Reservoir assessment using non-invasive geophysical techniques

This paper describes the use of three geophysical techniques to detect potential seepage that could jeopardise the integrity of reservoir embankments, could induce partial or total collapse and pose a risk to the population nearby. A fast scanning geophysical technique using two dipole electromagnetic (EM) profile apparatus GEM2 provided the first step to detect the weakest points on the selected dams in order to proceed to a more detailed analysis and visualisation of the soil erosion (fissuring or piping) using Electrical Resistivity Tomography (ERT). Finally, Self-Potential surveys were carried out to relate to the EM and ERT anomalies that could be pathways for seepage and changes of the water displacement inside the embankment. The three geophysical techniques used were evaluated in two case studies of reservoirs in locations relevant to flooding issues in Czech Republic. A risk approach based on the geophysical results was undertaken for the reservoirs embankments. The three techniques together were compared for the same problematic section and confirmed seepage by showing similar results. Conclusions were also drawn on the efficiency of using these three techniques as a package to give a comprehensive non-invasive assessment to be used as common practice by local authorities and Environment Agencies whereby remedial action could be recommended to protect assets and civilians