An Isotopic Geoindicator in the Hydrological Cycle

This paper synthesizes the research findings on the stable isotopes (δ2H and δ18O) of the water molecular, with respect to applications in tracing the natural water cycle. A general purpose diagram of δ2H versus δ18O 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 H2S, CO2, 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.