Impacts of River Regulation on the Terminal Lakes and Mouth of the River Murray,South Australia

The River Murray is a highly regulated, low gradient stream. Prior to barrage construction near the Murray Mouth saline water was present sporadically far upstream. Barrage completion by 1940 has had geo-morphic and ecological impacts. Estuarine Lakes Albert and Alexandrina became permanent freshwater bodies with elevated water levels. Exposed lake margins have eroded by up to 10 m yr', whereas along sheltered shorelines, sedimentation has accompanied reed growth. Upstream weirs have inhibited coarse sediment from reaching the lakes. In the Goolwa Channel, sedimentation changed from bioclas-tic sands to muds, accumulating at up to 4.5 mm yr' over the past 50 years. Regulation has also transformed a migrating flood tidal delta at the Murray Mouth into a permanently vegetated island.