Temperature is used as a tracer since over 30 years to detect and monitor seepage in dams and water retaining structures [1]. Especially for efficient monitoring, experience from the last 25 years showed the great advantage of the use of distributed fibre optic temperature measurements (FO-DTS). Furthermore, by use of fibre optics not only temperature can be monitored permanently with a high spatial resolution, but also movement. Data is analysed and visualized in near real time on a Web platform to enhance the dam safety. The onset of leakages and movement can be detected at an early stage before causing potential hazards. Different monitoring techniques were developed and successfully implemented in different types of dams worldwide during the last decades. The technology has already been implemented as part of pilot projects in tailings storage facilities and has proved to became more and more a real asset in surveillance for these types of dams as well. This paper will elaborate on the method and applications for new and existing dams using case studies.