DETECTION OF WATER LEAKAGE FROM DAMS BY SELF-POTENTIAL METHOD

A self-potential survey of streaming potentials along the eastern emba nkment of a dam was very successful in locating leakage areas and dete rmining the relative intensity of discharge. Self-potential measuremen ts have shown negative anomalies of up to 100 mV in amplitude. The wid th of the discharge areas ranged between about 40 m and 150 m. Repeate d observations of SP data at two different reservoir levels showed no great change in the leakage flow behaviour. Detailed mapping of SP val ues in the area revealed the possible presence of two sinkholes, the f irst with an estimated diameter of about 25-30 m and the second with a diameter of about 15 m based on a qualitative interpretation of the S P anomalies. The location of these two sinkholes coincides well with t he position of two subsurface normal faults in the area.