Saturday, 1 December 2007

Never hurry a Murray!

Today's route has taken Mark from Murray Bridge to the southeastern extremity of a 145km sand bar which stretches along the coastline of South Australia where the River Murray joins the sea. It looks like there's some great physical geography there...

Murray Bridge, as its name suggests, is located at a road and rail crossing over the Murray River. And here, from a few hundred metres down stream, is a view of that rail bridge.

...and another aerial view of the surrounding land with some evidence of irrigation. The land to the right of the river is clearly watered by gravity-fed irrigation. The land on the left is probably higher and dependent on central pivot irrigation. We have seen this system of irrigation once before along Mark's route - in this posting in Iran The River Murray is here within 50km of the sea having travelled some 3750km from its source in the Australian Alps on the east of the continent. Despite its length, this is not a river which carries large volumes of water. In fact, on a few recorded occasions, it has completely dried up before reaching the sea. In order to avoid water shortages, the river has been subject to extensive water management schemes designed to regulate the flow in the river. Water is held back in the river's upper course by a series of dams which then release the water only in sufficient quantities to keep the river flowing and to meet the demands of agriculture, industry and domestic users.
The lack of an estuary means that shipping cannot enter the Murray from the sea. However in the 19th century the river used to support a substantial commercial trade using shallow-draft steamboats. Today, many paddleboats still ply the waters of the River Murray and it is possible (if you're not in a hurry!)to cruise the river on holiday or hire houseboats. A flavour of how the river is promoted can be gleaned by clicking the banner below.
The River Murray enters the sea in a most unspectacular way - firstly through the brackish Lake Alexandrina and then the Coorong lagoon before finding a narrow exit through the sand bar known as YoungHusband peninsula. After 3750km, it is actually dependent on a dredger working round the clock to keep the exit open!

The coastal features in this part of south Australia remind me of Chesil beach (below) and the Fleet lagoon though, if you thought that Chesil Beach at 27km was long, bear in mind that it is only one fifth the length of the Younghusband peninsula in South Australia. The processes which formed the two features are also different. While Chesil Beach probably formed as an off-shore bar which moved progressively on-shore and was then maintained through processes of longshore drift, Younghusband peninsula is what remains of a prehistoric dune system which was overcome by rising sea levels allowing salt water to penetrate inland forming the Coorong lagoon. Today the area is a National Park .

No comments: