Date of Graduation
Master of Science in Environmental Management (MSEM)
College of Arts and Sciences
Groundwater is an integral piece of California’s groundwater resources. One of the most common contaminants present in groundwater is nitrate. Nitrate contamination is often a result of agricultural land use activities on the ground surface. The study area for this analysis is the Salinas Valley Groundwater Basin, an agriculturally dominated basin in coastal California. The Salinas Valley Basin is both one of the most agriculturally productive areas of the state, as well as one of the most nitrate-contaminated basins in the state. The purpose of this research was to develop a groundwater vulnerability map for nitrate pollution in the Salinas Valley. A groundwater vulnerability assessment was carried out using a modified DRASTIC model. DRASTIC is a U.S. EPA rank-sum model for assessing groundwater vulnerability that incorporates depth to water, net recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity. In order to modify the DRASTIC model to assess nitrate contamination specifically, a land use parameter was incorporated into the model. The results of this assessment found 2.9% of the Basin has very low vulnerability, 50.6% has low vulnerability, 42.9% has moderate vulnerability, and 3.6% has high vulnerability. The results of the groundwater vulnerability assessment could not be validated using measured nitrate concentrations in the Basin. Four possible reasons for the poor fit of this assessment have been identified: (1) the temporal variability of select DRASTIC parameters, (2) the inability of the land use parameter to accurately represent nitrate vulnerability, (3) the high spatial variable of nitrate contamination in the Basin, and (4) the static weights assigned to parameters by the DRASTIC model.
Boyle, Bernadette, "Groundwater vulnerability assessment for nitrate pollution in the Salinas Valley using a modified DRASTIC model" (2017). Master's Projects and Capstones. 561.