This work is based on the assumption that a resistivity meter can effectively monitor water saturation in earth levees and can be used as a warning system when saturation exceeds the expected seasonal maxima. We performed time-lapse ERT measurements to assess the capability of this method to detect areas where seepage is critical. These measurements were also very useful to design a prototype monitoring system with remarkable savings by customizing the specifications according to field observations. The prototype consists of a remotely controlled low-power resistivity meter with a spread of 48 stainless steel 20 Ã\u97 20 cm plate electrodes buried at half-meter depth. We deployed the newly-designed permanent monitoring system on a critical levee segment. A weather station and an ultrasonic water level sensor were also installed in order to analyse the correlation of resistivity with temperature, rainfalls and water level seasonal variations. The preliminary analysis of the monitoring data shows that the resistivity maps follow a very reasonable trend related with the saturation/drying cycle of the levee caused by the seasonal variations of the water level in the irrigation channel. Sharp water level changes cause delayed and smooth resistivity variations. Rainfalls and, to a lesser extent, temperature seem to have an influence on the collected data but effects are apparently negligible beyond 1 m depth. The system is currently operating and results are continuously monitored.
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机译：这项工作基于这样的假设：电阻率仪可以有效地监控堤坝中的水饱和度，并且当饱和度超过预期的季节性最大值时可以用作预警系统。我们进行了延时ERT测量，以评估该方法检测渗漏至关重要的区域的能力。通过根据现场观察定制规格，这些测量对于设计原型监控系统非常有用，可节省大量成本。该原型包括一个远程控制的低功率电阻率仪，该电阻率仪分布在半米深度处，埋置了48个20 x 97厘米的20厘米厚不锈钢板电极。我们在关键的堤防段上部署了新设计的永久监控系统。还安装了一个气象站和一个超声波水位传感器，以分析电阻率与温度，降雨量和水位季节变化之间的关系。对监测数据的初步分析表明，电阻率图遵循一个非常合理的趋势，该趋势与灌溉渠道中水位的季节性变化引起的堤防的饱和/干燥周期有关。急剧的水位变化会导致电阻率变化延迟且平滑。降雨和较小程度的温度似乎对收集的数据有影响，但超过1 m深度的影响显然可以忽略不计。系统当前正在运行，并且结果将得到持续监控。
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