The Avon River in Western Australia winds approximately 240km, starting at a river in Wickepin in the State’s Great Southern agricultural region to Walyunga National Park in Upper Swan (Avon Valley). The river joins Wooroloo Brook in the National Park to eventually flow into the Swan River. The Avon River accounts for approximately 60% of the Swan River’s flow. The Avon River has a mean annual flow of 320 million cubic metres. The river experiences a multitude of changes as it flows towards the Swan River. From the flat, deep waters at Northam to the shallow, twisting rapids at Bells Falls. The river flows through the towns of Brookton, Beverley , York, Northam and Toodyay .

It is believed that the Avon River was once a freshwater river that flowed in the opposite direction and emptied into the Yenyenning Lakes near Brookton. The Avon River’s main environmental threat is siltation. The siltation problem began in the 1960s with the extensive clearing of natural vegetation for farming purposes. Topsoil washed into the river causing silt to build up. During the same time, bulldozers were used to clear islands in the river. The islands were thought to have been the main reason for floodings in the area. It was thought that by removing the islands it would increase the flow of the river and alleviate the blockages. Unfortunately, the decision resulted in larger siltation problems. The Avon River is the only breeding ground of the white swan in Australia. Northam has an extensive white swan breeding program. The river is also the location of the Avon Descent an annual whitewater boating event. Other main rivers in Western Australia are the Ord River, Blackwood River , Swan River and the Murchison River.