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Australian rivers with regulated flows - the Murray-Darling, Snowy, Hunter, and Ord Rivers

Murray River downstream from Hume Weir

Murray River downstream from Hume Weir, 2007, courtesy of ABC

Most Australian rivers are located near the coast. Many of the largest and longest Australian rivers, found in the eastern part of the country, especially in the Murray–Darling Basin, have had their flows regulated by humans. In a massive engineering scheme, the waters of the Snowy River are diverted to the Murray River. In Northern Australia, the greatest diversion of water is on the Ord River around Kununurra, to provide water for irrigation and hydro-electric power.

In comparison, there are wild free flowing rivers in other parts of Australia such as the Daly, the Victoria, the Fitzroy and the Gascoyne in the north-west of Australia, the Oxley River in northern NSW and Queensland, and the Franklin in Tasmania. These wild rivers are free flowing heritage listed rivers which contain sites of international significance. There are also free flowing dry inland rivers, such as the Diamantina, which on occasions flows into Lake Eyre in northern South Australia.

The Snowy River Hydro Scheme at Talbingo

The Snowy River Hydro Scheme at Talbingo, NSW, courtesy of MDBA

The change to the flow of rivers has mostly occurred with dams and weirs. The damming of the Snowy River, for example, diverts water for use in farms, industry and day-to-day urban living. An irrigation system was introduced on the Murray River as early as 1887. However, these changes in water management have affected the flow and quality of water in the Murray–Darling and salinity is a major issue.

Salinity and changes to the water flow in rivers has affected the plants and wildlife. In the same period when irrigation was introduced in the Murray River, in the Hunter Valley, north of Sydney, there was extensive removal of most of the native vegetation surrounding the Hunter River. This led to erosion and, along with overgrazing and the building of levee banks, has dramatically affected the flow of the Hunter River and the natural river environment.

The management of Australia's regulated rivers is now negotiated as part of strategic plans to improve the river's health as well as balance the needs for other uses. The Australian Government measures the health of Australian rivers by their condition before European settlement. As part of collaboration between the federal, state and local governments, as well as catchment authorities, the Murray–Darling Basin Agreement aims to limit salinity in the Murray river and manages programs to ensure free passage by native fish.

Use of rivers – Indigenous and early European settler uses

The 'Yuki', 13 foot-long bark canoe made from a Red Gum tree by SA south east Aboriginal Communities

The 'Yuki', 13 foot-long bark canoe made from a Red Gum tree by SA south east Aboriginal Communities, courtesy of ABC

Aboriginal people who lived along the banks of rivers used them for many purposes. They fished and hunted and ate the plants that grew in the area. The land beside the rivers was used as campsites. Rivers were also used for transport and recreation by Aboriginal people.

There is evidence of Aboriginal occupation and use along the banks of many Australian rivers: burial sites, scarred trees whose bark was used to make canoes, and campsites. Aboriginal occupation on the Murray River goes back 40,000 years at Mungo National Park close by to the Murray River.

The early European settlers also used rivers as a transportation system as there were few roads. They used paddle steamers, especially on the Murray River, to transport people and essential supplies as settlements were established.

The paddle steamer Canberra on the Murray River near Echuca

The paddle steamer Canberra on the Murray River near Echuca, 2011 by Kathryn Wells

Paddle steamers were used to carry wool, wheat, and other goods up and down the river systems including the Murray, Darling and Murrumbidgee Rivers. Rivers were the inland highways of Australia until the introduction of railways in the 1850s, although paddle steamers continued on a commercial basis until the 1890s.

The first irrigation system on the Murray River was introduced in 1887 by Canadian George Chaffey. This reliable and convenient access to water greatly accelerated European settlement as well as the exploitation of the river's water supply around Mildura in Victoria and Renmark in South Australia.

Degraded condition of Australia's rivers in southern Australia

The health of Australian rivers is measured against their condition before European settlement. In the Australian 2011 State of Environment report, it was noted that

The use of this benchmark does not imply that we should restore inland water ecosystems to their near-original condition – it is simply the condition from which we measure change where we can….
State of the Environment 2011, Inland water , Current state and trends of the inland water environment


Salt affected irrigation channel

Salt affected irrigation channel, courtesy of MDBA

The introduction of European farming and water management techniques has had a dramatic effect on the Australian environment. The quality of available water in the Murray–Darling is a growing concern. Salinity is one of the most serious causes of water degradation facing Australia's rivers today.

