Isotopic evolution of snowmelt and its hydrometeorological importance in snow-covered regions

Snowmelt, a component of the hydrological cycle, is influenced by changing climate and meteorological events. In the context of hydrometeorological studies, the water isotopic composition of snowmelt has been commonly used. This study examined temporal variations in the isotopic composition of snowmelt from an isotopically heterogeneous snowpack to the context of accurate quantification of isotope-based hydrograph separation. In this study, a one-dimensional model was used to simulate the isotopic variations of the meltwater by varying the initial isotopic compositions of the snow layers and parameters such as effectiveness of exchange (ψ), ice-to-liquid ratio of the exchange system (f), and water saturation (S). Isotopic evolution is sensitive to the initial layer sequence of isotopically enriched or depleted snow in the snowpack and the extent of isotopic differences between the layers. More variated patterns are observed in the isotopic evolution as the ψ and f values are increased; particularly, a significant modification is observed in the bottom layer that is altered by the enriched top layer, thereby further affecting the pattern of isotopic evolution. The isotopic heterogeneity has been suggested to be a significant factor in the isotopic evolution of snowmelt, even though various other influencing factors have been considered under natural conditions. Because of the close dependence of snow and glacial conditions upon climate change, this study is expected to support further hydrometeorological studies, particularly in snow-dominated regions.