Electrical resistivity imaging for embankment seepage monitoring

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University of New Brunswick


Measurements of electrical resistivity variations are of special interest for non-invasive investigation of concentrated seepage through embankment dams . An experimental resistivity monitoring system is in development at the Mactaquac Hydroelectric Generating Station in New Brunswick, Canada. With 123 electrodes distributed over a 70 m x 25 m area adjacent to a concrete sluiceway structure, the system runs autonomously each night, collecting over 7000 apparent resistivity measurements. Annually the resistivity of water in the reservoir varied by nearly a factor of four, providing a strong signal for use as a tracer to highlight regions that appear to have experienced preferential water flow. Order-of-magnitude estimates for seepage flux are calculated by analyzing the time lag between resistivity changes measured in the reservoir and the dam core. The results suggest that the electrical resistivity imaging approach is feasible for seepage monitoring at water retaining structures, even in an electrically noisy environment.