The water-rock interaction and anthropogenic contamination affecting to geochemical composition of shallow and deep groundwaters were investigated in the agricultural area of Myunggok-ri, Kongju. The shallow groundwater is classified into the chemical types of Ca-HCO₃and Ca-Cl(SO₄) and shows weak acid having an average pH 6.2. Deep groundwater shows the uncontaminated composition of the chemical types of Na-HCO₃and Na (Ca)-HCO₃with pH of 8.4∼8.8. The grouping approach of chemical data of waters shows the distinguished trend between water composition influenced anthrophogenic input and water composition mainly determined by natural process such as water-rock interaction. The main anthropogenic inputs affecting chemical composition of shallow groundwater are the contaminants such as K+, NO₃, Cl having average values of 4.4 ㎎/ℓ, 22 ㎎/ℓ, 13.7 ㎎/ℓ, respectively. The contaminants were probably derived from fertilizer, sweage, septic tank, and stable, etc. The hydrogen and oxygen isotopic compositions indicate that five deep groundwaters were recharged from different altitudes, and that shallow and deep groundwaters were originater from meteoric water. Tritium contents of waters suggest that deep groundwater. The results of this study may serve as a basic data for the future study of shallow grounewater as a drinking water in agricultural area, in Korea.
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