Date of Award

4-1-2023

Degree Name

Master of Science

Department

Geography

First Advisor

Adam J. Mathews, Ph.D.

Second Advisor

Lisa M. DeChano-Cook, Ph.D.

Third Advisor

Chansheng He, Ph.D.

Keywords

Groundwater, Madinah area, nitrate, Saudi Arabia

Access Setting

Masters Thesis-Open Access

Abstract

High levels of nitrate in groundwater are a serious problem in Madinah Area, Saudi Arabia. Identifying factors affecting groundwater nitrate contamination is important for managing groundwater quality. This study examined factors that have significant impacts on the high level of groundwater nitrate in Madinah Area. Factors examined included well-depth and land cover. Relationships between variables were explored using three statistical approaches: the Kruskal-Wallis test and two types of regression (ordinary least squares [OLS] and geographically weighted regression [GWR]).

Nitrate concentration data show that 73% of obtained groundwater samples exceeded the United States Environmental Protection Agency (EPA) maximum contaminant level (MCL) of 10 mg/L in Madinah Area. Results indicate that well-depth and agricultural lands have negative significant impact on groundwater nitrate concentrations. Based on the adjusted R2, OLS and GWR models explain 38% and 37% respectively, of the nitrate concentration on groundwater. GWR model shows better performance compared to the OLS model by having higher R2 and lower Akaike Information Criterion (AIC) value.

This study suggests that there could be sources of contamination on the land surface of Madinah Area, other than built-up and agricultural lands. Since nitrate concentration in groundwater did not increase as the percentage of built-up and agricultural lands increased, as has been found in other studies. This suggestion is supported by the inverse relationship between the concentration of nitrate in groundwater and well-depth.

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