Preferential flow can result in rapid contamination of groundwater resources. This is particularly true in aquifers with connected, high permeability geologic structures and in coastal systems where the oceanic source of contamination is ubiquitous. We consider saltwater intrusion due to pumping in volcanic aquifers with lava tubes represented as connected high‐K structures and compare salinization responses to those of heterogeneous aquifers with different structure and equivalent homogeneous systems. Three‐dimensional simulations of variable‐density groundwater flow and salt transport show that conduits formed by lava flows create preferential groundwater flow in volcanic aquifers. These conduits allow fresh groundwater to extend further offshore than in other systems. However, onshore pumping causes saltwater to migrate landward quickly through the conduits relative to the other models, resulting in more severe saltwater intrusion, particularly at shallow depths. The geometry of geologic heterogeneity in volcanic aquifers leads to increased risk of salinization of fresh groundwater as well as substantial uncertainty due to significant spatial variation in saltwater intrusion. The findings illustrate the importance of considering geologic heterogeneity in assessing the vulnerability of coastal freshwater resources in volcanic and other aquifers with connected high‐permeability geologic structures.

中文翻译：

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优先流量增强了火山岩含水层中抽水诱导的盐水入侵

优先流量会导致地下水资源的快速污染。在具有相连的高渗透性地质结构的含水层中以及在海洋污染源无处不在的沿海系统中，尤其如此。我们考虑了由于火山岩含水层中的抽水造成的盐水入侵，熔岩管被表示为相连的高K结构，并比较了盐渍化响应与结构和等效均质系统不同的非均质含水层的响应。可变密度地下水流和盐分运移的三维模拟显示，熔岩流形成的导管在火山含水层中产生了优先的地下水流。这些管道使新鲜的地下水比其他系统更能向海上延伸。然而，相对于其他模型，陆上抽水导致盐水通过导管快速向陆地迁移，从而导致更严重的盐水入侵，特别是在浅水处。火山含水层中地质异质性的几何形状导致淡化地下水盐碱化的风险增加，并且由于盐水入侵的显着空间变化而导致大量不确定性。研究结果表明，在评估具有连通性高渗透性地质结构的火山岩和其他含水层中沿海淡水资源的脆弱性时，考虑地质异质性的重要性。火山含水层中地质异质性的几何形状导致淡化地下水盐碱化的风险增加，并且由于盐水入侵的显着空间变化而导致大量不确定性。研究结果表明，在评估具有连通性高渗透性地质结构的火山岩和其他含水层中沿海淡水资源的脆弱性时，考虑地质异质性的重要性。火山含水层中地质异质性的几何形状导致淡化地下水盐碱化的风险增加，并且由于盐水入侵的显着空间变化而导致大量不确定性。研究结果表明，在评估具有连通性高渗透性地质结构的火山岩和其他含水层中沿海淡水资源的脆弱性时，考虑地质异质性的重要性。