The
Murchison River is the second longest river in
Western AustraliaWestern Australia is a state of Australia, occupying the entire western third of the Australian continent. Australia's largest state and the second largest subnational entity in the world, it has 2.2 million inhabitants , 85% of whom live in the south-west corner of the state.The state's capital...
. It flows for about 780 km (490 miles) from the southern edge of the
Robinson RangesThe Robinson Ranges are a range of hills approximately north of Meekatharra in central Western Australia. The Range is a unique physographic feature located within the upper section of the of the Padbury group sequence in the Palaeoproterozoic basin...
to the
Indian OceanThe Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by South Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean...
at
KalbarriKalbarri is a coastal town in the Mid West region located 592 km north of Perth, Western Australia. The town is found at the mouth of the Murchison River and has an elevation of...
. It has a mean annual flow of about 200 million cubic metres.
The Murchison River arises on the southern slopes of the
Robinson RangesThe Robinson Ranges are a range of hills approximately north of Meekatharra in central Western Australia. The Range is a unique physographic feature located within the upper section of the of the Padbury group sequence in the Palaeoproterozoic basin...
, about 75 kilometres north of Meekatharra in central
Western AustraliaWestern Australia is a state of Australia, occupying the entire western third of the Australian continent. Australia's largest state and the second largest subnational entity in the world, it has 2.2 million inhabitants , 85% of whom live in the south-west corner of the state.The state's capital...
. From there it flows in a westerly direction for about 130 kilometres to its juncture with the
Yalgar RiverThe Yalgar River is a 142-kilometre-long tributary of the Murchison River, located in the Shire of Meekatharra in central Western Australia. It arises near the Great Northern Highway about 50 kilometres north of Meekatharra, flowing about 75 kilometres westward to a junction with its tributary, the...
, then west for another 100 kilometres before turning south-south-west for 120 kilometres, at which point it is joined by the Roderick River, about 30 kilometres east of the Murchison Settlement.
The
Murchison River is the second longest river in
Western AustraliaWestern Australia is a state of Australia, occupying the entire western third of the Australian continent. Australia's largest state and the second largest subnational entity in the world, it has 2.2 million inhabitants , 85% of whom live in the south-west corner of the state.The state's capital...
. It flows for about 780 km (490 miles) from the southern edge of the
Robinson RangesThe Robinson Ranges are a range of hills approximately north of Meekatharra in central Western Australia. The Range is a unique physographic feature located within the upper section of the of the Padbury group sequence in the Palaeoproterozoic basin...
to the
Indian OceanThe Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by South Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean...
at
KalbarriKalbarri is a coastal town in the Mid West region located 592 km north of Perth, Western Australia. The town is found at the mouth of the Murchison River and has an elevation of...
. It has a mean annual flow of about 200 million cubic metres.
Course
The Murchison River arises on the southern slopes of the
Robinson RangesThe Robinson Ranges are a range of hills approximately north of Meekatharra in central Western Australia. The Range is a unique physographic feature located within the upper section of the of the Padbury group sequence in the Palaeoproterozoic basin...
, about 75 kilometres north of Meekatharra in central
Western AustraliaWestern Australia is a state of Australia, occupying the entire western third of the Australian continent. Australia's largest state and the second largest subnational entity in the world, it has 2.2 million inhabitants , 85% of whom live in the south-west corner of the state.The state's capital...
. From there it flows in a westerly direction for about 130 kilometres to its juncture with the
Yalgar RiverThe Yalgar River is a 142-kilometre-long tributary of the Murchison River, located in the Shire of Meekatharra in central Western Australia. It arises near the Great Northern Highway about 50 kilometres north of Meekatharra, flowing about 75 kilometres westward to a junction with its tributary, the...
, then west for another 100 kilometres before turning south-south-west for 120 kilometres, at which point it is joined by the Roderick River, about 30 kilometres east of the Murchison Settlement. Another 70 kilometres to the south-south-west it meets its other important tributary, the Sanford River. Over the next 100 kilometres it makes a number of sharp turns, taking it about 70 kilometres to the west. It then flows to the southwest, passing under the
North West Coastal HighwayNorth West Coastal Highway in Western Australia is a generally north-south Western Australian highway which links the fishing town of Geraldton with the iron ore port of Port Hedland. It is long, and constructed as a sealed 2-lane single carriageway with overtaking lanes in some parts. It was...
at the Galena Bridge. Entering the
Kalbarri National ParkKalbarri is a national park in Western Australia of 1830.04 km
2, located 485 km north of Perth. The major geographical features of the park include the Murchison River gorge which runs for nearly 80 kilometres on the lower reaches of the Murchison River...
, it flows first to the north-west and then to the north, flowing through the Murchison Gorge, and passing through a number of tight bends known as the
Z BendThe Z Bend is a popular tourist lookout on the Murchison River Gorge in Western Australia. It is located at , about 30 kilometres east of Kalbarri, in the Kalbarri National Park. One of four lookouts in the national park, it is situated on a sharp bend in the gorge...
and The Loop respectively. It eventually turns to the south-west, passing through one more dogleg before disgorging itself into the
Indian OceanThe Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by South Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean...
at Kalbarri, the only settlement at any point along the river.
Murchison Gorge
Murchison Gorge is deep gorge in near pristine condition. It is popular with tourists, and there are a number of tourist lookouts. It is also of geological importance, as it exposes an excellent section through the
Tumblagooda SandstoneThe Tumblagooda sandstone is a geological formation deposited during the Silurian or Ordovician periods, around four to five hundred million years ago, and is now exposed on the west coast of Australia, straddling the boundary of the Carnarvon and Perth basins...
