承压水潮汐荷载效应研究进展

Review of research on tidal loading effect on groundwater dynamics in confined aquifers

地下水潮汐效应是滨海地区水文地质研究的一个重要方面,潮汐荷载效应是承压水潮汐效应的动力学机制之一。介绍了国内外潮汐荷载效应的研究进程,系统地总结了解析法和数值法在潮汐荷载效应研究中的应用及取得的成果。解析法是潮汐荷载效应研究的主要方法,该方法多通过荷载系数来刻画潮汐荷载效应,能够较清晰、准确地揭示复杂含水层结构、多种影响因素、复杂边界条件下的地下水潮汐效应规律;数值法主要通过三种方法(现有地下水水流数值模型改进法、荷载系数法和半数值法)来实现对潮汐荷载效应的研究。在现有潮汐荷载效应研究中,上述两种方法都很少考虑应力和孔隙渗流的耦合。程序化、高效化和可视化使得数值法仍应作为滨海区复杂水文地质条件下地下水动态的主要研究方法。为此,通用的地下水数值模拟代码(MODFLOW)需要改进,使之能够实现对潮汐荷载效应的刻画。另外,承压水作为滨海区(如:大陆岛)重要的淡水资源,人为开采是地下水动态的主要影响因素之一,滨海区地下水动态研究应综合考虑人为因素和潮汐荷载效应的共同作用。

Tide-induced groundwater dynamics in coastal aquifers is an important research aspect in coastal hydrogeology. The ocean tidal loading is one of the main mechanisms for the groundwater dynamics in coastal confined aquifers. This paper reviews the domestic and oversea progresses of analytical and numerical studies on tidal loading effects on groundwater dynamics. As the clear solution for groundwater dynamics in coastal aquifers,the analytical method is the main and important method for research on tidal loading effects. The analytical method has been used to analyze the tide-induced groundwater dynamics in multi-layered aquifer system with considerations such as roof of confined aquifer extending under the sea,leakage through the semipermeable layer from upper unconfined aquifer or ocean,storage of semipermeable layer,loading effects of water table variation in the unconfined aquifer,submarine outlet-capping and submarine springs. On the other hand,despite limited applications in research on tidal loading effects,the numerical method is also used to analyze the tidal loading effect on groundwater dynamics through three ways including improving the codes of a numerical model,incorporating the loading term in the model and semi-numerical simulations. It is a pity that the coupled stress with groundwater flow is rarely used in researches on tidal loading effects on groundwater dynamics. In our opinion,the programmatic,efficient and visualized numerical method should be the main method for research on groundwater dynamics in the aquifer system with complicated hydrogeological conditions. The widely used numerical models such as MODFLOW should be revised to simulate the tidal loading effects. It should be noted that the combined effects of tidal loading and pumping need to be considered in the future research on tide-induced groundwater dynamics in confined aquifers containing important freshwater resources in coastal area.