Geohydrologic interpretations of a volcanic island from environmental isotopes

Abstract

Isotopic analyses of ground waters collected from 1966 through 1968 on Cheju Island, Republic of Korea, have proved helpful in interpreting the general hydrologic relations and in developing a model of the ground‐water flow system in the permeable volcanic rocks of the island. Comparison of tritium and stable isotope (D‐ 18 O) contents provided a basis for a model of the ground‐water flow regimes. Time variability of these isotopes determined by repeated samplings provided the basis for estimates of mean residence time of ground waters, ranging from about 2 to 9 years. Although the results are only approximate because simplified models were used, they can be of substantial assistance in planning further hydrologic investigations and appraising the feasibility of ground‐water development.