[en] The application of environmental isotope as a tracer in water resources studies is presented. The main objectives of this paper are to investigate the distribution and origin of water resources involved in the study. Isotope technique is a useful tool in determining the groundwater recharge sources, ages of water bodies, interaction between surface water and groundwater, source of groundwater contamination, degree of mixing and for estimating subsurface residence time. The environmental isotopes, particularly stables isotopes of water (¹⁸O and ²H) are measured using Continuous Flow Isotope Ratio Mass Spectrometer (CF-IRMS). Oxygen and hydrogen isotope compositions are reported as delta (δ) and denoted as % or per mill, a variation which is relative to a known standard (Vienna Standard Mean Ocean Water, VSMOW). This study has successfully demonstrated the ability of isotope technique in delineating the water resources. The findings that are obtained from this study would greatly assist local water authorities or related agencies to manage their water resources for the socio-economic benefit of the region. (author)