Study On Numerical Simulation Of Shallow Pore Groundwater Flow In Changzhi Basin

Changzhi basin is located in the southeast of Shanxi Province,Most of the source of Nanyuan of Zhuozhang river flows through the area.The shallow pore groundwater in the area is closely related to the surface water.It is an important aquifer system in the upper reaches of Zhanghe River.In recent years,the unreasonable exploitation and utilization of shallow groundwater in the basin has caused some problems,such as the continuous decline of groundwater level,the aggravation of water pollution and the serious waste of water resources.First of all,the basin is determined by the surface water supply of shallow pore groundwater.Then,the sand tank model is constructed,and the experimental results are analyzed by analytical solution and numerical solution.The error between the analytical results and the observed values is very large,which is mainly caused by neglecting the vertical velocity of the water.Numerical simulation results show that under the premise of the credibility of 97%,the maximum relative error of the simulated water level value is 0.102 m,the minimum value is 0.001 m,and the relative error is 0.023 m.The results of numerical simulation are closer to the observed values.Based on the analysis of the geological and hydrogeological conditions of the basin,the characteristics of groundwater recharge and discharge and the dynamic types of groundwater,the concept hydrogeological model was generalized.According to the lithology and empirical value of aquifer.According to the hydrogeological conditions,the conditions of rainfall evaporation,the condition of river recharge and discharge,to determine the boundary conditions in the numerical simulation and source sink.On the basis of this model,a heterogeneous isotropic two-dimensional unsteady flow model is constructed.Using the water level observation data in 2010 and 2011,20 typical observation holes in the basin are selected to validate the model.The water level of observation well is fitting better in identification period.Observation well fitting error less than 0.50 m accounted for 80% of the total.The simulated values and observed values of groundwater flow field are well fitted.The water level of observation well is fitting better in Verification period.Observation well fitting error less than 0.66 m accounted for 75% of the total.The simulated values and observed values of groundwater flow field are well fitted.The sensitivity of the identified model is calculated.Local sensitivity analysisshows that the change of K value has a great influence on the sensitivity of the model.The decrease of the permeability coefficient has a greater influence on the groundwater level of the shallow layer.The decrease of Sy value of water supply is also greater than that of the average shallow groundwater.The results of global sensitivity analysis reveal the same law.At the same time,it is shown that the sensitivity of the combined parameters is not a single parameter sensitivityApplication of the model,set up three kinds of mining plans to predict,the results show that the long-term evolution of groundwater level is decreasing,and in Tunliu,Zhangzi,suburbs and other places of groundwater level decreased significantly.Scheme two shows that the water level decreases obviously in the north central part of the basin and northeast of the Zhangzi County.Plan three shows that the increase of the amount of the exploitation of the groundwater level in the region has been more obvious effect of 10%,the local water level has fallen sharply.The three prediction programs in 2015 water are measured in the order of-2401 million cubic metre,-2744.7 million cubic metre,-4357.5 million cubic metre.