Numerical Simulation And Prediction For The Groundwater System Evolution Of Zhengzhou Riverside Well Field

The riverside water source of Zhengzhou is located in the south of the Yellow river,in the northeastern of Zhengzhou city.In recent years,rapid urbanization,flow cutoff of the Yellow river and deterioration of water quality have resulted in gradually decrease of safety water.In order to solve these problem,some riverside water sources exploiting shallow groundwater have been built,e.g.,the Beijiao water source,the Jiuwutan water source.To assure the safe running of water source for a long time,it is necessary to make an assessment of the groundwater system under the pumping condition,to analyze the trend of variation of groundwater resource,which could provide reference for designing sustainable use of groundwater.Through collecting hydrogeological data of the study area and implementing some field work,the hydrogeological condition was established and the study area was divided into two aquifers,an unconfined aquifer and a confined aquifer.By using the groundwater flow model software GMS,a steady groundwater flow model and a transient groundwater model with the period from January 1 1995 to December 312013 were developed.The model was corrected by the trial-error method,and the simulation result shows that the groundwater flow model is reliable.In addition,the budget calculation result demonstrates that the study area is under negative balance condition.Analysis of groundwater budget and groundwater flow field of different period shows that the deficit of groundwater increases with the increase of groundwater pumping.Meanwhile the groundwater flow field and boundary conditions change a lot.A cone of depression is tend to be formed too.Through analyzing the composition of groundwater budget,it is found that the amount of Yellow river seepage accounts for about 50 percent of the total amount of groundwater pumping,and it also accounts for 41.25 percent of the amount of water exploited by the new water resource.A prediction model with the period from 2014 to 2033 was developed to simulate groundwater flow under present withdrawal and potential maximum withdrawal.The simulation result shows that the amount of available annual groundwater withdrawal from the unconfined aquifer is 393.10 million cubic meter,and the amount of that from the confined aquifer cannot exceed 23.58 million cubic meter.That is,the unconfined aquifer has more advantage on safety groundwater withdrawal than the confined aquifer.It is because the unconfined aquifer is easier to motivate the Yellow river seepage as well as capture surface discharge(e.g.discharge to the Jialu river,evaporation),but the recharge way of the confined aquifer is simple and its recharge rate is very slow.