Study on Hydrological Processes in Lena River Basin using Stable Isotope Ratios of River Water

Lena river water was sampled at Yakutsk and its isotope ratios were observed. The isotopic composition of river water showed a clear seasonality, with a pulse of low δ values due to runoff of snow meltwater, and following an increase in δvalues during summer, which may be caused by a recession of snow meltwater and runoff originating from summer precipitation with more positive δ values. The isotope ratios of river water slightly decreased again during the freezing period, when there was low discharge. As the freezing process of the ground progresses from the surface down, the soil layers producing runoff may become deeper. This may cause the gradual decrease in δ values observed in winter. It has been pointed out that winter discharge showed an increasing trend in eastern Siberia. An increasing trend is most obvious in the area covered by permafrost. Monitoring of isotope ratios of river water may improve our understanding of the source and process of increasing winter discharge. (author)