Mapping and monitoring saltwater intrusion are critical for the sustainable management of groundwater in coastal aquifers around the world. Increasingly, geophysical methods, such as electrical resistivity tomography (ERT), have been used to address these needs. We identify methods for the inversion of ERT data that would most accurately map the location and geometry of an intrusion wedge. This is accomplished using laboratory and synthetic experiments, with the classic representation of an intrusion wedge perpendicular to the coast. The laboratory experiments allow us to collect ERT data on a saltwater intrusion wedge in an environment in which we have supporting data that provided (1) the distribution of salinity within the tank with which to verify our inversion results, (2) the resistivity, porosity, and permeability of the porous medium, and (3) the transform between resistivity and salinity. The synthetic experiments allow exploration of issues of specific interest related to the presence of lithologic heterogeneity at a field site: the role of lithologic heterogeneity in introducing complexity into the resistivity-salinity relationship and the geometry of the saltwater intrusion wedge. We find that using a reference model with a good approximation of the wedge to inform the inversion greatly improves the ability of the resulting resistivity profile to map the wedge. Where there is no, or limited, lithologic heterogeneity, a parametric approach, which constrains the range of possible solutions by solving for a sharp interface between the saltwater and freshwater regions, is very effective at capturing the wedge location and geometry. Where there is lithologic heterogeneity, a hybrid between the parametric and informed inversion approaches is most effective, resolving the wedge with a high level of accuracy with little a priori information.

中文翻译：

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通过改进反演方法提高电阻率层析成像对盐水入侵成像的分辨率：实验室和数值研究

绘制和监测海水入侵对于全球沿海含水层地下水的可持续管理至关重要。越来越多的地球物理方法，例如电阻率断层扫描 (ERT)，已被用于解决这些需求。我们确定了可以最准确地映射入侵楔形的位置和几何形状的 ERT 数据反演方法。这是通过实验室和合成实验完成的，典型的入侵楔形垂直于海岸。实验室实验使我们能够在我们拥有支持数据的环境中收集盐水入侵楔的 ERT 数据，这些数据提供 (1) 罐内盐度的分布，用于验证我们的反演结果，(2) 电阻率、孔隙度，和多孔介质的渗透率，(3) 电阻率与盐度的转换。综合实验允许探索与现场存在的岩性非均质性相关的特定问题：岩性非均质性在将复杂性引入电阻率-盐度关系和盐水侵入楔的几何形状中的作用。我们发现使用具有良好楔形近似值的参考模型来通知反演极大地提高了所得电阻率剖面映射楔形的能力。在没有或有限的岩性非均质性的情况下，参数化方法通过求解咸水和淡水区域之间的尖锐界面来限制可能解决方案的范围，在捕获楔形位置和几何形状方面非常有效。存在岩性异质性的地方，