ENVIRONMENTAL-IMPACT EVALUATION OF SPATIAL MANAGEMENT-PRACTICES USINGSIMULATIONS WITH SPATIAL DATA

This paper addresses the diffuse [non-point source (NPS)] contaminatio n problem by integrating the environmental impact analysis in producti on practices with the economics of spatial management methods. It empl oys a combination of geostatistical simulation and unsaturated zone tr ansport modeling to evaluate the effect of spatial variability of soil -related parameters on NPS ground water contamination. Five management scenarios of spatially variable nutrient application are developed an d evaluated on the basis of their impact on production agriculture and possible environmental pollution. The scenarios are evaluated conside ring the spatial variability of residual soil nitrate, yield, and hydr aulic conductivity in the field. The process is applied to three reali stic cases, differing in the extent of spatial variability, ranging fr om low to high variability. The modeling results indicate that the ide ntified framework holds promise for evaluating spatial management prac tices in terms of production as well as protection of the environment. For example, results indicate that variable application of nutrient, based on spatially variable parameters, not only reduced the overappli cation but also reduced the overall ground water contamination potenti al. However, the results suggest that the spatial management system ma y not necessarily result in a decrease in contamination loading for so me fields, particularly those which exhibit a low variability of selec ted parameters. Furthermore, results indicate the presence of a break- even point between the benefits of spatial management technology and t he efforts used in implementing this technology for various degrees of spatial variability. Beyond this point, the excess efforts appear to result in relatively small marginal benefits.