Origin and Dynamics of Saltwater Intrusion in a Regional Aquifer: Combining 3‐D Saltwater Modeling With Geophysical and Geochemical Data
Origin and Dynamics of Saltwater Intrusion in a Regional Aquifer: Combining 3‐D Saltwater Modeling With Geophysical and Geochemical Data
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DOI：
10.1029/2018wr023624
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发表时间：
2019-03
影响因子：
5.4
通讯作者：
R. Meyer;P. Engesgaard;T. Sonnenborg
中科院分区：
文献类型：
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作者：
R. Meyer;P. Engesgaard;T. Sonnenborg
在世界范围内，低洼沿海地区的含水层受到咸水现象的威胁，这是由于水头坡度小、地下水抽取率高以及对地貌的排水管理，这种情况可能会随着气候变化而加剧。数值模型可以作为确定盐分来源的工具，从而增加对驱动机制和控制咸水入侵程度的重要参数的了解。这样，就可以识别和管理容易受到海平面上升影响的地区。挑战包括未知的初始盐浓度、不均匀的地质和人为变化。在这项研究中，利用水文地质、地球物理和地球化学资料建立了一个依赖于密度的地下水流动和运移数值模型，目的是了解受咸水影响的地下水系统的历史及其对历史和未来变化的可能响应。模拟的咸水入侵范围与机载电磁数据相比很好，后者显示咸水深入内陆20公里。结果表明，咸水来源于侧向侵入海水和垂向入渗海侵水的共同作用。控制现代海水进入沿海含水层的主要特征是高渗透性的中新世深层砂岩含水层、提供优先流动路径的埋藏山谷以及延缓咸水入侵的广泛的中新世粘土层。人类活动增加了来自海洋的咸水流入，并导致了瞬变条件。未来的情景表明，由于非平稳性导致的咸水进程导致更深的含水层受到更严重的污染。气候变化主要影响浅层含水层系统。
Worldwide, aquifers in low‐lying coastal areas are threatened by saltwater occurrence, as a result of small head gradients, high groundwater abstraction rates, and drain management of the landscape, which is likely to intensify with climate change. Numerical models can serve as tools to identify the sources of the salt and thus to increase understanding of the driving mechanisms and important parameters controlling the extent of saltwater intrusions. This way, areas vulnerable to sea level rise can be identified and managed. Challenges include unknown initial salt concentrations, heterogeneous geology, and anthropogenic alterations. In this study, hydrogeological, geophysical, and geochemical data are used to develop a numerical density‐dependent groundwater flow and transport model with the objective to understand the history of a saltwater‐affected groundwater system and its likely response to historic and future changes. The extent of the simulated saltwater intrusion compares well with Airborne Electromagnetic data that show salt water up to 20 km inland. The results reveal that the salt water originates from a combination of laterally intruding seawater and vertically infiltrating transgression water. Main features controlling the progression of the modern seawater into the coastal aquifers are high permeable, deep Miocene sand aquifers, buried valleys that provide preferential flow paths in combination with extensive Miocene clay layers that delay saltwater intrusion. Anthropogenic activity enhances the saltwater inflow from the ocean and induces transient conditions. Future scenarios show that saltwater progression due to nonstationarity leads to enhanced contamination of the deeper aquifers. Climate change affects primarily the shallow aquifer systems.