Hydrological processes in continental valley basins: evidence from water stable isotopes

Abstract

• Runoff from continental valley basin is primarily recharged by groundwater. • Precipitation water vapor in continental valley basin is primarily influenced by external water vapor. • The cryosphere play a significant role in driving modifications in water resources within the basin. With the ongoing development of society and the intensification of climate change, the water resource crisis in arid regions is becoming increasingly severe. As the sole source of runoff in inland river systems, the continental alpine regions play a critical role in understanding the processes of water resource formation, migration, and transformation. Their hydrological processes are essential for predicting changes in basin water resources under future climate scenarios. This study takes the Xiying River basin in the Qilian Mountains as a case example, analyzing the hydrological processes in a continental valley basin through isotopic and hydrometeorological data collected from 2017 to 2020. The results of the study show that: (1) Precipitation water vapor in the Xiying River basin is mainly dominated by external water vapor, which is transported by westerly winds, with a relatively low percentage of water vapor in the direction of the southeastern and southwestern monsoons. (2) Precipitation is the main recharge source of river water and groundwater, while the main sources of runoff are groundwater, glacier-snow meltwater, and precipitation. The contribution of the three water sources to runoff is 62 ± 4 %, 17 ± 3 % and 21 ± 5 %. The study emphasizes that changes in the cryosphere are the primary factors influencing water resource variability in continental valley basins. The findings hold significant scientific value for understanding the eco-hydrological processes in arid high-altitude regions and for predicting the impacts of future climate change on basin water resources.