Abstract

A case study of the application of geostatistics to define the spatial distribution of nitrate in groundwater at a 12-acre test site in southern Idaho is presented. Results also are presented for a spatial map subtraction technique used to evaluate the effectiveness of a U.S. Department of Agriculture recommended nutrient Best Management Practice (BMP) for the test site. Nitrate concentration data for 35 point groundwater samplers situated in the shallow, unconfined aquifer at the test site were used in this evaluation. One hundred conditional, sequential Gaussian simulations were generated to produce expected-value estimate maps of nitrate concentration distributions for the first 3 months of implementation of the nutrient BMP. Net difference maps calculated from these E-type maps were used to evaluate nitrate changes at the site. Results of this evaluation suggest that the BMP has a statistically significant influence on the influx of nitrate to groundwater at the site.