The western side of the plateau is somewhat less rugged, and is drained towards the west by the tributaries of the Severn River, the Gwydir River and the Namoi River. These rivers form part of the Murray-Darling Basin. There are large dams at Copeton Dam on the Gwydir and at Keepit Dam, Chaffey Dam and Split Rock Dam in the Namoi catchment, plus Pindari Dam on the Severn River. The Nandewar Range is a major western spur of the highlands, culminating in Mount Kaputar near Narrabri.