Saline water in the Murray–Darling Basin filters down into underground aquifers and is a problem for agriculture, regional communities and infrastructure.

Water flow

The problem of more water being taken out of Australian rivers than is going into them has also created issues with flow. A river needs a certain amount of water to flow properly, to provide the right living conditions for animals and fish, and to provide enough water for plants.

The water flow through rivers determines much of the environmental condition of inland rivers. Of course, natural water flow varies according to season. Seasonal rain affects how long, how often and the amount of water that flows in a river. Large variations in river flow are typical in Australia and this can be greatly affected by drought and floods.

Hume Dam spilling at 40000 MLday

Hume Dam spilling at 40000 MLday, 2010 by Tony Crawford, courtesy of MDBA

Drought-breaking rains in the Murray–Darling and the south-east coast from May 2010 to May 2011 had a dramatic effect on the amount of water stored. The Murray–Darling went up from 28 per cent capacity to 80 per cent. The south-east coast catchment went up from 34 per cent capacity to 51 per cent. In comparison, with less rain, the south-west coast catchment went down from 38 per cent capacity to 21 per cent.

However, natural flows are mainly altered by people developing water resources, such as the building of dams and weirs. People have also diverted rivers, such as the Snowy River, built levees on floodplains, as with the Hunter River, and extracted groundwater from the water basins.

Murray Mouth and Coorong

Murray Mouth and Coorong, 2004 by Michael Bell, courtesy of MDBA

The development of water resources with dams and locks in the Murray–Darling division has caused major changes in the natural flow and flooding regimes. The natural flows support important floodplain wetland systems in the Murray–Darling Basin.

It has been calculated that the total flow at the Murray mouth has been reduced by 61 per cent due to humans altering and building water resources along the way:

Sediment and nutrients

The waters of Australian rivers are also being affected by the addition of certain substances, like sediment and nutrients.

Nutrients are substances, such as fertilisers used on crops, that make plants grow quickly. Nutrients can leak into a river system. Sometimes when there are too many nutrients in a river, an algal bloom will occur. An algal bloom is a large growth of a kind of microscopic plant called algae. When the algae in algal blooms eventually dies, it can kill the other kinds of plants and animals that live in the river.

Sediment occurs when dust and dirt resulting from erosion gets into the river water. Erosion is the natural wearing down of land caused by the weather. Removing trees and plants from an area can greatly increase the rate of erosion. Over grazing with large numbers of animals like sheep and cows can also contribute to erosion. More erosion means more sediment and rivers with high amounts of sediment can kill the plants and animals that live in them.

The silting up of the Hunter River floodplain and estuary

T R Brown, View of Hunters River, near Newcastle, New South Wales , 1812

T R Brown, View of Hunters River, near Newcastle, New South Wales , 1812, Copper engraving showing deltaic islands in mouth of river, SLNSW

The Hunter River catchment, north of Sydney, is one of the largest in New South Wales and reaches further inland than any other catchment. Originating in the Mount Royal Range, the river is approximately 300 km long, and enters the sea through its mouth at the port of Newcastle.

Before European settlement, the lower Hunter floodplain was covered with thick rainforest:

The riverbanks were covered with tall eucalypts and swamp oaks which often extended to the water's edge. Alternating strips of rainforest and naturally clear land across the floodplain, marked floodways and abandoned river channels.
Patterson Britton & Partners 1993 in NSW Department of Commerce, Manly Hydraulics Laboratory, Hunter Estuary Processes Study, 2003.
Nobby's Island and pier, 23 January 1820 by unknown artist,

Nobby's Island and pier, 23 January 1820 by unknown artist, Watercolour, SLNSW, DG SVIB/10

However, by the late 1830s, most of the cedar forest on the Plains was removed, the floodplain up to Singleton had been claimed by settlers and as a result, upstream of Maitland, the majority of rainforest had been removed. Whilst there was some riparian bank vegetation downstream of Oakhampton (near Maitland), levee banks began to be constructed in the late 1800s to protect and improve agricultural land. At this time it was one of the most populated parts of New South Wales.

