运城市地下水咸化趋势预测——准三维数值模拟方法

GROUNDWATER SALINIZATION IN YUNCHEN CITY PREDICATED BY A QUASI THREE DIMENSIONAL NUMERICAL SIMULATION

开采地下水引起运城市盐湖、硝池高矿化水倒补给而咸化地下水,是运城市一个严重的水环境问题。本文根据运城市的复杂水文地质条件,建立了一个“非均质五层结构越流系统准三维非稳定流”的数学模型,该模型突出考虑:(1)弱透水层由于水头升降而储水或释水;(2)降雨入渗补给潜水的滞后效应;(3)蒸发强度随潜水面埋藏深度、包气带岩性和植物生长变化而变化的特征,该非线性复杂的数学模型采用有限单元数值法求解,利用所建立的模型模拟并选定较优的三种方案,预测实施十年(1990年～1999年)地下水的咸化趋势并作出定量评价。

The high mineralized water of Xiaochi and Yanhu, recharging inversely into aquifer caused by groundwater extraction, is a big aquatic environmental problem in Yunchen city. According to very complex conditions on hydrogeology of research area, a quasi three dimensional numerical model, which describes the leaky system of unsteady flow with nonhomogeneous five-layer structure, is presented in the paper. This model lays special stress on considering the three main points: (1) hysteresis effect of rainfall infiltration; (2)groundwater release or storage from aquitard by water head rising or falling; (3)evap-ortranspiration intensity varied with the depth of water table, lithology of aeration and plants. The non linear complex mathematical model is solved by the numerical method of finite element. Based on the model, three selected schemes are run on the computer. Salinization tendency of groundwater is predicated and evaluated at Yunchen city in the future ten years from 1990 to 1999.