Murray River

The Murray River (River Murray in South Australia) is Australia's longest river. At 2,995 kilometres (1,861 mi) in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between the states of New South Wales and Victoria as it flows to the northwest, before turning south for its final 500 kilometres (310 mi) or so into South Australia, reaching the ocean at Lake Alexandrina. The water of the Murray flows through several lakes that fluctuate in salinity (and were often fresh until recent decades) including Lake Alexandrina and The Coorong before emptying through the Murray Mouth into the southeastern portion of the Indian Ocean, often referenced on Australian maps as the Southern Ocean, near Goolwa. Despite discharging considerable volumes of water at times, particularly before the advent of large scale river regulation, the Mouth has always been comparatively small and shallow. As of 2010, the Murray River system receives 58% of its natural flow. It is perhaps Australia's most important irrigated region and is widely known as the food bowl of the nation.

The first Europeans to encounter the river were Hamilton Hume and William Hovell, who crossed the river where Albury now stands in 1824: Hume named it the Hume River after his father. In 1830 Captain Charles Sturt reached the river after travelling down its tributary the Murrumbidgee River and named it the Murray River in honour of the then British Secretary of State for War and the Colonies, Sir George Murray, not realising it was the same river that Hume and Hovell had encountered further upstream. Sturt continued down the remaining length of the Murray to finally reach Lake Alexandrina and the river's mouth. The area of the Murray Mouth was explored more thoroughly by Captain Collet Barker in 1831. In 1852 Francis Cadell, in preparation for the launch of his steamer service, explored the river in a canvas boat, travelling 1,300 miles (2,100 km) downstream from Swan Hill. In 1858 the Government Zoologist, William Blandowski, along with Gerard Krefft, explored the lower reaches of the Murray and Darling rivers, compiling a list of birds and mammals.

In 1915 the three Murray states — New South Wales, Victoria and South Australia — signed the River Murray Agreement which proposed the construction of storage reservoirs in the river's headwaters as well as at Lake Victoria near the South Australian border. Along the intervening stretch of the river a series of locks and weirs were built. These were originally proposed to support navigation even in times of low water, but river-borne transport was already declining due to improved road and rail systems. Lock 1 was completed near Blanchetown in 1922. Torrumbarry Weir downstream of Echuca began operating in December 1923. Of the numerous locks that were proposed, only thirteen were completed; Locks 1 to 11 on the stretch downstream of Mildura, Lock 15 at Euston and Lock 26 at Torrumbarry. Construction of the remaining weirs purely for navigation purposes was abandoned in 1934. The last lock to be completed was Lock 15, in 1937. Lock 11, just downstream of Mildura, creates a 100-kilometre long lock pool which aided irrigation pumping from Mildura and Red Cliffs.

Each lock has a navigable passage next to it through the weir, which is opened during periods of high river flow, when there is too much water for the lock. The weirs can be completely removed, and the locks completely covered by water during flood conditions. Lock 11 is unique in that the lock was built inside a bend of the river, with the weir in the bend itself. A Channel was dug to the lock, creating an island between it and the weir. The weir is also of a different design, being dragged out of the river during high flow, rather than lifted out.

Source: wikipedia