The Swan River is a river in the south west of Western Australia. Its Aboriginal Noongar name is the Derbarl Yerrigan.Course of riverThe Swan River estuary flows through the city of Perth. Its lower reaches are relatively wide and deep, with few constrictions, while the upper reaches are usually quite narrow and shallow.The Swan River drains the Avon and coastal plain catchments, which have a total area of about 121,000 km2. It has three major tributaries, the Avon River, Canning River and Helena River. The latter two have dams (Canning Dam and Mundaring Weir) which provide a sizeable part of the potable water requirements for Perth and the regions surrounding. The Avon River contributes the majority of the freshwater flow. The climate of the catchment is Mediterranean, with mild wet winters, hot dry summers, and the associated highly seasonal rainfall and flow regime.The Avon rises near Yealering, 100 km southeast of Perth: it meanders north-northwest to Toodyay about 90 km northeast of Perth, then turns southwest in Walyunga National Park - at the confluence of the Wooroloo Brook, it becomes the Swan River.