| Manas River Basin is located in the arid area of northwestern China.It is a typical arid inland river basin,obviously characterized by low rainfall and large evaporation,the water resources are seriously inadequate.The lack of surface water resources makes groundwater an important available source of water.Multi-level reservoirs were built to relieve the water pressure caused by the uneven spatial and temporal distribution of water resources.But the construction of the reservoirs has changed the condition of groundwater recharge and excretion,making the regional water circulation more complicated.Therefore,this thesis establishes a model of groundwater in the plain area of Manas River Basin through the water balance method and numerical simulation method to study the influence of plain reservoir regulating on the groundwater level.The main research conclusions are as follows:(1)Using the water balance method to calculate the groundwater balance in the plain area of Manas River Basin in 2013.In 2013,the groundwater in the study area was in a negative equilibrium,the main factors affecting the groundwater level were groundwater exploitation,canal leakage and irrigation infiltration recharge.The total amount of groundwater recharge was 7.434×10~8m~3,the total discharge was8.073×10~8m~3,the difference was-6382×10~4m~3,the storage variable of groundwater was-7830×10~4m~3,the absolute equilibrium error was 1448×10~4m~3,and the relative equilibrium error was 1.95%.The result of groundwater equilibrium calculation provided a reference for the establishment and inspection of the numerical model.(2)Establishing a mathematical model of groundwater in the study area and use Visual MODFLOW to solve the model.The normalized root mean squared is less than 3%in the model calibration and verification period,and the head error in most areas does not exceed 1m.The numerical simulation results show that the total recharge of groundwater in the study area was 7.554×10~8m~3,of which the surface recharge,the groundwater lateral inflow,and the reservoir recharge accounted for 75.19%,21.22%and 3.60%.The total excretion of groundwater was 8.247×10~8m~3,of which the evaporation,spring water overflow,groundwater exploitation,and groundwater lateral outflow accounted for 27.07%,16.08%,50.90%and 5.95%.The groundwater in the study area was in a negative equilibrium,and the difference was-6927×10~4m~3.The numerical simulation results were basically consistent with those calculated by the traditional water balance method,the error was less than 10%,and the difference between the recharge and discharge is closer to the actual.The numerical model is of high reliability and stability and can be truly reflect the characteristics of the groundwater system in the study area.(3)According to the constructed groundwater numerical model,the change of groundwater level during different reservoir regulating is studied.When the reservoir run at operation water level,the leakage of the reservoir is 2735×10~4m~3,when the reservoir run at the lowest water level,the reservoir leakage was the smallest with 1347×10~4m~3,when the reservoir run at the normal water level and the leakage was the largest with 4185×10~4m~3.When the reservoir at the lowest water level,the groundwater level around the reservoir was lower than the operation water level,with a maximum decrease of 2.1m and a maximum average monthly decrease of 0.99m of the groundwater observation wells.When the reservoir at the normal water level,the groundwater level around the reservoir was higher than the operation water level,with a maximum increase of 1.5m and a maximum average monthly increase of 0.78m of the groundwater observation wells.(4)The reservoir regulating mode has an obvious influence on the change of the groundwater level around the reservoir.The nearer the reservoir is,the greater the influence of reservoir regulating,the maximum influence distance of the reservoir regulating on the groundwater level is 2000m in the upstream and 12000m in the downstream. |
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