Study On Groundwater Compression Exploitation Scheme And Rehabilitation Effect In Tianjin Plain Area

Tianjin is short of surface water resources,long-term unreasonable exploitation of high intensity and inappropriate management of water resources have resulted in the continuous decline of groundwater level,which has led to serious land subsidence and other secondary disasters.The middle route project of the south-to-north water diversion project is a major measure to alleviate water shortage and ecological environment deterioration in the beijing-tianjin-hebei region,providing alternative water sources for compressed groundwater extraction.In this context,it is of great significance to carry out numerical simulation of groundwater flow and develop a compression mining scheme to restore and conserve groundwater resources.This study analyzes the distribution of groundwater funnel,establishes the numerical simulation model of groundwater flow,and formulates the compression mining scheme.The feasibility of compression mining scheme is analyzed through the analysis of water supply and demand balance according to the different situation of water supply and demand area in the south-to-north water diversion project.The groundwater flow model is used to simulate the distribution of near and long-term groundwater levels under the compression mining scheme,and the restoration effect of groundwater levels in typical funnel areas is analyzed.The main research results of this paper are as follows:(1)Firstly,this paper determined the distribution of typical funnel regions of each layer group in Tianjin.Based on hydrogeological conceptual model and groundwater flow mathematical model,the groundwater exploitation amount of different aquifer groups in towns,the exploitation amount of mining wells in cities,evaporation amount,source and sink items,water level of observation wells and initial water head are assigned to the Visual MODFLOW software platform to construct the groundwater numerical model.The model was validated by adjusting parameters,inversion of production volume and water balance analysis.The results show that the model is suitable for the simulation of groundwater flow field in the study area and the results of equilibrium analysis are also consistent with the actual situation of groundwater exploitation in tianjin.(2)Secondly,this paper designs compression mining schemes according to different compression mining targets,and makes statistical analysis on rainfall frequency of water source and water demand area.According to water diversion process data of water demand area in recent years,the amount of water diverted from the Yangtze River,Luanhe River and local surface water resources in different representative years were calculated to predict the short-term and long-term water consumption of tianjin.On this basis,supply and demand water equilibrium analysis is carried out for 5 different situations of supply and demand.The results show that the two compression mining schemes are feasible to use water quantity as the reference standard,except that both supply and demand areas suffer from dry years.(3)Finally,The groundwater level of Tianjin in 2020 and 2030 under different compression mining schemes is predicted by numerical model.Based on the spatial analysis function of ARCGIS,the changes of groundwater funnel area and the rising rate of central water level in each layer group are analyzed,and the repair effect of typical funnels in each layer group is analyzed.Although the two schemes of compressed groundwater exploitation have little effect in the short term,the long-term simulation results show that both of them have promoted the rise of groundwater level in Tianjin to a certain extent.The results of this study can provide a basis for Tianjin to formulate a reasonable groundwater exploitation plan and establish a scientific management mechanism.