281 Figure 4- Spatial and temporal temperature variations measured along the fiber-optic cable installed, showing (a) consistent seasonal temperature patterns along the monitored dam section and (b) a distinct 13 °C thermal anomaly over a ~100 m segment during relief-well pumping, corresponding to a known zone of historical seepage distress. Source: Wagner et al 2023 Strategically placed at dam embankment downstream, fibre optic cable through DTS detects real-time changes over large areas and distances. Seepage alters soil temperature, and fibre optic distributed sensing systems detect these changes precisely and frequently, providing continuous, real-time monitoring and providing a quantitative assessment on early signs of seepage occurring within the dam. 3.3 DSS/DAS strain-based deformation monitoring Rayliegh (DAS) and/or Brillouin (DSS) distributed sensing is used to detect spatial patterns of deformation including localised strain gradients associated with settlement, shear deformation, or crack initiation at lift interfaces, Figure 5. Unlike point sensors, distributed sensing along fiber optics provides a full spatial profile of strain over time, available in realtime, and allows for early detection of developing issues. A single fiber replaces hundreds of discrete sensors, reducing installation complexity and costs. [15][7][6].
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