Efficient detection of mains water leaks using ground-penetrating radar (GPR)

Loss of water from urban water supplies is becoming an increasingly significant problem. Standard procedures for identifying and repairing a mains water leak can be time-consuming, disruptive and expensive. In association with Thames Water Utilities Ltd. the potential of GPR to accurately and efficiently detect mains water leaks has been investigated. The approach adopted here is to measure subsurface moisture conditions using GPR and from this locate the source of the leak. Common Mid-point velocity analyses for moisture measurement cannot be used since they are time-consuming. More direct methods have been employed utilising GPR parameters (such as trace mean, maximum and mini-mum amplitudes, amplitude and phase spectra and other waveform characteristics) measured in Reflection Profiling Mode. Knowledge of the effects of subsurface leakage moisture on the GPR return was used to map the location of a number of mains water leaks. A combination of amplitude techniques in the time and frequency domains was successful but is limited by substantial impact of other system components on the returned responses and by the depth of investigation. This neccessitates field calibration to correctly quantify soil moisture, otherwise the technique becomes a relative measure in which some dielectric patterns are not associated with the leak itself.