Dam leakage is a major challenge in karstic and metamorphosed karstic regions, where groundwater flow paths are difficult to identify due to complex geological conditions. This study evaluates the potential of dye tracing for investigating leakage from the Abbas Abad Dam, in west of Iran, which is founded on metamorphosed limestone and schist and experiences approximately 270 L/s of leakage under normal reservoir conditions was reported. Two fluorescent dye tracers were injected into two boreholes selected as potential leakage zones, and downstream water resources were monitored for 26 days using water sampling and activated charcoal collectors. No tracer was detected at downstream monitoring points. Subsequent drilling identified a highly permeable zone near borehole F24, approximately 75 m from CP301, where substantial grout loss occurred despite the injection of 5 tons of cement grout. Cement-grout injection subsequently provided field evidence of rapid hydraulic connection between the F24 zone and a downstream leakage outlet across the grout-curtain area. The first appearance occurred after 17 minutes downstream of the Dam in 70m distance that shows a high apparent velocity. The contrasting responses observed at CP301 and F24 demonstrate substantial spatial variability in hydraulic connectivity within the investigated foundation. These findings indicate that tracer detection is strongly dependent on the location of the injection point and its hydraulic connection with the preferential leakage pathway.