Abstract: A reservoir is located in the north-central part of the Yunnan-Guizhou Plateau. The soluble rock in the reservoir area is widely distributed and the karst is developed. A nearly north-south trending fault in the middle of the reservoir area crosses both banks. To investigate the feasibility and sustainability of this reservoir, field surveys and geophysical explorations have been conducted in this area. Results suggest that the possibility of leakage to the adjacent low-lying valley is very small, to the south or downstream along the fault is also small. However, the reservoir will probably leak downstream and towards outside of the reservoir along the limestone erosion channel. The possibility of leakage to the dam downstream along the contact zone of the marble and gray-green rock or marble on the left bank is also small. Therefore, the normal water level of the reservoir may be sustained below the height of the Kc1 floor.