基于数值模拟的天津市地下水严重超采区演变分析

Analysis on over-exploited area evolution of groundwater in Tianjin city based on numerical simulation

天津市是华北地区典型的水资源短缺城市,地下水的长期超采已引发地面沉降等环境问题。为科学分析地下水开采现状,并预测压采条件下的地下水严重超采区演化趋势,本文采用基于有限差分原理的MODFLOW软件,建立了天津市平原区地下水流动的三维非稳定流数值模型,经识别和校正过的模型能准确反映人工开采引起的各承压层地下水位波动。基于该模型,分析了模拟期内(2003～2008年)地下水超采区的分布及演变过程;同时,预测分析了水资源配置制定的地下水限采方案,进一步剖析严重超采区的演变趋势,为南水北调实施后对天津市地下水的修复作用提供了可靠的分析手段和科学依据。预测结果表明,压采后地下水水位明显回升,主要开采层第Ⅱ、Ⅲ承压层的漏斗区基本消失,蒸发成为最主要的排泄方式。

Tianjin is a typical water-shortage city in the north plain of China.The environmental issues including land subsidence have been caused due to the long-term overexploitation of groundwater.In order to analyze the status of the groundwater exploitation and to predict the evolution of the over-exploited areas,the three-dimensional transient flow model is developed by using the software MODFLOW based on the principle of finite difference method,which could reflect the fluctuations in groundwater levels accurately after the identification and calibration.The evolution of the drawdown during the simulated period（2003～2008） is calculated based on the model.The scheme for decreasing groundwater exploitation is also predicted,and the development of the over-exploited areas is analyzed.The prediction provides an access to the remediation of the groundwater in Tianjin after the execution of the South-to-North Water Diversion Project.The predicted results show that the groundwater levels would rebound obviously after decreasing groundwater extraction,the funnel zones in the second and the third layers which are the main mining aquifers basically disappear,and the evapotranspiration is the main discharging pattern.