The river is sourced by three tributaries, the Sruh Croppa, the Aghinrawn and the Owenbrean, all of which sink into limestone on the Marlbank (a plateau on northern Cuilcagh Mountain) and join underground in the extensive Marble Arch cave system. The Sruh Croppa and Aghinrawn flow together for a short distance from Cradle Hole into Marble Arch Cave, before joining up with the Owenbrean at The Junction. In normal water levels, Marble Arch Caves tour begins by boat, underground on the initial stretch of the Cladagh, and passes The Junction before continuing upstream along the Owenbrean.