Vulnerability of Shallow Aquifers of the conterminous United States to Nitrate: Assessment of methodologies
Abstract (Summary)Groundwater is an important natural resource for numerous human activities, accounting for more than 50% of the total water used in the United States. Groundwater is vulnerable to contamination by several organic and inorganic pollutants such as nitrate, heavy metals, and pesticides. Assessment of groundwater vulnerability aids in the management and protection of limited groundwater resources. The focus of this thesis is to (1) statistically compare two groundwater vulnerability assessment models; modified DRASTIC (Acronym for Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, and hydraulic Conductivity of aquifer) and ordinal logistic regression for NO3- contamination of shallow groundwater of the US, (2) analyze any discrepancies in the predictability of each of these models, and (3) discuss the advantage of each of the above-mentioned models with respect to performance, data requirement, and its ability to predict vulnerability. Analysis of NO3- concentration in groundwater allows for a reliable comparison of the two models. The results from the OLR model indicate a better correlation between the observed and average predicted probabilities. A very low R2 value was obtained between the modified DRASTIC and nitrate concentration, indicating poor prediction capabilities and need for high resolution data. Limitation with respect to requirement of more data with respect to prediction is seen in both the methods.
School:Utah State University
School Location:USA - Utah
Source Type:Master's Thesis
Date of Publication:12/01/2008