Flow-field fitting method applied to the detection of leakages in the concrete gravity dam

Water leakage detection in concrete gravity dams is an important task for surface freshwater resources applications and management. The Flow-Field Fitting (FFF) method aims to detect leakage inlets and determine leakage pathways. The approach consists in injecting current between two electrodes upstream and downstream, to generate a relatively steady current field. As a result, the current density will be higher in a location where leakage occurs. Thus, we can find out leakage inlets using the current density distribution recorded in water reservoirs. A case study was conducted to test the performance of the FFF method. To verify the correctness of the method in the concrete gravity dam, we use numerical simulations, acoustic logging, temperature tracer, borehole television, and water pressure test to an existing dam in China. Numerical results show that an appropriate selection of the background value of current density and the grid space of detection is more important, which can reflect the size, shape, and location of leakage inlets. At the leakage location, four invasive approaches were mutually confirmed and were relatively consistent. These integrated results show that the FFF method is helpful to localize leakages. In addition, data obtained by the FFF method do not need to be inverted. This study shows that the FFF method can provide a rapid and practical approach to detecting leakages in concrete gravity dams. The detection results can serve as an engineering basis for leakage management. The FFF method can also be applied to investigate other types of dam leakages.