[Relationship Between Precipitation, River Water, and Groundwater Conversion in the Upper Reaches of Xilin River During the Rainy Season].

ABSTRACT

To deeply understand the hydrological cycle process and the transformation mechanism of different water bodies in the grassland inland river basin, the atmospheric precipitation, river water, and groundwater in the Xilin River Basin were taken as the research objects, the hydrogen and oxygen stable isotopes were analyzed, and the multi-scale spatio-temporal characteristics were analyzed to explore the quantitative transformation relationship between different water bodies in the basin. The results showed that① the Xilin River Basin had an obvious inland semi-arid climate, the atmospheric precipitation was the main source of recharge for the river water and groundwater, and the groundwater and river water experienced different degrees of non-equilibrium evaporation at the same time. ② The isotopic composition of the river water showed the characteristics of depletion in spring and autumn and enrichment in summer and showed a trend of increasing from upstream to downstream in space. The variation in δ18O in shallow and deep groundwater during the growing season was basically the same, and the main difference between the two occurred at the end of the growing season, that is, the former tended to be stable, whereas the latter showed an upward trend, which reflected that the deep groundwater had a lagged response to the infiltration and recharge of atmospheric precipitation and surface water, and both of them were depleted gradually from southeast to northwest in space. ③ Based on the estimation results of the endmember mixing model, the average recharge ratio of atmospheric precipitation and shallow groundwater to river water in summer was 52.69% and 47.31%, respectively, indicating that shallow groundwater was an important recharge source of river water in the inland river basin even during the rainy season. The results of this study provide theoretical guidance for water resource regulation and ecological environment protection in a typical semi-arid grassland inland river basin.