Geological Background--Hydrogeological Features
in the northwestern region of the geopark, the “s”-shaped karst area is surrounded by 100~400 m higher non-karst mountains which form a basin. the resulting large allogenic inputs converge in the bailang subterranean river system. the bailang subterranean river system is a featured by uniform karst aquifer and supply, runoff, discharge conditions and boundary conditions. its main stream runs south to north through the “s”-shaped karst area, controlling the development and location of the tiankengs and caves in the leye region.
hydrogeological conditions in the southeastern region of the geopark are similar to those in leye. allogenic water originating in the clastic area and precipitation in the karst area are the two main inputs to the poyue subterranean river system. the poyue has two main branches: qiaoyin subterranean river to the east and poxin subterranean river to the west. due to the local fault structure and surrounding sandy shale, the middle and upper reaches of the poxin subterranean river form an independent hydrogeological unit with exceptionally huge underground voids and karst windows.
the buliuhe river is located in the centre of the geopark, between the two blocky karst areas. the headwater flows through non-karst. in the geopark the buliuhe river cuts through a karst area, forming a deeply incised karst gorge.