Barnard River rises on the eastern slopes of the Great Dividing Range, near Hanging Rock, east of Nundle, and flows generally east southeast, joined by seven tributaries including the Bank and Curricabark rivers, before reaching its confluence with the Manning River, near Bretti.

The river descends 1,240 metres (4,070 ft) over its 148 kilometres (92 mi) course.

The diversion involves the transfer of water from Orham Dam, impounded at Barnard Weir, and pumped over the Mount Royal Range and gravity fed into the Glenbawn Dam.

Water is accessed from the Barnard River to meet any shortfall from the Hunter River system in order to feed Plashett Dam and Lake Liddell, that are needed for the cooling of the Bayswater and Liddell electric power stations.

The scheme operates under a water licence issued by the NSW Government to Macquarie Generation.