Water Leakage Detection Using Optical Fiber at the Peribonka Dam

A monitoring system based on temperature readings using fiber optic cables was designed for leakage detection through possible defects in the cutoff wall of the Peribonka main dam. The system is based on the heat pulse method to measure the apparent soil thermal resistivity. By combining a line heat source with a fiber optic distributed temperature measurement, local analysis of heat transfer can be performed to detect, locate and estimate the leak percolating velocity. Laboratory tests were carried out in clean granular sand having a hydraulic conductivity (k_Sat) of 10^–3 m/s. The apparent thermal resistivity measured with the system decreased from 0.6 m-K/W to negligible values when the Darcy velocity of the percolating fluid was increased from 10^–6 to 10^–4 m/s. This shows the capacity of the proposed system for detecting leakage in these kinds of soils. Finite element modeling of the experiments shows the same trend. Three hybrid cables were installed in boreholes through the alluvial foundation of the Peribonka main dam by way of boreholes. The cutoff wall is now completed and preliminary measurements indicate no significant seepage.