Study On Hydrochemical Field And Renewal Of Different Water Bodies In Ulungur River Watershed

The Ulungur River Watershed belongs to the Altai Mountains in Xinjiang,which rainfall has been scarce for many years and the efects of evaporation and vegetation transpiration are relatively intense,the water resources distribution is ramarkably unequal in the basin.For nearly two decades,As a result of the fast development of industrial?agricultural and animal husbandry,the poverty of water resources has become a crucial constraint to the social development of the watershed and the productive activities of the local residents.Meanwhile,problems such as soil erosion,soil desertification,salinization,and the destruction of ecosystem stability are prominent in the area,and the unreasonable management and utilization,of water resources in the region has further aggravated environmental and geological problems.Groundwater and surface water are the main water supply sources for production activities in the basin,It is also the key problem of regional water resources evaluation.This article is based on the collection of geological and hydrogeological data of the Urungu River Basin,combined with field investigation and water chemistry sample test results,this paper is guided by the theory of regional water circulation,comprehensive use of hydrogeochemistry and water environmental isotope analysis methods,Ascertained the spatial distribution characteristics of major ion components and stable isotopes in various water bodies in the area,and reveals the formation factors and evolution direction of the water chemistry characteristics of the basin,Comprehensive use of hydrogeochemistry and isotope analysis methods to find out the formation factors and evolution direction of the water chemical field in the watershed,and finally use the geomorphic unit as the structure to reveal the mutual transformation mode between the different water bodies.The main findings arc as follows:(1)The variation of the major components of the river water is same with phreatic water,and both show an obvious increasing trend.The type of river water quality transitions from upstream to midstream that the water quality is generally better than of the phreatic waters.Among the chemical types of surface water,the Ulungur River water undergoes the transformation process of three water types:HCO3-Ca·Na?HCO3·SO4-Ca·Na?SO4·HCO3-Ca·Na,Both Ulungur Lake and Jili Lake are SO4·Cl-Na type water.Among the chemical types of groundwater,phreatic water from the eastern bedrock mountain area to the western plain area along the route:HCO3·SO4-Na·Ca?SO4·HCO3-Na·Ca?SO4-Na·Ca?SO4·Cl-Na four types of water chemistry changes.The content of major ions in confined water is quite different from that of other bodies,except for Cl-,the spatial distribution of ions is relatively stable,the north and south sides of the Ulungur River are mainly SO4·Cl-Na·Ca type water,and Cl·SO4-Na·Ca type water is widely distributed near the two lakes.Its water chemistry characteristics,water source and formation,groundwater renewal ability not only helps to reveal the transformation relationship between the various water bodies in the region,(2)The spatial evolution characteristics of groundwater chemical components in different geomorphological units are jointly affected by the structure of the envelope belt,topographical features,geological structure,hydrodynamic conditions and hydrogeochemical.The low mountainous area of the bedrock and the mountain valley are affected by different degrees of cation exchange and the weathering of rocks.The bedrock hills and low mountains and alluvial plains are jointly controlled by rock weathering?evaporation and concentration,and the confined water is mainly affected by cation exchange and replenishment water sources.The evolution trends of the chemical characteristics of groundwater and surface water evolve towards the Cl-Na type and Cl·SO4-Na type with high salinity respectively.(3)The local rainwater line equation was established:?D=6.49?18O-8.63(R2=0.98),the slope of which is smaller than that of the global and Chinese rainwater lines,showing a typical drought?climatic characteristics of semi-arid areas.The water sample points are distributed on both sides of the local rainwater line,and all receive atmospheric rainfall replenishment.Affected by evaporation,the water weight isotope content was from large to small is Ulungur Lake>Jili Lake>River>phreatic water>confined water.(4)The results of radioisotopes 3H and 14C show that the groundwater renewal rate and spatial age distribution in the study area are quite different.The renewal rate of phreatic water from the low mountainous area of the bedrock to the alluvial plain is finally reduced from more than 3%/a to 1%/a,and the renewal rate in the central and northern alluvial plains is less than 1%/a;the overall confined water renewal rate is Less than 0.07%/a,the renewal rate of confined water under the mountain valley is close to or greater than about 1%/a.In the groundwater age distribution,phreatic water is modern water;The age of confined water fluctuates from modern water to ancient water,with an average age greater than 15000 a.Among them,the Ulungur River is the boundary between the north and south of confined water,and the age of confined water in the north(18000a)is greater than the southern part(<10000a).(5)The conversion between surface water and groundwater in the watershed is relatively complicated.The whole process is mainly recharged by phreatic water to the river water,and the two lakes are the final discharge points of each water body.The mountain valley and the flood plain area are converted between river water and diving In addition,the phreatic water of the geomorphological units has been recharged to the confined water,and the vertical recharge intensity has gradually weakened from the bedrock mountain area to the alluvial-proluvial plain.