苏北沿海三市三维地下水流数值模拟

20世纪80年代以来，苏北沿海三市（连云港、盐城和南通）地下水过量开采导致部分地区水位持续大幅下降，引发地面沉降、水质咸化等问题。本文基于研究区大量地质、水文地质资料，以及2005—2013年地下水开采和水位观测数据，经过模型识别、验证，建立了能刻画苏北沿海三市地下水流场演化的三维非均质各向异性地下水流数值模型，模拟了研究区2005—2013年开采量由约2.03亿m³逐渐减少到1.56亿m³条件下深部地下水系统流场（包括第Ⅱ、Ⅲ、Ⅳ承压含水层）的动态演化过程。结果表明，各观测孔的水位实测值与模拟值吻合良好，水位及水均衡模拟结果显示各含水层水位下降得到有效控制，但是该区域地下水仍处于超采状态。为进一步控制水位下降，防治咸水扩散、地面沉降等地质环境灾害，模型预测并比较了现状开采和限制开采2种不同开采方案下2014—2020年苏北沿海三市深层地下水流场的变化趋势。预报结果显示，2种开采方案下，各含水层水位下降速率均减小，尤其是限制开采方案下，第Ⅱ、Ⅲ和Ⅳ承压含水层的区域水位平均下降速率依次为0.15、0.16和0.15 m/a，分别比模拟期减小了46.43%、65.21%和48.28%，在开采强度降至最低的条件下储存量变化速率仍为负值，说明需要进一步加强地下水限制开采的力度。

Numerical Simulation of Three Dimensional Groundwater Flow in Three Coastal Cities of North Jiangsu

Since 1980s, the over-exploitation of groundwater has caused a significant and persistent decline of water levels in some areas of the three coastal cities of north Jiangsu (Lianyungang, Yancheng, and Nantong), land subsidence, water salinization, and other issues. Based on the previous study and the boreholes and water level observation data from 2005 to 2013, the authors established a three dimensional heterogeneous anisotropic groundwater flow numerical model. It can truly calculate the evolution of groundwater flow field in this area after calibration and verification. The groundwater flow was simulated between 2005 and 2013, and the calculated results fitted the observation data well for every observation well. The simulation results of water level and water balance showed that the decreases of groundwater levels of every confined aquifer were effectively controlled through reducing the groundwater exploitation, although the groundwater in this area was still in the state of over exploitation. In consideration with the requirement of controlling geological environment disasters including salt water diffusion and land subsidence, the model predicted and compared the evolution of deep groundwater flow fields (including the confined aquifers Ⅱ, Ⅲ and Ⅳ) under two different exploitation strategies until 2020. The predictions revealed that the decreases in groundwater levels of every confined aquifer under two strategies were well controlled. Especially with the control exploitation strategy, the average decreasing rates of the confined aquifers Ⅱ, Ⅲ, Ⅳ were 0.15, 0.16 and 0.15 m/a respectively, which were reduced by 46.43%, 65.21% and 48.28% comparing with that in the simulated period in this study. The negative variation rate of storage volume under the lowest pumping intensity suggests that it is necessary to further reduce the exploitation of groundwater.