Fully Coupled Hydrogeophysical Inversion of Salt-Tracer Experiments

估计非均质含水层的水力导电性一直是地下水水力学的一个挑战。在控释实验中引入的盐羽的传播可以通过使用电流和电位电极的多种组合的延时电阻率层析成像（ERT）来监测。到目前为止，这些ERT数据的分析一直很繁琐，因为反演产生的浓度图像仍然需要在水力背景下进行解释。在之前的一个项目中，我们开发了一种完全耦合的水文地球物理反演方法，用于盐示踪剂试验期间获得的ERT数据。电信号的时间序列由它们的时间矩来表征。时间矩生成方程允许从流量和浓度矩方程中近似电信号的平均突破时间，而无需求解瞬态方程。将这些方程整合到地质统计反演方法中，从ERT数据推断水力导率分布。该方法已应用于人工生成的测试用例。在为期一年的扩展项目中，我们将在充填物日益复杂的准二维沙箱中进行一系列的盐示踪试验，利用时移ERT对试验进行监测，并利用全耦合水文地球物理反演方法反演其时间矩。我们将模拟瞬态浓度分布与推断的水力传导率场，并将其与实验中拍摄的图像进行比较。

Estimating hydraulic conductivity in heterogeneous aquifers remains a challenge of groundwater hydraulics. The propagation of salt plumes, introduced during controlled-release experiments, can be monitored by time-lapse electrical-resistivity tomography (ERT) using multiple combinations of current and potential electrodes. So far, the analysis of these ERT data has been cumbersome, because the inversion produces concentration images that still need to be interpreted in a hydraulic context. In a preceding project, we have developed a fully coupled hydrogeophysical inversion method for ERT data obtained during salt-tracer tests. The time series of electrical signals are characterized by their temporal moments. Temporal moment-generating equations allow approximating the mean breakthrough time of the electrical signal from flow and concentrationmoment equations without solving transient equations. These equations have been integrated into a geostatistical inversion method to infer the hydraulic-conductivity distribution from ERT data. The method has been applied to artificially generated test cases. Within the proposed one-year extension project, we will perform several series of salt-tracer tests in a quasi two-dimensional sandbox with increasingly complex fillings, monitor the experiments by time-lapse ERT, and invert their temporal moments with the fully coupled hydrogeophysical inversion method. We will simulate the transient concentration distributions with the inferred hydraulic conductivity fields and compare them to images taken during the experiments.