Before Europeans arrived, the Awabakal clan of Muloobinba (Newcastle) who lived around the foreshore area and harbour entrance had good hunting and fishing facilities, and the area was popular for mud crabs and shellfish, as indicated by the large middens that have survived.

In 1855, at the mouth of the river, Rev L.E. Threlkeld wrote

Manual labour is now employed to fill up the space betwixt the Island and the main land so as to form a breakwater for the protection of the harbour at Newcastle, and a great part of the top of Nobby's Island has been taken down.
Coal River project, History

By 1900 the floodplain vegetation had mostly been removed and backwater lagoons or swamps had silted up to the point where they had become suitable for cultivation.

Newcastle in 1849, water colour by John Rae

Newcastle in 1849, water colour by John Rae (1813-1900), SLNSW

Dredging began in the 1840s, and was needed on a continuous basis from 1859. By the 1920s, the accumulation of the silt in the Hunter river mouth at Newcastle required dredging to allow access for ships. By 1951, the result of 20-years of dredging and reclaiming land resulted in the formation of a single land mass from what had been the deltaic islands of the lower Hunter.

From the 1950s, infrastructure and flood mitigation works continued, aimed at reducing flooding. The Lower Hunter Valley Flood Mitigation Scheme, begun in 1956, led to 160 km of levees and spillways, 140 km of farm drains, 200 floodgates, 30 km of river bank protection works and 40 km of control and diversion banks. This led to a substantial modification to the flow of the river and the shape of the riverbanks.

It was later realised that periodic flooding of rivers and their floodplains is a natural phenomenon which serves to provide water to underground aquifers and replenish layers of silty topsoil on the floodplain, essential for river life, plants and animals. If river channels do not flood then sedimentation occurs and if the river channel becomes narrow, as in the case of the Hunter, and then the energy of any future flood increases – causing further damage. In the 1955 flood, there was a large deposit of sediment over a major area from Oakhampton to Morpeth.

Following floods in the Hunter, salt enters the estuary at the river's mouth, and then, over a few months, is transported upstream against the river flow, especially during dry periods. Without proper flushing of the estuary, the water quality of the Hunter wetlands and lagoons is also affected by the lack of oxygen and an increase in algal blooms.

In the 1970s concerns were raised by the public about the pollution and the extent of industrial development in the Hunter estuary and, in the 1990s, the rehabilitation of the estuary wetlands commenced.

Plants in the Hunter estuary and wetlands include: mangroves, saltmarsh, common reed swamps, Casuarina glauca (she oak) and Melaleuca spp. (paperbark) stands and remnant forests. Riparian fauna includes fish and prawns but a relatively low number of frogs, reptiles and mammals. There are a relatively large number of threatened species. The Hunter estuary provides habitat for at least 23 threatened bird species, one amphibian, seven mammals and two floral species.

Irrigation and piped water from rivers

Morgan-Whyalla pipeline, South Australia

Morgan-Whyalla pipeline, South Australia, courtesy of MDBA

In the First National Survey of Water Use in Australia, 1981, over 74 per cent of water use was for irrigation compared to 8 per cent for other rural uses, 10 per cent for urban, commercial and domestic purposes and 8 per cent for industry and other activities. No other developed country uses such a high proportion of its water for irrigation and other rural uses.

Over two-thirds of river water for irrigation is used for pasture and cereal production whilst a small amount is used for fruit and vegetables. Irrigation can range from individual farmers pumping water from a stream to large private and government irrigation schemes which are found in all states, especially in the Murray Valley. However nearly all irrigation is dependent upon government-built and operated water storages. Over three quarters of these storages are in the Murray–Darling Basin.

Water piped from the Murray River supplies over 75 per cent of Adelaide's water in dry years. Other cities have also had to look to rivers further afield to supplement their water supplies. Melbourne draws on the Thomson River and Sydney on the Shoalhaven River. Industrial use of water is highly localised in centres such as Newcastle and the Hunter Valley, Sydney, Wollongong, Melbourne and Geelong.

