ABSTRACT In this paper, we discuss the necessity of quantifying and correcting seasonal 3D effects on 2D electrical resistivity tomography (ERT) data measured along the embankments of rivers or artificial canals. A permanent ERT monitoring system has been continuously operating along the levee of an irrigation canal in Mantua province, Italy, since September 2015. To evaluate the importance of 3D effects and their dependence on seasonal variations, we first performed numerical simulations and also laboratory tests on downscaled levees of the study site. The results showed that 2D apparent resistivity pseudosections measured along the levee are significantly affected by 3D effects of the embankment geometry. Moreover, it was observed that 3D effects not only depend on the levee geometry, but they are also affected by seasonal fluctuations in the water level in the canal. This proved the importance of calculating 3D effects for the study site during dry and irrigation periods. Therefore, different synthetic models based on the levee geometry and water level in the canal in each period were constructed in RES2DMOD and RES3DMODx64 to quantify 3D effects for the study site. The ratios of apparent resistivity values calculated in RES3DMODx64 to the values calculated in RES2DMOD showed that 3D effects approach a maximum of 30% when the canal is empty during winter, and they arrive at a maximum of 10% when the canal is filled with water in summer. Using the graphs of the modelled 3D effects as a function of electrode spacing, apparent resistivity pseudosections measured by the permanent ERT system are corrected for 3D effects to obtain reliable resistivity sections after inversion. The final resistivity maps can be then converted into water content images using the empirical and site‐dependent relationship developed from core samples in the study area. Water content maps can be used to evaluate the stability of the levee and to detect possible seepage zones.

中文翻译：

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量化沿灌溉渠堤防的永久性电阻率断层扫描 (ERT) 监测系统的季节性 3D 效应

摘要 在本文中，我们讨论了量化和校正季节性 3D 对沿河堤或人工运河测量的 2D 电阻率断层扫描 (ERT) 数据的影响的必要性。自 2015 年 9 月以来，永久性 ERT 监测系统一直在意大利曼图亚省一条灌溉渠的堤坝上运行。为了评估 3D 效应的重要性及其对季节性变化的依赖性，我们首先对缩小研究地点的堤坝。结果表明，沿堤测量的 2D 视电阻率假截面受路堤几何形状的 3D 效应显着影响。此外，观察到 3D 效果不仅取决于堤坝的几何形状，但它们也受到运河水位季节性波动的影响。这证明了在干旱和灌溉期间计算研究地点的 3D 效果的重要性。因此，在 RES2DMOD 和 RES3DMODx64 中构建了基于每个时期运河堤坝几何形状和水位的不同合成模型，以量化研究地点的 3D 效果。RES3DMODx64 中计算的视电阻率值与 RES2DMOD 中计算的值的比率表明，3D 效应在冬季运河空时接近 30%，当运河充满水时，3D 效应达到最大值 10%。夏天。使用建模的 3D 效果图作为电极间距的函数，对永久 ERT 系统测量的视电阻率伪剖面进行 3D 效应校正，以便在反演后获得可靠的电阻率剖面。然后可以使用从研究区域的岩心样本开发的经验和站点相关关系将最终的电阻率图转换为含水量图像。含水量图可用于评估堤坝的稳定性并检测可能的渗流区。