Analysis of Water Chemistry Characteristics and Hydraulic Relationships of Different Water Bodies in Typical Mountain-oasis Systems in the Northwest Inland Area

Abstract

Kaidu River basin is a typical mountain oasis ecosystem in the northwest inland. Its hydrochemical environment information is of great significance to understand the regional hydrological process and optimize the allocation of water resources. Based on the collection of samples of various water bodies in mountainous and oasis areas in different seasons in 2020, this study analyzed the water chemical characteristics and hydraulic links in this region. The results showed that:① the water body in the study area was slightly alkaline as a whole, and the pH and TDS values showed the spatial changes of low in the oasis area and high in the mountain area; HCO3- and Ca2+ were the main anions and cations. The regional hydrochemical type was mostly HCO3--Ca2+, and the hydrochemical type of groundwater in the oasis area was more complex than that in the mountainous area. Regional hydrochemical changes were mainly controlled by rock weathering and human disturbance. ② The δ18O and δD values of the river water showed the seasonal changes of dilution in summer and enrichment in spring, whereas groundwater was depleted in winter and spring and enriched in autumn. Precipitation and glacial water did not change significantly within a year. In space, the δ18O and δD values of river water and groundwater showed the law of enrichment in the oasis area and dilution in the mountainous area. ③ The relationship between surface water and groundwater in the study area was close, and the transformation was frequent in summer. The relationship between surface water and groundwater in the oasis area was closer than that in the mountainous area. Groundwater in the oasis area was recharged by groundwater in the previous period, river water, and precipitation, and the recharge rate was usually groundwater in the previous period>river water>precipitation.