Study On The Hydraulic Connection Between Surface Water And Groundwater In Kaidu River Basin Based On Hydrochemistry And Stable Isotope Technology

The Kaidu River Basin is a typical inland river basin in the arid and semi-arid regions of northwest China.It is one of the important animal husbandry bases in Xinjiang and an important water source guarantee in southern Xinjiang.The Yanqi Basin downstream is an important oasis agricultural area in Xinjiang.The Kaidu River is of great significance for ecological water transport in the lower reaches of the Tarim River.In recent years,with the continuous global climate change,coupled with the increase in population in the river basin and the rapid expansion of oasis,the overexploitation of surface and groundwater resources has led to the increasingly serious contradiction between the supply and demand of regional water resources.The regional water environment caused by this has continued to deteriorate.In particular,the annual runoff caused by diversion irrigation,evaporation,and seepage in the oasis area of the basin below the mountain pass is continuously increasing,which is rapidly increasing,leading to a sharp decrease in the amount of water injected into the Bosten Lake downstream,and changes in the surface and groundwater quality in the basin.The resulting water security issues are also seriously threatened.The study of the spatial-temporal variation of water chemistry in the Kaidu River Basin and its main controlling factors,as well as the spatial-temporal distribution of water quality,is conducive to understanding the analysis of the relationship between surface water and groundwater conversion in the Kaidu River Basin.The rational coordination and utilization of resources,the study of similar water environment issues in arid and semi-arid regions in China,and the maintenance of the ecological environment and economic development in the ethnic minority areas of southern Xinjiang are of great significance.In this paper,the inverse distance weighted spatial interpolation method was used to analyze the surface water and groundwater hydrochemical characteristics,stable isotope characteristics,and the spatial and temporal distribution characteristics of water quality in the Kaidu River Basin.The Piper three-line diagram method was used to interpret the surface and groundwater chemical types in the basin.The Gibbs diagram interprets the analysis of the main ion source of surface water and groundwater in the basin,and uses the two-terminal mixed water source segmentation model to quantitatively analyze the conversion relationship between surface water and groundwater in the basin.The results show that:(1)The surface water and groundwater in the Kaidu River Basin are neutral to slightly alkaline in each season,and the degree of mineralization is low.Na+and Ca²⁺are the main cations and HCO₃^-and SO₄^2-are the main anions.The chemical types of surface water in each season are mainly HCO₃^--Ca²⁺-Na⁺and HCO₃^--Ca²⁺,and the chemical types of groundwater in each season are HCO₃^--SO₄^2--Na⁺-Ca²⁺and HCO₃^--Na⁺-Ca²⁺.(2)In the main ion spatial distribution,the spatial differences of Ca²⁺in cations are the largest,and the spatial distribution characteristics of K⁺,Na⁺,and Mg²⁺are similar,and the differences are not large.The difference in the spatial-temporal distribution characteristics of the anion HCO₃^-is most obvious.The relatively high values of major cations and anions on the surface of each season are mostly distributed in the downstream area in the southeast of the basin.(3)Carbonate weathering is the main factor controlling the source of surface water and groundwater ions in each season of the study area.Human activities during the crop growing season(summer)and irrigation season(spring,autumn)have a significant impact on the surface water and groundwater Have a certain impact.(4)The quality of surface water and groundwater in summer and autumn is good,and it can be used as a source of irrigation water for farmland.The spatial difference between surface water and groundwater quality is basically the largest in spring.Groundwater quality The quality of groundwater in each season is better in the middle and upper reaches and worse in the downstream.(5)Precipitation in each season in the study area is the main form of surface water recharge.The characteristics of surface water and groundwater isotopic composition in spring are most different in each season.The stable isotope of surface water on the northwest side of the Huangshuigou and the downstream Yanqi Basin in each season Relative enrichment,stable isotopes of groundwater in the lower reaches of the river basin in each season are more abundant than in the upper reaches.(6)In the oasis area of the study area,the surface water and groundwater are hydraulically connected during the dry season.The average recharge ratio of river water to groundwater in spring in the oasis area of the study area was the largest,46.8%,and the smallest in autumn was 19.9%.The average recharge ratio of precipitation to groundwater was the largest in autumn,12.0%,and the smallest in spring,3.4%.