The Murray River is a very regulated river system

In its natural state the Murray would be very different from the river seen today. In past years during long droughts the river ceased to flow and became a series of salty pools. In periods of flood it inundated vast areas of land causing damage to crops, stock, settlements and disruption to the river boat industry. At times of low water flow saltwater entered the river and sometimes extended up-river as far as Mannum.

For numerous years the states of South Australia, Victoria and New South Wales were unable to agree concerning the control and regulation of the  Murray River waters. In 1887 the question of river regulation was the subject of a Royal Commission.

• 1902 an interstate commission recommended the construction of storage weirs and a system of locks from Blanchetown to Wentworth.
• 1917 a River Murray Commission was formed.
• 1983 the scope of that commission was widened to consider water quality, recreation and environmental issues.
• 1988 the commission’s name changed to Murray-Darling Basin Commission.

A major responsibility of the Murray-Darling Basin Commission continues to be to control flows in the Murray in order to efficiently deliver to each state the amount of water to which it is entitled under the Murray-Darling Basin Agreement.

The water supply authorities of New South Wales, Victoria and South Australia operate and maintain the various structures of the Murray System for the commission.

Four main storages, 16 weirs and five barrages regulate the Murray. Thirteen of the weirs and two of the barrages have navigational locks. In 1931 the River Murray Commission recommended that five barrages be constructed. Work commenced in 1935 and was completed in 1940.

Goolwa Barrage is the largest of the structures. Stoplogs, located between the concrete piers, are removed or replaced to meet the conditions of flow and tide and so control the level of water in the lake. A lock chamber 30.5 x 6.1m allows craft to pass.

The Mundoo and Boundary Creek barrages are of the same general type as Goolwa, except that they are shorter and built in shallower water. There are no lock chambers.

Ewe Island and Tauwitchere barrages consist of concrete piers, steel radial gates and concrete stoplogs. Tauwitchere has a lock chamber 13.7 m x 3.8 m.

Weirs and locks serve three main purposes:

Year-round navigation was the primary purpose for weir and lock construction, making the river permanently navigable for a distance of 970km from the mouth. Each weir raises the level of water behind it by approximately 3.1 metres, to create a series of stepped pools from Blanchetown to Mildura.

Some weirs and locks, 12 to 14 between Mildura and Euston and 16 to 25 between Euston and Torrumbarry, were never built as the need for them ceased with the abandonment of the river boat trade.

Irrigation Weirs and Locks 1 to 5 in South Australia, Wentworth Weir, Lock 10, Mildura Weir, Lock 11, Euston Weir and Lock 15 all provide pools for irrigation by pumping. Torrumbarry Weir, Lock 26 and Yarrawonga Weir raise the level of the river to enable gravity diversion of water, via channels and natural waterways to large areas of land in Victoria and New South Wales.

Regulation Euston and Yarrawonga weirs act as minor storages for the ‘fine-tuning’ of river flows. Yarrawonga re-regulates water flushes from the Ovens and Kiewa rivers and is also operated, to a limited extent, for flood mitigation. During floods the weirs between Blanchetown and Torrumbarry can be almost dismantled and those at Mildura and at Torrumbarry withdrawn completely from the river.

Lake Victoria

Lake Victoria in New South Wales, performs the function of a balancing storage and helps ensure that water flow entitlements to South Australia are met. It is about 60 km west of Wentworth and downstream of the Murray-Darling junction. Kulkine Weir and Lock 9 raise the level of the Murray to allow diversion via Frenchmans Creek to the lake when required, water is released back to the Murray via Rufus River.

Menindee Lakes

Menindee Lakes on the lower Darling River in New South Wales consists of four main lakes of Wetherell, Pamamaroo, Menindee and Cawndilla. These also supply surplus water to the Murray System.

Hume Reservoir

Hume Reservoir Sited 16 km east of Albury the Hume is the main operating storage on the Murray System, storing water from the Upper Murray and Mitta Mitta rivers plus water transferred from the Snowy Mountains Scheme. Releases from the Hume maintain a minimum flow throughout the length of the Murray. In dry years additional releases are made specifically to meet South Australian requirements.

Dartmouth Reservoir

Dartmouth Reservoir on the Mitta Mitta River in north-east Victoria increases water supplies to the Murray System and provides a carryover storage to supplement the Hume in dry periods. Dartmouth is operated as a ‘storage of last resort’

The Snowy Mountains

The Snowy Mountains Scheme utilises the reliable water resources of the Snowy Mountains area for electricity generation and irrigation. The Snowy-Murray unit of the development involves the transfer of water from the Snowy River catchment, westward via a tunnel system under the Great Dividing Range to Geehi Reservoir. From Geehi water is diverted through Murray 1 and 2 power stations and into the Murray River via Khancoban Pondage and the Swampy Plain River. Lake Eucumbene provides the principal storage for the long-term regulation of the Snowy-Murray and Snowy-Tumut units of the scheme.