Innovative Dam Monitoring Tools Based on Distributed Temperature Measurement

Distributed fibreoptic measurements contain a number of particular features. Even though they are nowadays used for strain measurements, actually the most interesting parameter to be monitored by distributed fibreoptic measurements in dams is temperature. Due to their enormous mass, large structures such as dams usually show very slow behaviour in terms of temperature changes. It is well known that temperature measurements have to be carried out in concrete dams in order to observe the development of the heat of hydration. Furthermore, seepage flows affect the temperature field within the dams and their foundations. The Distributed Fibre Optic Temperature DFOT measurement was identified to be ideally suited for monitoring the temperature fields of dams, both for leakage detection and for the observation of concrete temperatures. For almost one decade, DFOT measurement has proven to be a powerful tool to detect and locate leakage in hydraulic structures. Leakage detection by means of DFOT measurements has been typically implemented through two major approaches: the gradient method, which employs the temperature as a tracer to detect anomalies in the flow field; and the heat-up method, which allows detecting the presence and movement of water by evaluating the thermal response after external heat is induced. In the past years more and more DFOT projects are under progress. As for today, the DFOT measurement has to be considered as a state of the art tool in dam monitoring. Nevertheless, especially in the field of leakage detection, there is still an enormous potential to improve effectiveness. New additional applications will be developed and important parameters as the seepage velocity in soil material will be measured with DFOT technology in the future. Being robust and gaining a high density of in-situ information out of the dam, DFOT technology has to be considered as one of the key technologies in tomorrow’s dam monitoring.