Hydrogen and oxygen isotopic compositions of subsurface water at Bajawa area, central Flores, Indonesia

Abstract

Samples of spring and stream water, and rainfall were obtained within 50 km of Bajawa City, central part of Flores Island, eastern Indonesia. Hydrogen and oxygen isotopic compositions of the samples were analyzed. (1) On the relation diagram between hydrogen and oxygen isotopic compositions, water samples were plotted near the meteoric water line. The sample d-values taken in 1998 and 1999 were about 10 and 20, respectively. The change of d-value may reflect the isotopic difference of rainfall in winter and summer. (2) Altitude (topographical) effects for hydrogen and oxygen isotopic compositions of subsurface water in this area were -0.98‰/100m for hydrogen isotopic composition and -0.13‰/100m for oxygen isotopic composition, which were within the range of those found for other islands.