- Murchison River (Western Australia)
-
Murchison River Origin Robinson Ranges Mouth Indian Ocean, at Kalbarri Basin countries Australia Length 780 kilometres (485 mi) Source elevation 521 metres (1,709 ft)[1] Avg. discharge 193,500 ML/year [2] Basin area 82,000 square kilometres (31,660 sq mi) The Murchison River is the second longest river in Western Australia. It flows for about 780 km (480 mi) from the southern edge of the Robinson Ranges to the Indian Ocean at Kalbarri. It has a mean annual flow of about 200 million cubic metres.
Contents
Course
Location of the Murchison River
The Murchison River arises on the southern slopes of the Robinson Ranges, about 75 kilometres north of Meekatharra in central Western Australia. From there it flows in a westerly direction for about 130 kilometres to its juncture with the Yalgar River, 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 Highway at the Galena Bridge. Entering the Kalbarri National Park, 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 Bend and The Loop respectively. It eventually turns to the south-west, passing through one more dogleg before disgorging itself into the Indian 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 Sandstone, a geological sequence rich in Ordovician trace fossils.
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 tides and the inflow of saline sea water. When river flow is low, the estuary accumulates sediment 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.[3]
The mouth of the estuary is a small delta, 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 lobster fishing boats.[3]
Basin
The Murchison River basin covers an area of about 82,000 km² in the Mid West region of Western Australia. It extends about 550 km (340 mi) 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 (56 mi) north north east of Meekatharra, near Peak Hill. 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 Grey, who reached the river in 1839; the name honours the Scottist geologist Sir Roderick Murchison.
The estuary and river mouth was used as a holiday destination by families from the Galena mines in the 1920s and 1930s, and a military holiday camp was built there during World War II. 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 Park was gazetted, formally protecting the lower reaches of the river, including the gorge.[3]
The North West Coastal Highway passes over the river at Galena Bridge, which was opened by the Main Roads Department in December 1983 [4]
References
- ^ "Bonzle Digital Atlas - Map of Murchison River, WA". 2008. http://maps.bonzle.com/c/a?a=p&cmd=sp&zix=r&p=213505&st=&s=Murchison%20River&pg=1&m=0&c=1&x=114%2E22182&y=%2D27%2E633735&w=21233. Retrieved 2008-11-26.
- ^ "Department of Water -Water Resources Data - Murchison River, WA". 2008. http://kumina.water.wa.gov.au/waterinformation/wrdata/FLOW/702001/han.htm. Retrieved 2008-11-26.
- ^ a b c Brearley, Anne (2005). Ernest Hodgkin's Swanland: Estuaries and coastal lagoons of Southwestern Australia. University of Western Australia Press. pp. 262–271. ISBN 1-920694-38-2.
- ^ Edmonds, Leigh (1997), The vital link : a history of Main Roads Western Australia 1926-1996 Nedlands, W.A. : University of Western Australia Press. ISBN 1876268069. page 452
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.
Categories:- Rivers of Western Australia
- Mid West (Western Australia)
Wikimedia Foundation. 2010.
