the river tawe ( ) is a river in the south of wales. it flows in a principally southwesterly direction for some from its source below moel feity in the old red sandstone (black mountain) hills of the western brecon beacons to the bristol channel at swansea. its main tributaries are the right bank upper and lower clydach rivers and the afon twrch. the total area of the catchment is some 246 km (95 square miles).