Murray River Locks, Weirs and Barrages

Saturday, Mar 27, 2021 at 15:51

Stephen L (Clare) SA

The Murray - Darling catchment area in Australia covers the Murray and Darling Rivers systems and all their tributaries that extends from Queensland, most of inland New South Wales and all the way through South Australia. All this water after travelling many thousands of kilometres, will eventually enter the Southern Ocean through the Murray Mouth at Goolwa.

This River catchment area is the largest catchment area in Australia and covers an area of more than a million square kilometres and contains 22 major river catchment systems and is the twentieth largest river catchment system in the world.

Most people are aware that the length of the Murray River is over 2,500 kilometres, but few are aware that the Darling River area, which combines all the waterways of the Darling River above Bourke is over 2,700 kilometres in length.

At 10am on Monday 15 August 1853, Captain William Richard Randell departed Mannum on board Australia’s first steam driven paddle steamer, the PS Mary Ann and successfully and safely plied the Murray and Darling Rivers. The success of this journey then set the standards for future river boat trade, but with fluctuating river levels, there were times when paddle steamers became stranded for many years during droughts. With this new found inland water highway saw the growth of many towns along these waterways and for the first time in Australian history, large scale irrigation schemes were introduced during the 1880’s.

In 1887, Canadian brothers George and William Chaffey were invited to Australia by Victorian parliamentarian Alfred Deakin during a time of drought, where they established Mildura, followed by Renmark to become the first irrigation settlements in Australia. These towns prospered and grew and became the fruit bowl of Australia, but there was one problem that caused great concerns to the large irrigators, drought that was common to inland Australia and there were calls for all industries along these waterways to make some form of reliable water levels.

To ensure a reliable supply of water for irrigation and navigation, The River Murray Agreement Act of 1914 was passed by the Federal Government and by 1917 the River Murray Commission was established and saw the three states of New South Wales, Victoria and South Australia agreeing to the construction of 26 weirs and locks along the length of the Murray. Due to various reasons, only 14 were ever constructed which would then maintain all year round River levels for irrigation and safe navigation for over 1,600 kilometres, from the Murray Mouth near Goolwa to as far as Echuca in Victoria, and as far as Hay on the Murrumbidgee River in New South Wales.

By 1922, the first Lock and Weir was completed at Blanchetown and was officially known as Lock and Weir 1, but was named the William R Randell Lock, after Captain William Richard Randell, the first river boat captain to navigate the Murray River in 1853. It was also the Murray’s longest weir at 168.5 metres long while the last one to be completed was at Euston in 1937 near Robinvale in New South Wales, while the last weir to be completed without a lock was at Yarrawonga in 1939.

With the locks and weirs in place, it then established reliable pool levels between each lock, but it did not control the flow of water below lock 1 in Blanchetown in times of low river flows and drought. Sea water was entering the lower reaches of the Murray and Lower Lakes of the Coorong and as far as 250 kilometres upstream from the Murray Mouth.

In 1931, the then River Murray Commission decided that 5 Barrages needed to be constricted to improve the water quality of the lower Murray and Lower Lakes system. Between 1935 and 1940 5 baggages were constructed at Goolwa, Mundoo, Boundary Creek, Ewe Island and Tauwitchere. Of the 5 barrages, only Goolwa and Tauwitchere had locks constructed to provided access for fishing boats. The Barrages were built by the South Australian Engineering and Water Supply Department, with the costs shared equally by Governments of South Australia, Victoria and New South Wales. The success of the new barrages also increased the pool level between Goolwa and Lock 1 at Blanchetown by around 50 cm over a distance of 274 kilometres upstream.

The closure of the Murray Mouth has been ongoing well before European settlement with aboriginal Dreamtime stories of Ngurunderi walking across the area and the first European explorers to sail in this area in 1802 were Matthew Flinders and French explorer Nicolas Baudin and noted it was closed over. The next European explorer to venture here was Charles Sturt in 1830 and he also noted that the mouth was also filled with sand. Then in times of flood the mouth was washed open and so again this went on in history. The trouble now was more and more water was being pumped from the Murray which greatly effected the flows ever more and it was during the millennium drought that drastic action had to be undertake to save the delicate ecosystems of the lower lakes which were now choking.

In 2002 with the threat of the mouth closing over dredging of sand from the Murray Mouth, that involved dredging 24 hours a day for 8 years. In 2010 the drought was broken with higher flows of water and this kept the mouth open naturally. Low flows returned again in 2014 and in January 2015 dredging commenced again with 2 dredges located in the Goolwa and Tauwitchere channels. Maintaining an open Murray Mouth is the key objective of the Murray - Darling Basin Plan that was adopted in 2012 and today dredging is needed 95% of the time to keep the mouth open.
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