Impacts of Subsurface Dam Construction on Downstream Groundwater Levels and Salinity in Coastal Aquifers
Impacts of Subsurface Dam Construction on Downstream Groundwater Levels and Salinity in Coastal Aquifers
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DOI：
10.1111/gwat.13304
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发表时间：
2023-03
期刊：
影响因子：
2.6
通讯作者：
Jiaqi Liu;P. Brunner;T. Tokunaga
中科院分区：
文献类型：
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作者：
Jiaqi Liu;P. Brunner;T. Tokunaga
地下水坝是一种很有前景的地下水资源开发工程技术。然而，这些水坝对地下水环境可能产生的影响一直是人们关注的焦点。在这里，我们使用三维（3D）、变密度、非饱和地下水流模型来探讨在无承压沿海含水层的淡水域中修建的地下水储存型地下坝如何影响下游地区的地下水位和盐度。模型结果表明，地下大坝建成后，下游地区地下水位在强降雨过程中出现阶段性超前、幅度更大、频率更高的波动。不同地下大坝情景的数值模拟表明，随着坝顶高程的升高或距海岸距离的缩短，地下水位波动进一步加剧。而且，在地下水库补给期间，下游地区的海水从原来的位置向陆地侵入，至少会暂时威胁海岸附近的水质。坝顶高程越高，海水入侵的持续时间越长，而靠近海岸的大坝则导致海水入侵的水平范围更大。讨论了关于改进地下大坝的评估方法和工程设计的一般含义。
Subsurface dam is a promising engineering technology for groundwater resources development. However, the possible impacts of these dams on the groundwater environment have been a major concern. Here, we used a three‐dimensional (3D), variable‐density, unsaturated‐saturated groundwater flow model to explore how a groundwater‐storage‐type subsurface dam, built in the freshwater domain of an unconfined coastal aquifer, affected groundwater levels and salinity in the downstream area. Model results suggested that, after subsurface dam construction, groundwater levels in the downstream area showed intensified fluctuations in terms of phase advances, greater amplitudes, and higher frequencies following heavy rainfall events. Numerical simulations with variable subsurface dam scenarios indicated that the groundwater level fluctuations were further intensified with a higher crest elevation or a shorter distance from the coast. Moreover, during the recharging period of the subsurface reservoir, sea water in the downstream area intruded landward from its initial location, which can at least temporarily threaten water quality near the coast. A higher dam crest elevation prolonged the duration of sea water intrusion, while a dam positioned closer to the coast induced sea water intrusion with a greater horizontal extent. General implications are discussed with respect to improving assessment methodologies and engineering designs of subsurface dams.