The Avon River is a river in Western Australia. A
tributary
A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainage ...
of the
Swan River, the Avon flows
[ from source to mouth, with a catchment area of .
]
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 West Australian wheatbelt 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
Wongan Hills is a range of low flat-topped hills in the Avon Wheatbelt bioregion of Western Australia. It is located at , in the Shire of Wongan–Ballidu.
History
The range was first recorded in 1836 by Surveyor General of Western Australia Jo ...
ever drained water into the river. Under present climatic conditions, it is almost impossible to produce runoff
Runoff, run-off or RUNOFF may refer to:
* RUNOFF, the first computer text-formatting program
* Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed
* Runoff or run-off, a stock market ...
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 Lockhart may refer to:
*Lockhart (surname)
Places
Australia
*Lockhart, New South Wales
*Lockhart River, Queensland
*Lockhart River, Western Australia
United States
*Lockhart, Alabama
*Lockhart, Florida
*Lockhart, Minnesota
*Lockhart, Sout ...
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
The Dale River is a perennial river located in the Wheatbelt region of Western Australia.
Rising on the eastern slopes of the Darling Scarp, the river flow generally east by north, joined by six major tributaries including the Dale River Sout ...
, Brockman River
The Brockman River is a perennial river located in the Wheatbelt region of Western Australia.
Course and features
The river rises north of Bindoon Hill and then flows generally in a southerly direction. The river is crossed by the Great North ...
, Mortlock River and the Mackie River.ephemeral
Ephemerality (from the Greek word , meaning 'lasting only one day') is the concept of things being transitory, existing only briefly. Academically, the term ephemeral constitutionally describes a diverse assortment of things and experiences, fr ...
and only flow after rain events 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
The Darling Scarp, also referred to as the Darling Range or Darling Ranges, is a low escarpment running north–south to the east of the Swan Coastal Plain and Perth, Western Australia. The escarpment extends generally north of Bindoon, to th ...
between Midland and Northam, having been constructed in the 1960s.
It is the site of an annual whitewater
Whitewater forms in a rapid context, in particular, when a river's gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that froths, making the water appear opaque and ...
boating event, the Avon Descent
The Avon Descent is an annual, two-day, white water event along the Avon and Swan Rivers in Western Australia. It includes both paddle craft (kayaks, surf skis) and small motor boats, and runs from Northam to the Perth suburb of Bayswater. It ...
.
Soils
Due to the extraordinary age of the soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
s in the basin (which is on the extremely ancient Yilgarn Craton
The Yilgarn Craton is a large craton that constitutes the bulk of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer Terrane have b ...
), the rooting density of native flora is very high and its average specific discharge 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
Soil salinity is the salt content in the soil; the process of increasing the salt content is known as salinization. Salts occur naturally within soils and water. Salination can be caused by natural processes such as mineral weathering or by the ...
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.
See also
* List of rivers in Western Australia
References
Further reading
* Harris, T. F. W. (1996) ''The Avon : an introduction'' Perth, W.A.: Water and Rivers Commission
External links
* http://www.wheatbeltnrm.org.au/ – formerly the ''Avon Catchment Council'' – known now as the ''Wheatbelt Natural Resource Management Inc.''
{{Authority control
Swan River (Western Australia)