Imaging Temporal Changes with Time-Lapse Seismic and GPR Methods – Rybnik Dam Survey

The Rybnik reservoir and its main dam, built in 1971, serve as a key element in power generation and flood mitigation. Over the years, the dam has faced multiple flood events, including the catastrophic 1997 flood. In 2024, it withstood southern Poland’s largest flood of the past decade. Two seismic campaigns were conducted in 2023 and 2024 to support dam monitoring. Both used 3C seismic acquisition geometries and were enhanced by Distributed Acoustic Sensing (DAS) and Spectral Ground Penetrating Radar (SGPR). Various fibre-optic cables, interrogators, and seismic sources, including sledgehammers and industrial sources, were tested in dense 5-meter spacing to develop a cost- and time-efficient methodology for dam investigation. The resulting dataset enables an innovative, high-resolution approach to monitoring structural conditions. SGPR proved critical for imaging the uppermost 8 meters, beyond the capability of seismic methods. The DAS and 3C data captured seasonal variations and revealed the underlying geological structure, including remnants of the original riverbed. These findings are particularly relevant for detecting water seepage beneath the dam, which must be monitored precisely. The work is crucial in the context of ageing hydrotechnical infrastructure and increasing environmental stressors.