Electrical resistivity imaging for investigation of seepage paths in the Yukari Gökdere Dam, Isparta, Turkey

Upon completion of the Yukari Gokdere Dam, designed as a clay-cored rock fill dam for irrigation purpose, in Egirdir district of Isparta, the water started to accumulate in the reservoir. Following this, reservoir’s water level has dropped sharply, and it was completely empty. In the winter season, the dam has accumulated water again; however, two water leakage areas were observed on the downstream side of the dam. Three different survey data were utilized to investigate the seepage paths of the dam. The first data set, before the construction phase, involves the lithological units and rock quality designation indexes in the cores recovered from boreholes, and the in-situ ground water table characteristics and Lugeon’s tests applied in the boreholes. The second data set, electrical resistivity, was collected in three campaigns performed in June 2017, August 2017, and February 2018. Resistivity data were measured using dipole-dipole electrode array with electrode spacing of 1.7 m and 2.5 m in the reservoir, and 3 m on the crest. The last data set includes benchmark readings. With the evaluation of resistivity, geotechnical, and survey data, the leakage in the dam is interpreted to be due to damaged parts in the clay fill material forming the main body of the dam.