Study On Water Environmental Isotopes In Northern Piedmont Of Tianshan Mountain

North part of Tianshan Mountain lies in the south edge of Zhungaer Basin,and is the most important economic and industrial development zone of West Development strategy in Xinjiang,also is the core of local economic construction with abundant land resources and mineral resources.However,it is very vulnerable in eco-environment because of many reasons, such as lying in the hinterland of Eurasia,belonging to typical continent aridity climate, ununiform space-time distribution,so water resources problem becomes the principal factor of restricting regional economic development and ecological environment restoration,whereas the core of water resources evaluation is relationship between precipitation-surface water and groundwater conversion.Therefore,the paper is based on "Monographic Study of the Groundwater Resources and its Environment Problem in Junggar Basin",and studies regional hydrogeological character and conversion relationship of precipitation-surface water and groundwater using Isotope Method,the results of which are very important for evaluation of the groundwater resources,reasonable exploitation and protection of the surface eco-environment.Some conclusions are as follow:1) According to study on distribution character of isotope and relationship betweenδD andδ¹⁸O,interrelationship among waters and recharge sources of groundwater are established;groundwater recharges elevation and mixing ratio of waters are calculated using elevation effect and mixing ratio of isotope,which further illustrate recharge,flow and drainage relationship of groundwater qualitatively and semi-quantitatively.2) Groundwater age is calculated using various models through tritium and ¹⁴C content. The result is as follows:tritium age in groundwater from intermont through dive in alluvial-proluvial fans to confined water in fine soil plain is about 30 years,Groundwater age increases gradually from 50 to more than 200 years,and ¹⁴C age from 5000 years to more than 10000 years.The results getting from ¹⁴C and tritium method are uniform in variation tendency,and the results show that groundwater runoff conditions in aquifer is more and more poorer,and further characterize runoff conditions3) The paper calculates groundwater renewal rate using tritium content of groundwater. The result shows:From diving water of piedmont area to confined water of fine soil plain, renewal rate of groundwater decreases from 5%to lower than 0.2%,which is uniform with variation tendency of groundwater age,and establishes a good basis for precipitation-surface water and groundwater conversion researches.4) Conversion law of precipitation-surface water and groundwater in Ma'nasi River basin is analyzed and conversion module is and summarized using Isotope Method and Hydrogeology Method.In the regions of water resources formation,recharges of groundwater are mostly alpine ice thawing water with the proportion 29%and conversion of rainfall infiltration with the proportion 71%;groundwater is converted to surface water in intrarnontane valley,the conversion rate of which is 46%.;surface water is converted to groundwater in alluvial- proluvial fans,the conversion rate of which is 70;in fine plain area, conversion occurs mostly in vertical direction and is from groundwater to surface water and then to precipitation,in which,conversion from groundwater to surface water occupies 77 percent,and conversion from surface water to precipitation occupies 25-41%.The achievements above have guiding significance for the correct evaluation of groundwater resource,and also have theoretical and practical significance for precipitation-surface water and groundwater conversion researches.