天津市地下水流-地面沉降耦合模型

天津市平原区地面沉降主要由地下水大量开采引起，影响范围广、危害大，已成为天津市主要的环境地质问题。分析了研究区的水文地质条件，结合地下水开发利用状况，将研究区概化为6个含水层组，地下水流考虑三维非稳定流，地面沉降选用一维固结压缩模型，运用地下水流模型Modflow 2005和地面沉降模拟模块 Sub，建立了天津市平原区地下水流-地面沉降数值耦合模型，模型面积为1.1×10⁴ km²，利用1998-2008年地下水位等值线、过程线、地面沉降过程线等资料对模型进行了识别。模拟期的地下水均衡分析表明，在多年开采条件下，越流补给、压缩释水、侧向边界流入分别占深层含水层补给量的41.84％、32.15％和24.17％。将调试后的模型应用于南水北调实施后地下水控采条件下的地面沉降趋势预测，显示出停采或减少地下水的开采，有利于减缓地面沉降下降速度，且表现出开采层位越往下，地面沉降恢复难度越大的变化趋势。

An Integrated Numerical Groundwater and Land Subsidence Model of Tianjin

The land subsidence occurred in Tianjin Plain,mainly due to excessive use of groundwater resources,is characterized by affecting a wide range of area and causing serious damages,which has been a major environmental geology problem in Tianjin.In this study,firstly aquifer system in the area of study was discreted vertically into six layers based on the analysis of hydrogeological conditions of Tianjin in combination with current situation of groundwater exploitation.The groundwater was treated as three-dimensional transient flow and land subsidence model was adopted as one-dimensional consolidation/compaction model.The simulation model for both groundwater flow and land subsidence in Tianjin plain was developed by utilizing the groundwater flow simulation module-Modflow 2005 and the land subsidence simulation module—Sub package.Total area of the model domain is approximately around 1.1×104 km2,and the numerical model was identified using contours of groundwater table,groundwater hydrograph,and land subsidence process curve graph.The groundwater budget during the simulation period indicated that the water of vertical leakage between adjacent water-bearing units,compaction,and lateral inflow account for 41.84%,32.15% and 24.17% of the groundwater recharge of deep artesian aquifers respectively.Finally,the calibrated numerical model would be used to forecast trend of land subsidence under the control of groundwater exploitation after implementation of south-north water diversion project.The result shows that the decrease or cease in groundwater exploitation will contribute to the decrease in the rate of land subsidence.Moreover,the recovery of deformation of aquifer shows heterogeneity,with slow rate in the deeper aquifer.