The Study Of Groundwater Recharge And Renewal Rate In Wu-ling Irrigation Area

Wu-Ling Irrigation Area is located in the northwest arid region of China.The precipitation of Wu-Ling is scarcely and it has strongly evaporation,rarely surface runoff,very fragile ecological balance.Groundwater resources are not only an important water source for the industrial,agricultural and household water of Wu Ling region,but also has played a vital role to the ecological environment of Wu-Ling region.In response to the western development strategy,the sub-topics Lingwu Daquan groundwater circulation mechanism research of the implementation project named"groundwater exploration in Ningdong energy base"was carried out by the Geological Survey of China Geological Survey Bureau.The research of this paper based on this project,using mixing cell model to evaluate groundwater recharge of the study area quantitatively on the basis of qualitative groundwater circulation patterns and using radioactive isotopes tritium to calculate the groundwater renewal rate of the study area.First.the construction of Wu-Ling groundwater circulation pattern.Comprehensively analyzed the topography,dynamic of phreatic aquifer and confined aquifer,hydrochemistry,stable isotope characteristics of study area concluded that the topography controls mesa groundwater flow direction,general the flow direction is from east to west,from southeast to northwest.the same with the change of topography.The tilted Alluvial porosity and fracture phreatic resive the recharge fron the surface water of the eastern low mesa,groundwater through fractured zone and deep groove in the form of underground runoff to recharge the porosity confined aquifer of sloping plain area.The groundwater of tilted alluvium and lacustrine plain after receiving the recharge,in the form of lateral runoff to recharge the wesrtern lacustrine plain area groundwater.The main recharge of alluvium and lacustrine phreatic is irrigation water which from the Yellow River.The flow direction of alluvium and lacustrine phreatic is southwest.The alluvium phreatic discharge to aqueduct and by way of evaporation and exploitation.The alluvium and lacustrine confined water resives the recharge from phreatic and lateral runoff,discharged by exploitation and runoff.Second,quantitative evaluation of Wu-Ling groundwater recharge.Using the hydrochemistry and isotopic data of different aquifer in the study area,combined with hydrogeological condition established and solved the mixing cell model of unconfined and confined aquifer.The unconfined aquifer mixing cell model result showed that the main recharge of unconfined aquifer is the irrigation water.There is 71.65%of the total amount of phreatic recharge from irrigation water.18.59%of the total amount of phreatic recharge from eastern mesa lateral runoff,9.76%of the total amount of phreatic recharge from southern mesa lateral runoff.The cells near the mesa resive the irrigation recharge is little.all are below 50%,on the other hand the cells near the Yellow River resive the irrigation recharge is much..The confined aquifer mixing cell model result showed that the main recharge of confined aquifer is the lateral runoff.There is 68.36%of the total amount of confined water recharge from lateral runoff in which30.98%of the total amount of confined water recharge from eastern mesa lateral runoff,37.39%of the total amount of confined wate recharge from southern mesa lateral runoff,31.64%of the total amount of confined water recharge from phreatic.Third,the renewal rate of Wu-Ling groundwater.Restored the irrigation water and precipitation historical series of tritium values in the study area,estimated the average annually renewal rate of unconfined aquifer and confined aquifer.The result shows that the renewal rate of unconfined aquifer at the vicinity of Da-quan,Haojiaqiao,Dumuxiang and Chongxingxiang is more than 3%,it bigger than other place.At the edge of Yellow River,the unconfined aquifer renewal rate is about 1.5%.The trend of the unconfined aquifer renewal rate is that the distance to the Yellow River the closer the smaller.The confined aquifer renewal rate at Daquan and Lingwu is bigger than other place,it about 1%,in addition the place between Daquan and Lingwu is also bigger than other place.Combined with the actual can know that a place where has bigger groundwater exploitation the renewal rate of groundwater is bigger.