Rivers, Floodplains and Wetlands

Rivers

A river can be described as a large natural stream of water flowing in a channel. Rivers can be characterised by flows of water, energy and materials such as sediment and nutrients. River systems are highly complex and often interactions between physical processes and biological conditions are poorly understood.

Most of the rivers in the Murray-Darling Basin flow over plains and many of these only carry water in times of flood. The Darling River, Murray River and the Murrumbidgee River are the three longest rivers in the Murray-Darling Basin and Australia.

Darling River

The Darling is the longest river in Australia measuring 2740 kilometres from its sources to its confluence with the Murray at Wentworth.

The main source of the Darling is usually considered to be the Severn, which becomes successively the Dumaresq, Macintyre, Barwon, and, finally, the Darling.

Discharge of the lower tributaries (Culgoa, Warrego, Paroo, Gwydir, Namoi, Macquarie, and Bogan) of the main stream fluctuates as a result of droughts and floods. Because much of the Darling's course runs through extensive saltbush pastures, receiving an average of less than 250 mm (10 in.) of rain annually, the river often loses more water by evaporation than is gained from its tributaries, many of which sometimes fail to reach the main stream.

Murray River

‘The River Murray is 2530 km long from the Snowy Mountains on the New South Wales - Victoria Border to the Southern Ocean in South Australia. The headwaters comprise less than 2 per cent of the Murray-Darling Basin, but contribute nearly 40 per cent of the inflow to the Murray River.

The flow in the Murray is very low by world standards. Its annual average flow would pass through the Amazon in less than a day. The Murray like the Darling also has a highly variable flow and in the early 1900’s constructions of locks and weirs began and the result is a more regulated river.

Murrumbidgee River

The Murrumbidgee River flows for 1,600 km and begins in the Kosciusko National Park in NSW. It plays host to 14 major dams and 8 large weirs. The Snowy Mountains Hydro Electric Scheme assists with regulating water flow and supplying the 10,000 kms of irrigation channels.

Floodplains

A floodplain is an area of relatively flat land covered by water during a major flood. It is built, layer upon layer, of nutrient-rich sediment deposited by the river during floods. This activity results in a complex of terraces, hollows, wetlands, billabongs, backwaters and anabranches.

Floodplains are a vital part of the river ecosystem. They are nature’s water treatment works, removing vast quantities of pollutants from inland river waters. They also act as a buffer zone, nursery and are the major centres of biological life in the river ecosystem.

Many floodplains are threatened within the Murray Darling Basin as they have been developed for agriculture, recreation and industrial purposes, thus dividing them from the river. Floodplains are also flooded less frequently and this has brought about changes in flora and fauna species that once thrived.

Wetlands

A wetland is defined as land that is inundated with shallow, slow moving or stationary water, on a temporary or permanent basis, that may be fresh, brackish or saline.

The major difference between a floodplain and a wetland is wetlands are permanently or temporality covered by water, whereas floodplains are only covered with water in times of floods.

The Murray-Darling Basin supports over 30 000 wetlands. Ten of these wetlands are of international significance and listed as Ramsar Wetlands. The Basin’s wetlands are among its most productive and biologically diverse ecosystems, providing the essential breeding and feeding habitats for many species of waterbirds, fish, invertebrates and plants.

Wetlands in the Murray-Darling Basin that are of international importance & listed under Ramsar Convention

State	Wetland	Area in ha
South Australia	1 Coorong and Lake Alexandrina and Albert	140 500
	2 Riverland, including Chowilla floodplain System	30 600
Victoria	3 Hattah-Kulkyne Lakes	1 018
	4 Lake Albacutya	10 700
	5 Kerang Lakes	9 172
	6 Gunbower Forest	19 450
	7 Barmah Forest	28 500
New South Wales	8 Macquarie Marshes Natural Reserve*	18 200
ACT	9 Ginini Flats, Namadgi National Park	125
Queensland	10 Currawinya Lakes National Park	151 300