Pesticide Leaching Analytical Model and GIS-Based Application in Agricultural Watersheds

Ground-water contamination by pesticides and other organic pollutants has been detected across agricultural areas and is on the increase. Because ground-water monitoring is too costly to define the geographic extent of contamination at such large scales, indirect methods are needed to predict transport and fate of pesticides in the subsurface and assess the potential for ground-water contamination that may result from applications of pesticides. In this paper, two analytical solutions that describe one-dimensional transport and fate of pesticides in the soil, were integrated with a geographic information system (GIS) to estimate spatial solute leaching distributions and to create ground-water vulnerability assessment maps. The GIS-based models use process-based equations that consider advection and complete mixing to simulate solute transport and to predict pesticide transport in both space and time. To demonstrate its capabilities, the modeling approach is applied to an agricultural watershed in the mid-Atlantic coastal plain using data from county soil survey and monitoring study in this region. The impact of processes, such as net infiltration, biochemical degradation, adsorption and advection on the spatial and temporal distribution of pollutant emissions to ground water are investigated. The applicability of GIS-based models for vulnerability assessment and determining the risk of ground-water contamination by pesticides is demonstrated in susceptible agricultural areas.