRICULTURAL CHEMICALS

The potential for ground water contamination by, agricultural chemical s exists in many regions of the world. A collaborative effort between Hungarian and United States scientists has developed a general strateg y to estimate the regional vulnerability of ground water to agricultur al chemicals. The midwest U.S. and most of Hungary are major agricultu ral regions with similar hydrogeologic settings. Many areas where grou nd water provides public drinking water supplies in these regions are vulnerable to ground-water contamination. The vulnerability of shallow , unconsolidated aquifers and thinly-covered bedrock aquifers to agric ultural chemicals is being investigated in an initial application of t he strategy. This strategy integrates elements of overlay methods of v ulnerability estimation, process-based modeling methods, and statistic al methods. Strategy steps include: identifying characteristics of gro und water needed to classify regional ground water resources; mapping the spatial distribution of aquifer classes (unconsolidated and bedroc k) using a regional geographic information system; and estimating the occurrence of agricultural contaminants by applying leaching models to representative conditions in each aquifer class. In the U.S. project, pedologic data bases are being used for both mapping aquifer classes and model input. Estimated vulnerability will be evaluated against dat a from a regional survey of shallow aquifers recently completed in the Midwest. The Hungarian project is developing new maps of basic hydrog eologic characteristics with data that can be used to model vulnerabil ity of the I-meter root zone, the unsaturated zone, and the saturated zone. Published by Elsevier Science Ltd.