, a geological sequence rich in
OrdovicianThe Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian period and is followed by the Silurian period...
fossilFossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...
s.
Estuary
The final 18 kilometres of the Murchison River, from the Murchison House Ford to the mouth, are estuarine, and consist of a sequence of long sandbars and shallow pools mostly less than a metre deep. The estuary is permanently open to the sea, so is constantly affected by
tideTides are the rises and falls of sea level caused by the combined effect of rotation of the Earth and the gravitation of the Moon and the Sun. The tides occur with a period of approximately 12 and a half hours and are influenced by the shape of the near-shore bottom.Most coastal areas experience...
s and the inflow of saline sea water. When river flow is low, the estuary accumulates
sedimentSediment is any particulate matter that can be transported by fluid flow, and which eventually is deposited.Sediments are most often transported by water transported by wind and glaciers...
from the ocean, narrowing the river channel; this sediment is evacuated to the ocean during periods of high flow, but high flow also brings sediment into the estuary from upriver. Because of the high sediment load, and continual stirring by wind and river flow, the water is turbid.
The mouth of the estuary is a small
deltaA delta is a landform that is created at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
, closed by a sandbar except for a narrow channel. Although this channel is permanently open, it is usually very narrow and shallow, and so is now dredged every year to allow passage by
western rock lobsterPanulirus cygnus is a species of spiny lobster , found off the west coast of Australia. Panulirus cygnus is the basis of Australia's most valuable fishery, making up 20% of value of Australia's total fishing industry, and is identified as the western rock lobster.The species has five pairs of legs...
trawlers.
Basin
The Murchison River basin covers an area of about 82,000 km² in the
Mid West region of Western AustraliaThe Mid West region is one of the nine regions of Western Australia. It is located on the west coast of Western Australia, extending about 200 km north and south of its administrative centre of Geraldton. To the east it extends more than 800 km inland to Wiluna in the Gibson Desert...
. It extends about 550 km (340 miles) inland from the Indian Ocean, onto the Yilgarn Plateau. Rain generally only falls in the upper basin during summer cyclones, so for much of the year the Murchison River does not flow, having dry sandy river beds with occasional permanent pools.
The eastern reaches of the basin contain large chains of salt lakes, which flow only following rainfall. The drainage lines from these lakes merge to form the Murchison River about 90 km (60 miles) north north east of
MeekatharraMeekatharra is a town in the Mid West region of Western Australia. Meekatharra is an Australian Aboriginal word meaning 'place of little water'...
, near
Peak HillPeak Hill is the name of a goldfield, locality and the site of a gold mining ghost town in the Murchison Region of Western Australia. The gold mine covers 2,162 hectares and consists of four open-cut mines, titled Main, Jubilee, Fiveways and Harmony....
. From here the river flows west, then south west, then west to the Indian Ocean.
History
The Murchison River was named by the explorer
George GreySir George Grey, KCB was a soldier, explorer, Governor of South Australia, twice Governor of New Zealand, Governor of Cape Colony , Premier of New Zealand and a writer.-Early life and exploration:...
, who reached the river in 1839; the name honours the
ScottistScotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
geologistGeology is the science and study of the solid and liquid matter that constitutes the Earth. The field of geology encompasses the study of the composition, structure, physical properties, dynamics, and history of Earth materials, and the processes by which they are formed, moved, and changed...
Sir
Roderick MurchisonSir Roderick Impey Murchison, 1st Baronet KCB FRS was a British geologist who first described and investigated the Silurian system.- Early life and work :...
.
The estuary and river mouth was used as a holiday destination by families from the
GalenaGalena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...
mines in the 1920s and 1930s, and a military holiday camp was built there during
World War IIWorld War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...
. In 1951 the town of Kalbarri was gazetted at the river mouth, and by the end of the 1990s the population was about 2,000. In 1963 the
Kalbarri National ParkKalbarri is a national park in Western Australia of 1830.04 km
2, located 485 km north of Perth. The major geographical features of the park include the Murchison River gorge which runs for nearly 80 kilometres on the lower reaches of the Murchison River...
was gazetted, formally protecting the lower reaches of the river, including the gorge.
The
North West Coastal HighwayNorth West Coastal Highway in Western Australia is a generally north-south Western Australian highway which links the fishing town of Geraldton with the iron ore port of Port Hedland. It is long, and constructed as a sealed 2-lane single carriageway with overtaking lanes in some parts. It was...
passes over the river at Galena Bridge, which was opened by the Main Roads Department in December 1983
Further reading
- Curry, P.J. et al. (1994) An inventory and condition survey of the Murchison River catchment and surrounds, Western Australia. Department of Agriculture, Western Australia: Technical Bulletin Number 84. ISBN 0-7309-5998-8
- Western Australia. Dept. of Land Administration. Cartographic Services Branch.(1991) Land systems of the Murchison River catchment and surrounds : map series to accompany W.A. Department of Agriculture technical bulletin no. 84 Map Data: Scale 1:250,000 (E 115o10'--E 118o45'/S 25o—S 28o10').Notes: Land systems of the Murchison River catchment and surrounds by K.A. Leighton ... [et al.]. Date of survey: 1986-1988. Location maps:Belele, Byro, Cue, Glenburgh, Murgoo, Robinson Range.