River Murray general plan; locks and weirs

Set of navigation charts of the River Murray from Swan Reach to boundary of State, 153 to 405 3/4 miles from Murray mouth. Depths shown by soundings.

These River Murray charts were part of an extensive series of plans drawn up the Engineer-in chief of the South Australian Government early in the twentieth century. Plan 16 is a set of charts which shows water levels for determining positions of locks and weirs to be built along the River Murray to facilitate movement of shipping traffic and control water flows for irrigation. The plans are heavily annotated with details of plants and soil composition.

In the nineteenth century, paddle steamer trade peaked during the 1860s to the 1880s. Cargo to assist settlers was carried upstream and agricultural produce such as wool, wheat, animal hides and salt was carried back downstream. During this period between 200-300 boats were operating. Trade flourished and eventually railways were built to link lriver commerce with maritime ports. However low water at the end of summer was a major issue. Some paddle-steamers were left stranded as the rivers dried out beneath them. They had no option but to sit and wait for rain upriver to arrive and float them off. This was particularly noticeable during the 'Federation drought' of the late 1890s to 1902.

As a result, the states of South Australia, Victoria and New South Wales came together to discuss 'drought proofing' the river system. An agreement was finally reached in 1915 and the process of locking the river and managing its flow began. The locks were to assist river flows for irrigation purposes and for steam navigation. The River Murray Commission was set up to regulate water flow and oversee the building of water storage, locks and weirs. Six of these were built in South Australia in the 1920s and 1930s. At the Murray mouth, five barrages were constructed across Lake Alexandrina's inlets to stop seawater entering the system during times when the river was low.

The agreement was amended in 1924 because of dwindling steamer traffic, as the railways claimed the cargoes. Finally, it was decided in 1934 to further amend the agreement and only 14 locks rather than the original 26, would be built as the paddle steamer trade was dwindling. Paddle-steamers assisted in the construction by transporting rock, gravel and other supplies to the construction site.

In South Australia the first lock and weir was completed in 1922 at Blanchetown. In 1937, the last was completed at Euston in Victoria. The small locks on the barrages at the Murray mouth, Goolwa, were completed in 1940. In total, there are 13 navigation locks on River Murray weirs and two locks on the barrages at the Murray mouth.

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