Avon River (Western Australia)

The Avon River is a river in Western Australia. It flows with a catchment area of in the state's Wheatbelt region. When the Avon reaches the Wooroloo Brook in the Walyunga National Park it becomes the Swan River, which flows through the Perth metropolitan area to its mouth at Fremantle Harbour.

Naming and terminology The Avon River and the Swan River are the same watercourse. By convention, the name "Avon" is used upstream of the confluence with the Wooroloo Brook in the Walyunga National Park, with the name "Swan" then used until the river mouth at Fremantle Harbour. This naming convention has been described as a "historical anomaly". For that reason, the main branch of the river system is sometimes referred to as the Swan–Avon River. Technical sources regard the Swan–Avon and Canning River as separate rivers flowing into a single body of water, the Swan–Canning Estuary, at Melville Water, rather than treating the Canning as a tributary of the Swan. This distinction was noted as early as 1827 by James Stirling.

Avon catchment area Lake Yealering in the Shire of Wickepin is the point of origin for the upper Avon River, and the catchment size above the confluence with the Salt River at Yenyening Lakes is .

The basin covers much of the Western Australian wheatbeltWestern Australia.(2008) Dept. of Water. Managing waterways in the Avon wheatbelt: field guide Perth, W.A. Dept. of Water – "This is an Avon Catchment Council project delivered by the Department of Water and funded with investment from the state and Australian governments through the Natural Heritage Trust and the National Action Plan for Salinity and Water Quality." "June 2008" http://henrietta.liswa.wa.gov.au/record=b2561801~S2 – Also available as an electronic version via the Internet. and extends beyond that in some areas near almost-always-dry Lake Moore in the northeast, water is received regularly from only the extreme western edge of the basin. Indeed, until an abnormally wet year in 1963 it was not realised that the northeastern part of the basin beyond Wongan Hills ever drained water into the river. Under present climatic conditions, it is almost impossible to produce runoff from anywhere outside the extreme west of the basin because the amount of rain required to fall before runoff would begin is as high or higher than the mean annual rainfall. The river has three main sub-catchments: catchments for the Mortlock, Yilgarn, and Lockhart rivers.

The river flows past County Peak, creating a picturesque view from the top.

Course and features Thirty creeks and rivers flow into the Avon; some of the larger tributaries include the Dale River, Brockman River, Mortlock River and the Mackie River. Most of these watercourses are ephemeral and only flow after rain in winter and spring.

Some permanent pools exist along the course of the river including Burlong Pool, Robins Pool, Long Pool, Cobblers Pool and Jimperding Pool.

The Avon River Valley is the third and final route for the Eastern Railway line through the Darling Scarp between Midland and Northam, having been constructed in the 1960s.

It is the site of an annual whitewater boating event, the Avon Descent.

Soils Due to the extraordinary age of the soils in the basin (which is on the extremely ancient Yilgarn craton), the rooting density of native flora is very high and its average specific discharge is probably the lowest of any basin of comparable size in the world. The extreme age of the soils also means that, at least after clearing for agriculture, almost all rivers in the basin have salinities above 0.3% (one-tenth that of the oceans and eight times that necessary to qualify as "fresh" water) and some much more than that.

Passing through some of the oldest settled European agricultural areas in Western Australia, the catchment area has extensive soil salinity issues, which have attracted governmental programmes to alleviate the loss of agricultural lands. Catchment groups that oversee projects in the tributary parts of the river have had considerable support and funding from commercial and non-governmental sources as well.

Avon River (Western Australia)

Bron en licentie