| The interaction between river and groundwater is one of the most common phenomena in nature, as well as is an important part of the hydrological cycle. With the construction of urban waterscape engineering, the urban eco-environment and quality were greatly improved, also the urban hydrological circulation system was changed, but a series of hydrogeological problems were brought about. In order to study the impact of artificial waterscape engineering on regional groundwater hydrodynamic field and water environment, by using of the Water Equilibrium Method, the Analytical Method and the Groundwater Numerical Simulation method, this paper took the rubber dam projects of Xi’an Chan-Ba Ecological District as example for calculating the seepage of river channel and explaining the impact of the rubber dam projects on regional groundwater seepage field. The main achievements are as follows:(1) The GA-BP model was employed to forecast the monthly precipitation, evaporation and runoff, which could provide database for calculating the seepage of river channel by using the Water Equilibrium Method and Groundwater Numerical Simulation Method.(2) Based on the precipitation, runoff, topography, and river cross section data of the study area, the stages of Chan-Ba River before and after the construction of rubber dam projects were obtained by the hydraulics software HEC-RAS. Besides, the monthly river channel seepage of NO.5 reservoir in Bahe River was calculated by the Water Equilibrium Method according to the stage-reservoir curve, the result show that the accumulative seepage from November,2014 to December, 2015 is 205.38×104m3.(3) The analytic formula of unsteady flow under the circumstance of a sudden change in the river stage was derived by studying the three stages of river channel seepage. As well as the change of groundwater level which affected by running the rubber dam projects was analyzed based on the pumping test data. Besides, the relationship between groundwater recharge and thetime change was simulated. The results show that the monthly seepage is 81.48×104m3 when the river stage raises 3 m.(4) Aimed at the influence of riverbed sediments on the hydraulic connection between river and groundwater, the vertical permeability coefficient Kvof Chan-Be riverbed were determined by In-situ Standpipe Test and Particle Analysis Method, then the comparison and analysis of calculated parameters were made.(5) The computational procedures of parametric inversion based on Excel was proposed and the diffusion coefficient of groundwater aand riverbed retardation coefficientβ were obtained by the Convolution Integral Method and Optimization Technique. As well as the aquifer parameters responding to the changes of groundwater level and river stage were calculated by inversion method according to the motoring dada of groundwater level and river stage. Based on the results of the above, the transient exchange capacity and accumulated exchange capacity between river and aquifer was obtained.(6) The hydro-geologic model and mathematical model of the study area were established.Then the Visual MODFLOWwas used to identify and verify the models. The results indicate that the models could reflect the real hydrogeological condition of the study area, as well as could be employed to evaluate the impact of rubber dam projects on the groundwater level.(7) The Visual MODFLOW and HEC-RAS combined model was built to present the groundwater-surface water coupling model. Taking the NO.5 rubber dam project as example, this model was used to study the connection between groundwater and river from three respects: groundwater flow field, hydrologic budget and groundwater level. In order to study the connection between groundwater and river, four scenarios were set, such as considering the aquitard in the bottom of the riverbed and the running of the rubber dam(A1), considering the running of the rubber dam but no aquitard in the bottom of the riverbed(A2), considering the aquitard in the bottom of the riverbed but no rubber dam(B1), no rubber dam or aquitard(B2). The results show that the groundwater recharge of B1 is 35.75×104m3, while the recharge of A1 is 176.7735.75×104, the amount of groundwater recharge increase 141.021×104, the growth is 394.46 percent.(8) Finally, the interaction between groundwater and river was analyzed by the Water Equilibrium Method, the Analytical Method and the Groundwater Numerical Simulation method, and the results calculated by the three methods, as well as the advantages and disadvantages of the three method were compared.This study is of significance to improve the utilization efficiency of the rubber dam in the reservoir area and analyze the interaction between groundwater and river. Moreover, it may provide basis for the construction of ecological civilization and economy. |
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