The Barrages are located in the channels linking the most downstream lake on the River Murray, Lake Alexandrina. Flow passes through the Barrages into the Coorong and out to sea through the Murray Mouth.
Before the barrages were built, tidal effects and the intrusion of seawater were felt up to 250 km upstream from the mouth of the River Murray during periods of low flow.
From the earliest days of settlement along the lower reaches of the river there were strong representations from landowners for the construction of barrages, primarily to keep the water fresh in the lower reaches of the River Murray, as well as Lake Albert and Lake Alexandrina.
In 1931, the Commission decided after an extensive investigation that five barrages be constructed. Work on the barrages commenced in 1935 and was completed in 1940. South Australia's Engineering and Water Supply Department undertook the works, with costs shared equally by the Governments of Victoria, New South Wales, South Australia and the Commonwealth.
The purposes of the barrages are to:
The River Murray is 2 530 km long but only 8 km of this is downstream of the Goolwa Barrage so the catchment of the barrages is almost the whole of the Murray-Darling Basin. All of the major tributaries of the River Murray join it further upstream than the barrages.