Use of Geographic Information System in Analyzing Effects of Land Use on Ground-Water Quality, San Joaquin-Tulare Basins, California

Jo Ann M. Gronberg, and Donna L. Knifong

In:
Marston, R.A., and Hasfurther, V.R., eds., 1994, Proceedings -- Effects of human-induced changes on hydrologic systems: American Water Resources Association, 1994 Annual Summer Symposium, Jackson Hole, Wyoming, June 26-29, 1994, Poster, p. 103.

Abstract:
A Geographic Information System (GIS) is being used to facilitate selection of appropriate wells in vinyard areas for shallow ground-water sampling in an effort to analyze effects of land use on ground-water quality in the San Joaquin-Tulare Basins, California. This study is part of the National WAter Quality Assessment Program of the U.S. Geological Survey. Using GIS, the total number of shallow wells originally retrieved from the U.S. Geological Survey Ground Water Site Inventory data base for the study area was reduced fron 1,931 domestic and test wells to 131 wells located in vineyards. The number of shallow acreage in a 0.5-mile radius was greater than 50 percent fo the land use. Vineyard areas were selected from a detailed digital map of agricultural land use compiled from a California Department of Water Resources county-level survey. The total acreage of vineyards was restricted to 516,013 acres of vineyards cultivated on alluvial-fan deposits in eastern San Joaquin Valley. This acreage was divided in 20 equal-area cells. The 92 wells were randomly selected to ensure that each cell is represented. The network selected using the GIS will be refined by field canvassing to confirm the selection of approproate wells for shallow ground-water sampling.