ASSESSING GROUNDWATER NITRATE CONTAMINATION FOR RESOURCE AND LANDSCAPE MANAGEMENT

Groundwater nitrate concentrations increased and sometimes exceeded pu blic health standards during the last 50 years in Tulare County, Calif ornia, where ecological health and agricultural productivity are at ri sk. This study explained same of the spatial variation in groundwater nitrate concentration by spatial coincidence of soil leaching potentia l, agricultural land uses, and the groundwater elevation. Groundwater nitrate concentration increased where excess nitrogen loads in soils w ere greatest, soils rated highest for leaching potential, and groundwa ter elevation was higher. The high-risk nitrate leaching and contamina tion sites were most prevalent on townships where citrus, nut orchards , and vineyard crops were grown on coarse-textured soils, The assessme nt made use of available data at a spatial scale appropriate for devis ing management solutions, and the maps communicated the information ef fectively. Farmers and planners can use this information to adjust far m-management practices and landuse strategies to minimize nitrate cont amination risks in groundwater.