Wookey Hole is on the southern escarpment of the Mendip Hills, and is the resurgence which drains the southern flanks of North Hill and Pen Hill. It is the second largest resurgence on Mendip, with an estimated catchment area of , and an average discharge of per second. Some of the water is allogenic in origin i.e. drained off non-limestone rocks, collecting as streams on the surface before sinking at or near the Lower Limestone Shale — Black Rock Limestone boundary, often through swallets such as Plantation Swallet near St Cuthbert's lead works between the Hunter's Lodge Inn and Priddy Pools. It then passes through major cave systems such as Swildon's Hole, Eastwater Cavern and St Cuthbert's Swallet, around Priddy, but 95% is water that has percolated directly into the limestone.