Irrigation and hydro-electric power – The Snowy River

Snowy River, Illawong

Snowy River, Illawong, courtesy of NSW Office of Water

The Snowy River starts in the Australian Alps in New South Wales and is part of the Snowy River Basin area in south-east NSW . The Snowy is fed by one of the largest run-offs in Australia and is one of the largest snowmelt rivers in Australia. Its natural flow runs south until it reaches the ocean at Marlo in eastern Victoria. Along the way, it passes through the Snowy River National Park.

However the flow of the Snowy River is diverted, and only half of the Snowy's water reaches the ocean. The other half is diverted through a series of tunnels and pipes so that it flows into the Murray and Murrumbidgee rivers instead. This diverted water is used mainly for irrigation. As it flows toward the Murray and the Murrumbidgee, the water passes through a series of hydro-electric power stations, which generate electricity. The Snowy Mountains Hydro-electric Scheme was constructed by Australia's post war migrants as part of the changing face of Australia.

The alteration of natural river flows through the construction of dams and weirs, and erosion from land clearing, affect riverine health and contribute to water quality problems such as changes to water temperature. There has been a significant decline in the aquatic biodiversity of the Snowy below the town of Jindabyne where the river has been dammed.

At the same time, the Snowy River is identified as being of high conservation value. In October 2000, the NSW, Victorian and Australian Governments agreed to release environmental flows to the Snowy River in four stages to help preserve the water resources in river and groundwater systems.

The river has mythical status as part of early European history with Banjo Patterson's poem The Man from Snowy River telling the story of a man whose skill as a horse-rider allows him to ride through mountainside country to recapture an escaped horse.

Lower Ord system around Kununurra, Western Australia

The greatest diversion of water in Northern Australia occurs in the Lower Ord system around Kununurra, to provide water for irrigation and hydro-electric power.

The level of use of water diverted for irrigation is low, but hydropower demand can require release of more than half of all inflows to Lake Argyle. Of note, the creation of Lake Argyle and Lake Kununurra through regulation of the Ord River led to their listing as Wetlands of International Importance under the Ramsar Convention.
Northern Australia Land and Water, Science Review, full report, Water Resources in northern Australia , October 2009

The Murray–Darling River Basin

A river catchment is the area of land that surrounds a river and all of its tributaries, from the headwaters to the mouth. The river basin includes all the underwater aquifers and related springs. The Murray–Darling Basin measures over one million square kilometres, which is almost one-seventh of all the land in Australia. When measured from its source in Queensland to its mouth in South Australia, the Murray is over 2,500 kilometres long. The Murray River and its main tributary, the Darling River, are the two main rivers in the Murray–Darling River Basin. 

The Murrumbidgee

Aerial rice sowing in the Murrumbidgee Irrigation Area near Griffith, NSW, 1989

Aerial rice sowing in the Murrumbidgee Irrigation Area near Griffith, NSW, 1989. Image courtesy of the CSIRO Land and Water

Murrumbidgee means 'big river' in the local Aboriginal language. The Murrumbidgee is one of the largest and most significant tributaries of the Murray. It has one of the largest run-offs for water collected because of its sources located in the Australian Alps. It flows for 1485 kilometres from the Alps through the Australian Capital Territory (ACT) and then through the Riverina region of New South Wales to the point where it enters the Murray River.

The Riverina is one of Australia's most productive farming and agricultural areas. The farms in the Riverina area are reliant on the Murrumbidgee as a water source. In 2007, the Murrumbidgee Irrigation Area produced $800 million in farm produce.

The Murray River or Barmah

Little Rushy Swamp, Barmah Forest

Little Rushy Swamp, Barmah Forest

The first Europeans to encounter the Murray were Hamilton Hume and William Hovell, who explored the rivers west of the Great Dividing Range to see if they flowed into the ocean, or into a great inland sea. They named the river the Hume. However six years later, Captain Charles Sturt came upon the river and named it after Sir George Murray, not realising that it was the same river that Hume and Hovell had already named. Moreover, it was already known as Bama or Barmah by its Indigenous inhabitants, the home of a great living serpent.

The Murray River valley was transformed by clearing of native vegetation for the production of crops and livestock. Red gum forests along the rivers were felled for timber, burnt for firewood and cleared for farms and towns. Grazing by livestock along the river banks prevented regeneration.

