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Role of geophysical surveys in the identification of water escape zones from retention lakes: a case study on a selected object in Upper Silesia

Mieszkowski R., Wójcik E., Kozłowski M., Popielski P.

Studia Quaternaria

2018

Vol. 35, Nr 2

121--129

The main scientific goal of this work is the presentation of the role of selected geophysical methods (Ground-Penetrating Radar GPR and Electrical Resistivity Tomography ERT) to identify water escape zones from retention reservoirs. The paper proposes a methodology of geophysical investigations for the identification of water escape zones from a retention fresh water lake (low mineralised water). The study was performed in a lake reservoir in Upper Silesia. Since a number of years the administrators of the lake have observed a decreasing water level, a phenomenon that is not related to the exploitation of the object. The analysed retention lake has a maximal depth between 6 and 10 m, depending on the season. It is located on Triassic carbonate rocks of the Muschelkalk facies. Geophysical surveys included measurements on the water surface using ground penetration radar (GPR) and electrical resistivity tomography (ERT) methods. The measurements were performed from watercrafts made of non-metal materials. The prospection reached a depth of about 1 to 5 m below the reservoir bottom. Due to large difficulties of conducting investigations in the lake, a fragment with an area of about 5,300 m2, where service activities and sealing works were already commenced, was selected for the geophysical survey. The scope of this work was: (1) field geophysical research (Ground-Penetrating Radar GPR and Electrical Resistivity Tomography ERT with geodesic service), (2) processing of the obtained geophysical research results, (3) modelling of GPR and ERT anomalies on a fractured water reservoir bottom, and (4) interpretation of the obtained results based on the modelled geophysical anomalies. The geophysical surveys allowed for distinguishing a zone with anomalous physical parameters in the area of the analysed part of the retention lake. ERT surveys have shown that the water escape zone from the reservoir was characterised by significantly decreased electrical resistivities. Diffraction hyperboles and a zone of wave attenuation were observed on the GPR images in the lake bottom within the water escape zone indicating cracks in the bottom of the water reservoir. The proposed methodology of geophysical surveys seems effective in solving untypical issues such as measurements on the water surface.

Ocena możliwości zastosowania metody georadarowej i elektrooporowej do identyfikacji rozluźnionych stref gruntów niespoistych

Mieszkowski R., Zawrzykraj P., Żmudzin D., Wójcik E., Popielski P.

Przegląd Geologiczny

2017

Vol. 65, nr 10/2

779--784

The results of the possibility of geophysical methods application (such as geoelectrical ones, including ground penetrating radar and electrical resistivity tomography) to identify areas of loose sands were presented in the article. Registered anomalies obtained from geophysical survey have been verified by geological and engineering tests (drillings and dynamic probing). Measurements were carried out along the part of the lateral earth dam, consisting of man-made soils with a thickness of approximately 7 m and underlying alluvial medium grained sands. The results obtained from the geophysical survey and direct assessment of density by means of dynamic probing allowed to demonstrate the relationship between a specific type of geophysical anomalies and the density of non-cohesive man-made soils.