Seawater intrusion in fractured coastal aquifers: A preliminary numerical investigation using a fractured Henry problem
Seawater intrusion in fractured coastal aquifers: A preliminary numerical investigation using a fractured Henry problem
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DOI：
10.1016/j.advwatres.2015.09.013
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发表时间：
2015-11
影响因子：
4.7
通讯作者：
M. Sebben;A. Werner;T. Graf
中科院分区：
文献类型：
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作者：
M. Sebben;A. Werner;T. Graf
尽管裂缝性沿海含水层广泛存在，但之前的研究尚未探讨裂缝特征对海水入侵（SWI）的影响。这项研究首先使用数值模型来了解裂缝方向、位置和密度对理想沿海含水层中海水范围和地下水排放模式的影响。具体来说，使用 Henry SWI 基准问题的修改形式来研究包含单裂缝或规则间隔裂缝网络的含水层。测试了等效多孔介质 (EPM) 模型在 SWI 稳态模拟中表示简单裂缝网络的适用性。结果表明，裂缝对SWI的影响可能是混合的，从海水范围和混合区宽度的增强到减少。对于此处考虑的概念模型，与海水楔接触的垂直裂缝增加了混合区的宽度，而楔内陆的垂直裂缝对海水分布的影响最小。含水层下部的水平裂缝迫使楔向海洋，而位于淡水排放区域内的水平裂缝增强了楔。大致平行于海水-淡水界面的倾斜裂缝增加了海水向陆地延伸的范围，而垂直于界面的裂缝抑制了楔形。结果表明，EPM 模型可能不足以推断大多数裂缝情况下的盐度分布，尽管如果裂缝密度较高并且可以确定适当的分散性值，EPM 方法可能适用于正交裂缝网络。
Despite that fractured coastal aquifers are widespread, the influence of fracture characteristics on seawater intrusion (SWI) has not been explored in previous studies. This research uses numerical modelling in a first step towards understanding the influence of fracture orientation, location and density on the extent of seawater and accompanying patterns of groundwater discharge in an idealised coastal aquifer. Specifically, aquifers containing single fractures or networks of regularly spaced fractures are studied using modified forms of the Henry SWI benchmark problem. The applicability of equivalent porous media (EPM) models for representing simple fracture networks in steady-state simulations of SWI is tested. The results indicate that the influence of fractures on SWI is likely to be mixed, ranging from enhancement to reduction in seawater extent and the width of the mixing zone. For the conceptual models considered here, vertical fractures in contact with the seawater wedge increase the width of the mixing zone, whereas vertical fractures inland of the wedge have minimal impact on the seawater distribution. Horizontal fractures in the lower part of the aquifer force the wedge seaward, whereas horizontal fractures located within the zone of freshwater discharge enhance the wedge. Inclined fractures roughly parallel to the seawater-freshwater interface increase the landward extent of seawater and fractures perpendicular to the interface inhibit the wedge. The results show that EPM models are likely inadequate for inferring salinity distributions in most of the fractured cases, although the EPM approach may be suitable for orthogonal fracture networks if fracture density is high and appropriate dispersivity values can be determined.