Environmental Hazards Assessment Program Summary of Results for a Study to Identify Areas of Ground Water Contamination by Pesticides in California. SCOPE OF THIS MEMORANDUM

Having the ability to identify areas of land that are vulnerable to ground water contamination should facilitate the development of management and regulatory options that may be used on a regional scale. The prevalent approach to modelling land areas has been to identify contamination processes deductively and then construct theoretical models comprised of pertinent variables. Most models for pesticide contamination of ground water combine climatic, hydrogeologic, and/or soil variables in a manner that maximize discrimination in leaching potential between land areas, Furthermore, only simple percolation from the land surface is usually considered, movement in preferential flow paths is not described (National Research Council, 1993). In a recent conference on application of Geographic Information Systems technology to nonpoint source pollution problems, most reports identified areas vulnerable to simple-percolation leaching (Corwin and Wagenet, 1995).