Study On Groundwater Circulation Mechanism And Model Of Development And Utilization In Zhangye Basin

Zhangye basin,located at the drought area in northwest of China and belonging to the midstream of Heihe River,is one of the most important agricultural bases in China.It is characterized by its drought and water shortage throughout the year.The groundwater,as an important component of water resources,is beneficial to economic development and social stability in local areas.The study of the groundwater circulation mechanism plays an important role both theoretically and practically in guiding the reasonable evaluation,exploitation and utilization of groundwater resources.This thesis is supported by two projects,namely,"Observation and Mechanism Research of Mutual Transformation between Surface Water and Groundwater in Heihe River"by the National Science Foundation and "Hydrological Geology Survey in the Key Areas of Heihe River" by the Bureau of China Geological Survey.The motif of this thesis is about the study of models about groundwater circulation mechanism and its exploitation and utilization in Zhangye Basin.Based on analysis of spatial and temporal evolution of basin and its characteristics of boundary,the thesis revolves around the investigation on basin’s aquifer space structure,dynamic field,chemical field and temperature field of groundwater,and then it regards the relationship among groundwater recharge,mining water level and overflow excitation response as the starting point and puts forward the model of development and utilization of groundwater resources after quantitatively analyzing groundwater circulation mechanism.The results of the study are shown as follows:Constructing the spatial distribution of aquifers,based on the analysis of the progress of evolution,characteristics of the boundary,the elevation of basal and the thickness of unsaturated zone of the basin,can lay the foundation for studying on groundwater circulation mechanism.The groundwater circulation is strictly controlled by the boundary of aquifers and the characteristics of the base.It includes the research of temporal and spatial changes of the groundwater levels and the characteristics of hydrodynamic field in the intra-annual and annual period and also the analysis of the hydrochemical characteristics,the isotopic characteristics,the change of the hydrogeochemical field and the temperature field of the groundwater.Built on the study of relationship among groundwater recharge,mining water level and overflow excitation response,it reveals the groundwater circulation mechanism can be summarized as "three Replenishment-three drainage",which refers to the infiltration of river water,channel water,irrigation water and the flowing,the exploitation and the evaporating of groundwater.To address the issues on exploitation and utilization of groundwater,the thesis analyzes the recharging of the groundwater by supplement from the water projects to ensure the infiltration of river water from the Caotanzhuang reservoir to the Heihe River Bridge,the controlling of exploitation on the groundwater resources and the groundwater extraction in the irrigation season and limiting on the number of the reservoir.According to analysis,the model of exploitation and utilization of groundwater is to enhance the recharge,control the amount of exploitation and coordinate the ways of exploitation to solve problems about drought.