The reservoir is located in the south of L County, J Province, in Tianmu Township, with a catchment area of 148.5km2, surrounded by mountains on three sides. The main reservoir irrigation area is within the contour line of less than 18m, reaching Pearl River in the east, Ganquan River in the north, Shimen Mountain, Changshan Mountain, Guilin Mountain and Caiqi Reservoir in the west, and Tianmu Reservoir site in the south. The terrain inclines from south to north. Tianmu River is the main stream in the basin