Abstract In coastal areas, geological heterogeneity influences the geometry and characteristics of the freshwater-saltwater mixing zone. Geophysical electrical and electromagnetic methods are increasingly used to delineate the freshwater-saltwater mixing zone or for groundwater model calibration. However, in practical applications, it is common when assessing pore water salinity from resistivity models to disregard the spatial variability of the aquifer properties assuming pore salinity is the dominant control on bulk electrical conductivity. In this paper we use a coupled hydrogeophysical model to assess the discrepancies in recovered salinity caused by the geophysical inversion and the application of the chosen petrophysical model when heterogeneity is ignored. We find that errors made when neglecting heterogeneity during petrophysical transformation are equivalent or higher in magnitude than inversion errors, more so when an inappropriate petrophysical model is used, but exhibit different spatial distribution. The results show that their combined effect results in significant overestimation of the spreading of the mixing zone. The analysis provides new insights to the groundwater community to better evaluate the reliability of geophysically-derived information when delineating the freshwater-saltwater interface or when geophysics is used quantitatively as part of model scenario simulation, uncertainty analysis or optimisation strategies.

中文翻译：

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从非均质沿海含水层的电阻率反演模型描绘盐水入侵时概念和计算错误的相对重要性

摘要 在沿海地区，地质异质性影响着淡水-咸水混合带的几何形状和特征。地球物理电气和电磁方法越来越多地用于描绘淡水-咸水混合区或用于地下水模型校准。然而，在实际应用中，在从电阻率模型评估孔隙水盐度时，通常假设孔隙盐度是对体电导率的主要控制，而忽略含水层特性的空间变异性。在本文中，我们使用耦合水文地球物理模型来评估地球物理反演引起的恢复盐度差异，以及在忽略非均质性时所选择的岩石物理模型的应用。我们发现在岩石物理转换过程中忽略非均质性时所产生的误差与反演误差相当或更高，当使用不合适的岩石物理模型时更是如此，但表现出不同的空间分布。结果表明，它们的组合效应导致对混合区扩展的显着高估。该分析为地下水界提供了新的见解，以便在描绘淡水-咸水界面时或在定量使用地球物理学作为模型情景模拟、不确定性分析或优化策略的一部分时，更好地评估地球物理衍生信息的可靠性。结果表明，它们的组合效应导致对混合区扩展的显着高估。该分析为地下水界提供了新的见解，以便在描绘淡水-咸水界面时或在定量使用地球物理学作为模型情景模拟、不确定性分析或优化策略的一部分时，更好地评估地球物理衍生信息的可靠性。结果表明，它们的组合效应导致对混合区扩展的显着高估。该分析为地下水界提供了新的见解，以便在描绘淡水-咸水界面时或在定量使用地球物理学作为模型情景模拟、不确定性分析或优化策略的一部分时，更好地评估地球物理衍生信息的可靠性。