| The theory of groundwater flow system is of great significance for deepening the understanding of the formation and evolution of geological processes,and the osmotic structure of water bearing system is an important factor to control the development of groundwater flow system.Previous studies on heterogeneity of aquifers are mainly based on the structural characteristics of heterogeneity,that is,the permeability coefficient is determined in space and obeys the probability distribution regularly,such as the homogeneous case(Tóth,1962),the stratiform distribution(Freeze,1967,Winter,1978)and the compaction condition(Jiang X W,2009),and a random distribution of study is less.Due to inadequate understanding of aquifer infiltration structure,the understanding of the influencing factors of groundwater flow system is far from complete.The existing methods of describing aquifer heterogeneity can not be fully applicable to the actual conditions.Therefore,it is necessary to explore and further improve the characterization of Aquifer Heterogeneity.In view of the above problems,this paper takes the typical section in northern Ordos Basin as an example to carry out theoretical research.The heterogeneity of aquifer is controlled by three factors: horizontal correlation length,anisotropy value and variance of permeability coefficient K.The following research has been carried out.(1)On the basis of fully collecting and analyzing the results of previous studies,we will understand the current situation,main trends and problems of heterogeneous characterization of aquifer.(2)Based on the model of the Tóth small submersible basin,the GMS software is used to establish the two-dimensional simulation of the section.The flow pattern and the age distribution of groundwater under the heterogeneous anisotropic condition of the osmotic coefficient K are investigated,and the effects on the groundwater flow system are compared with the simulation results under the homogeneous anisotropic condition.(3)The simulation and the dynamic field and age distribution of the actual water system are compared to verify the feasibility of the model.The results show that the growth of the three cycle system can be seen by the increase of the correlation length,anisotropy and the K variance of the permeability coefficient of the single control.The change process of the groundwater flow system is the change of the two stage circulation system from the local circulation and the intermediate circulation to the three level circulation system of the local circulation,the middle cycle and the regional circulation.The age distribution of groundwater is the age of deep groundwater.Compared with the measured data of stratified water level and groundwater age,the model simulation results are consistent with the measured level of stratified water level and groundwater age,which proves that the heterogeneous method can be used for simulation.The results not only have a deeper understanding of the factors that influence and control the development of the underground flow system,but also promote the practical application of the theory of groundwater flow system. |
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