Geostatistical techniques to evaluate groundwater contamination and its sources in Miryang City, Korea

Miryang City has high seasonal variations in precipitation and small number of surface reservoirs. It uses much groundwater for living and irrigation purposes. This study delineates the characteristics and the controlling factors of groundwater contamination using multivariate statistical analyses and kriging method. GIS spatial maps showed that groundwater contamination was occurred mainly in the central and southern areas and partly in the southwestern and northern areas. It may be attributed to the effect of residual saline water, irrigation, livestock wastes and municipal sewage. Ca-HCO₃ water type was the most predominant in the groundwater of the study area. Ca-Cl₂, Na-Cl and Na-HCO₃ water types were dominant in order, due to the influence of residual saline water and anthropogenic activity. Geostatistical techniques were applied to classify the groundwater samples and to identify the geochemical processes and sources controlling the groundwater geochemistry. The scatter diagrams of factor score versus topographic elevation and groundwater level represented that groundwater was influenced by saline water and NO₃-N at <85 m of well elevation. The areas and degrees of groundwater contamination were understood from the spatial distribution maps of factor scores versus groundwater level. Chemical characteristics and contamination sources of groundwater were identified from cluster and factor analyses. Kriging method was useful for the production of distribution maps showing the degree and location of groundwater contamination. Thus, geostatistical techniques including factor analysis, cluster analysis and kriging method played very important roles in evaluating groundwater contamination and identifying contamination sources.