 Just below Afon Dulyn the river is joined by Afon Melynllyn, a small river flowing from neighbouring Llyn Melynllyn.The river does not carry a great deal of water because water is transferred from Llyn Dulyn to the reservoirs of Llyn Eigiau and Llyn Cowlyd.Ceunant Dulyn, or the Dulyn Gorge, has been designated a Site of Special Scientific Interest (SSSI) since 1 January 1961 as a conservation measure to protect the site on account of its wildlife.