The high ground forms the catchment area for numerous rivers and streams. There are about of named rivers on Exmoor. The River Exe, from which Exmoor takes its name, rises at Exe Head near the village of Simonsbath, close to the Bristol Channel coast, but flows more or less directly due south, so that most of its length lies in Devon. The river and the Barle Valley are both designated as biological sites of Special Scientific Interest. Another tributary, the River Haddeo, flows from the Wimbleball Lake.