Application of hydrogeological and geophysical methods to delineate leakage pathways in an earth fill dam

Comprehensive field surveys, including various hydrogeological and geophysical methods, were carried out to appraise the applicability of those methods to a leakage problem at the Sandong earth fill dam in southwestern Korea. The methods applied in the field site were tracer tests, monitoring of drawdown and leakage with discharge of reservoir water, electrical resistivity surveys using the dipole-dipole array, self-potential (SP), and temperature logging methods. The leakage pattern in the reservoir wall was demonstrated by hydrogeological methods and was further clarified by the geophysical surveys. Leakage turned out to be through the right abutment of the reservoir wall. In this study, we confirmed that the electrical resistivity method is effective in detecting the zones favorable to leakage, and SP methods are useful for delineating the leakage pathways themselves, because leaks generate strong streaming-potential anomalies.