An Isotopic Geoindicator in the Hydrological Cycle

Abstract This paper synthesizes the research findings on the stable isotopes (δ 2 H and δ 18 O) of the water molecular, with respect to applications in tracing the natural water cycle. A general purpose diagram of δ 2 H versus δ 18 O may serve as a geo-indicator of various circulation processes the water is involved: hydrological, hydro-meteorological and hydro-geochemical. Equations and explanations are provided for a total of 13 lines in the diagram that are illustrated to show the fractionation and changes of stable isotopes when experiencing different processes: GMWL; Moisture recycling line; evaporation line, mixing lines with seawater and andesitic water, exchange lines with H 2 S, CO 2 , silicate mineral, hydrocarbon, carbonate and clay minerals. These lines serve as a basis in using water stable isotopes in the hydrological, hydrogeological and paleo-climate research.