Design and operation of the barrages
There are 5 barrages: Goolwa Barrage, Mundoo Barrage, Boundary Creek Barrage, Ewe Island and Tauwitchere Barrages. The water level upstream of the barrages is normally about .75 metres higher than mean sea level. The barrages cause an increase in water level of approximately 50 cm as far upstream as Lock 1 at Blanchetown (274 km upstream).
To control water levels, 'stoplogs' are typically used, particularly at the Goolwa Barrage. During periods of low river flow all the logs must be in place to completely stop the flow and maintain high lake levels. During floods, the stoplogs may all be removed. For intermediate flows, constant regulation is required to prevent the entry of salt water and to keep the water level upstream at the required level.
Goolwa Barrage is the deepest of the barrages. It is constructed on fine sand and silt, and is founded on timber piles and sheet piling up to 14 metres. The barrage contains a lock chamber 30.5 m by 6.1 m. The Goolwa Barrage is located 8 km upstream of the Murray Mouth.
Ewe Island and Tauwitchere Barrages are built on a calcareous reef, across wide and shallow channels. There are earth embankments at both ends. At Tauwitchere, a lock of 13.7 m by 3.8 m has been provided for the use of fishing boats.
The Mundoo Barrage and Boundary Creek Barrage are the shortest of the barrages. They are founded on a limestone reef. No provision was made in these barrages to allow the passage of shipping.
Associated with the barrages is the reclamation of 486 hectares made to the Sir Richard Peninsula, to the west of the barrages. The purpose of this reclamation was to minimise sand drift entering the river between the barrages and the river mouth, and to maintain the protecting peninsula between the Goolwa Barrage and the sea.