Characteristics of stable isotopes in different water bodies in winter on the northern slope of Changbai Mountain and its environmental significance

Clarifying the mutual recharge relationship among diverse water bodies is a necessary foundation for the management and protection of water resources in river basins. Isotope technology is an effective method to investigate the composition of regional water resources and their recharge mechanisms. By systematically sampling the different water bodies on the northern slope of Changbai Mountain during winter as well as using meteorological data, the isotopic composition characteristics and hydraulic connections of different water bodies were analyzed, and an end-member mixing model was applied to quantify the recharge sources of river water. The results showed certain differences in the stable isotopic compositions of different water bodies in winter in the Changbai Mountain region. Precipitation depleted heavy isotopes, whereas groundwater and snowmelt water were relatively enriched in heavy isotopes. The isotopic points of river water, groundwater, and snowmelt water were located below the meteoric water line, and the slope and intercept of the evaporation line were low, thus indicating that these water bodies were affected by evaporation. The high-value points of river water isotopes responded to changes in the precipitation isotopes, thereby suggesting that the river water received direct recharge from precipitation. The isotopic value of Xiaohuangni River on the west slope of Changbai Mountain remained stable at a high level during the later observation stage, thus indicating that Xiaohuangni River may have received snowmelt recharge during that period. The end-member mixing results showed that the contribution rates of precipitation, groundwater, and Tianchi Lake water to Jianshui River on the northern slope of Changbai Mountain were 70.9%, 20.9%, and 8.2%, respectively, and 45.7%, 48.4%, and 5.9% to Erdaobai River, respectively. The contribution rates of precipitation, groundwater, and snowmelt water to Xiaohuangni River were 45.4%, 33.5%, and 21.1%, respectively. The differences in the recharge sources of river water in different basins and at different times were caused by temperature variations, underlying surface characteristics, and human activities. The results of this study can provide a scientific basis for regional water-resource development and ecological environmental protection.