The construction of pumped-storage power stations has made significant progress in recent years. When selecting a reservoir site for such stations, gullies or depressions with natural reservoir basins are prior candidates. However, depressions in carbonate rock karst development areas exhibit characteristics such as karst erosion and vertical karst development. In such cases, understanding karst leakage is crucial for geological surveys related to such applications. The pumped-storage power station in Jiangyou presents highly complex karst development features and karst system. In this study, we investigate the karst hydrogeological features of the target area through water quality analysis and hydroxide isotope testing based on geological conditions. We studied the leakage conditions of the reservoir based on topographic and geological conditions, ground water distribution, water permeability of rock mass, and evolution trend of a relatively impermeable layer of the upper reservoir. Our findings provide geological references for selecting strategies to prevent reservoir leakage.