Tracing of water movement in the unsaturated zone using stable isotopes of hydrogen and oxygen

The development of an analytical model for movement of the stable isotopic species of water in unsaturated soils is presented by means of a review of recent literature on the subject. The model adequately represents experimental observations of isotope profiles during evaporation from saturated or unsaturated soils, under both nonisothermal and nonsteady conditions. Interpretation of field isotope profiles using the model is discussed, and indications are made of areas where further work is desirable.