Fully coupled hydrogeophysical inversion of synthetic salt tracer experiments
Fully coupled hydrogeophysical inversion of synthetic salt tracer experiments
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DOI：
10.1029/2009wr008575
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发表时间：
2010-07
影响因子：
5.4
通讯作者：
Davina Pollock;O. Cirpka
中科院分区：
文献类型：
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作者：
Davina Pollock;O. Cirpka
我们提出了一种通过电阻率层析成像（ERT）监测盐示踪试验来确定水力传导率的方法。为了确保在反演中遵守流动，运输和地电的基本原则，我们使用电势扰动的时间矩进行完全耦合的水文地球物理分析。在预测模式中，我们使用矩生成方程和相应的伴随方程来评估灵敏度。对于反演，我们应用准线性地质统计反演方法。该方法在模拟实验室规模的准二维沙箱的合成案例研究中进行了测试，其中使用了48个电极和8个压力计。水力传导率场由电位扰动和水头的平均到达时间估计。估计的水力传导率场再现大多数功能，但是，损失的变化。即使只使用电信号的时间矩进行反演，也可以令人满意地恢复瞬态行为。此外，在真实和估计的情况下的浓度到达时间的空间模式是在良好的协议，使示踪剂羽流的传播可以相当准确地遵循。我们测试了大的测量误差和错误的先验信息对反演性能的影响。虽然先前的统计参数在检测水力传导率的主要模式中是次要的，但是大的测量误差可能对解决方案产生重要影响。此外，电极配置的选择似乎也很重要。特别是，严格基于地面的地电测量似乎不太适合通过ERT监测含水层内的盐示踪剂试验来确定导水率的空间模式。
We present a method for the determination of hydraulic conductivity from monitoring of salt tracer tests by electrical resistivity tomography (ERT). To ensure that the underlying principles of flow, transport, and geoelectrics are obeyed in the inversion, we perform a fully coupled hydrogeophysical analysis using temporal moments of electrical potential perturbations. In the predictive mode, we use moment‐generating equations with corresponding adjoint equations for the evaluation of sensitivities. For inversion, we apply the quasi‐linear geostatistical inversion approach. The method is tested in a synthetic case study mimicking a laboratory‐scale quasi two‐dimensional sandbox, in which 48 electrodes and 8 piezometers are used. The hydraulic conductivity field is estimated from the mean arrival times of electrical potential perturbations and hydraulic heads. The estimated hydraulic conductivity field reproduces most features with, however, a loss of variability. Even though only the temporal moments of the electrical signals are used for inversion, the transient behavior is satisfactorily recovered. Also, the spatial patterns of concentration arrival times in the true and estimated cases are in good agreement, so that the propagation of the tracer plume can be followed fairly accurately. We test the effects of large measurement errors and erroneous prior information on the performance of the inversion. While prior statistical parameters are of minor importance in detecting the major pattern of hydraulic conductivity, a large measurement error could have an important impact on the solution. Also, the choice of electrode configurations appears to be important. In particular, strictly surface‐based geoelectrical surveys do not seem to be very suitable for identifying spatial patterns of hydraulic conductivity by ERT monitoring of salt tracer tests within aquifers.