The clearing ‘has allowed more rainfall to move down through the soil, filling the underground gravel and sand beds until they are now overflowing, forcing salty groundwater to the surface and into the River'. Irrigation enabled a massive increase in agricultural production but, at the same time, this increased waterlogging of the soil and salinization.

Aboriginal burial sites and midden areas have been flooded by dams. Levees have been built to keep the River in its channel and protect adjacent farms and towns. The wetlands and floodplain beyond the levees are now alienated from the River, reducing habitat for fish and waterfowl.
The Murray: A River Worth Saving

The Murray has also been important for recreation and tourism with the Murray being continuously navigable for 1986 kilometres from Goolwa to Yarrawonga. A prized fish, the Murray Cod can easily grow up to 1.8m in size and is much sought.

The Murray–Darling Basin Authority

Construction begins on the Hume Dam and Weir in 1919

Construction begins on the Hume Dam and Weir in 1919

Following the introduction of irrigation in 1887 and a succession of dry years from 1895 until 1902, three Premiers from NSW, Victoria and South Australia agreed in 1911 to appoint engineers to report and recommend on the use of water from the River Murray and its tributaries.

The River Murray Waters Agreement (later changed to The Murray–Darling Basin Agreement) was ratified in 1915 by the Australian and state governments by Acts, and proclaimed on 31 January 1917 by the Australian Government. The Agreement set out the shares of water available to each of the states, funding and construction of works, and a Commission to administer the provisions of the Agreement, know now as the Murray–Darling Basin Authority (MDBA).

Today, the Murray River has four major dams, 16 storage weirs and 14 navigable locks. The Authority has a responsibility to
  • promote the use and management of the Basin resources in a way that optimises economic, social and environmental outcomes
  • protect, restore and provide for the ecological values and ecosystem health of the Basin
  • ensure the return to environmentally sustainable levels of extraction of water resources.
    (Murray–Darling Basin Authority, Planning)

The Murray–Darling Basin Authority aims to mitigate salinity in the river through schemes that prevent saline groundwater from entering the River Murray. As part of improving the quality of the river, salt interception schemes pump saline water from underground aquifers and dispose of the salt by a process of evaporation and crystallisation.

The Authority also manages the Sea to Hume Fishway Program which aims to open up 2,100 km of the River Murray to free passage by native fish.

The Darling

The Darling River, which runs for approximately 1,545 kilometers, is Australia's second longest river. It starts in the north side of New South Wales and converges with the Murray River at Wentworth.

Darling River and the Brewarrina stone fish traps, Baiame's Ngunnhu

Baiame's Ngunnhu, stone fish traps on the Barwon River near Brewarrina, NSW

Baiame's Ngunnhu, stone fish traps on the Barwon River near Brewarrina, NSW, courtesy of Department of the Environment.

One of its tributaries, the Barwon River at Brewarrina, has one of the river's most significant features: its Aboriginal fish traps, known in the local Aboriginal language as Baiame's Ngunnhu. It is believed that Ngemba, Wonkamurra, Wailwan and Gomolaroi people have shared and maintained the traps for thousands of years. The traps are believed to be at least 40,000 years old, possibly the oldest surviving human-made structure in the world.

Consisting of river stones arranged to form small channels, the traps directed fish into small areas from which they could be readily plucked. The traps form a complex net of linked weirs and ponds along 500 metres of the river. They operate at varying water heights and can be altered to suit seasonal changes. Indigenous people use their expert knowledge of fish species and the environment to maximise their catch.

Brewarrina Ngemba Billabong has been declared a World Conservation Union (IUCN) Category V and VI protected area. It was declared an Indigenous Protected Area in November 2010. The ready availability of fish made Brewarrina one of the great inter-tribal meeting places of pre-European eastern Australia. The design of the traps however did not alter the flow of the river.

Ebb and flow

The questions about both the flow of a river and also the issue of preventing erosion upstream are a critical part of managing regulated rivers. How much flow is necessary for a river's health to combat salinity and algae needs to be balanced with how much water we need from dams for agricultural production. More questions about erosion, deforestation and the deposit of sediment are also considered in managing a regulated river to ensure that the river meets the needs for a sustainable future. Flows and floods are now understood to generate life through stimulating ecosystems. Ebb and flow is both the life of the river and its people.

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Last updated: 3 December 2015
Creators: Kathryn Wells

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