The role of snowmelt discharge to runoff of an alpine watershed: Evidence from water stable isotopes.

• The maximum contribution ratio of snowmelt water to runoff was 59.8% higher than inland mountainous areas in Erdaobaihe River Watershed. • The response of water supply to climate change in semi-humid areas was very significant. • Snowmelt waterwill affect the balance of local water resources under the scenarios of global warming. Snow is an important form of water storage which profoundly affects the hydrological processes in alpine watersheds, especially the runoff during snowmelt period. As the strong impact of climate change, the concern about snowmelt water to runoff in alpine watersheds is dramatically growing. However, the studies are mainly focused on arid and semi-arid areas, the research on semi-humid regions sensitive to the climate change need to be strengthened. In this study, for evaluating the contribution of snowmelt water to runoff in snowmelt period, we calculated the stable isotope values (δD, δ18O and d -excess) of different water bodies including river, snow, rain, groundwater, and snowmelt water in the Erdaobaihe River watershed of Changbai Mountains area. The results indicated that the δ18O values of snowmelt water showed an increasing trend with increasing temperature, while the d-excess values of snowmelt water showed a decreasing trend. During the snowmelt period, the snow cover ratio varied from 20.31% to 0.02%. The contribution ratio of snowmelt water to runoff was from 14.4% to 59.8% with average of 42.60% and the total contribution discharge was about 36.56 × 106 m3, which was higher than inland mountainous areas as different elevation and climate. As the stable water source of river, the groundwater contributed 19.2–61.6% with average of 43.88%. The snowmelt water plays an important role in regional water balance. Owing to climate change, the snowfall period in Changbai Mountains was gradually shortening and extreme snowfall events were increasing. The results will provide evidence for further hydrological studies and help to plan future water management strategies in the alpine watershed. [ABSTRACT FROM AUTHOR]