Lower Lakes and barrages
In mid-January 2023, water levels in the northern regions of Lake Alexandrina peaked at 1.27 metres AHD, while water levels in Lake Albert peaked at 1.19 metres AHD. As the River Murray flood peak has now passed, water levels in the Lower Lakes are expected to slowly recede during February.
Prior to this event, and since the barrages were constructed in the 1930s, only the 1956 flood has been large enough to cause lake levels to rise significantly above normal levels. The 1956 flood had a peak flow of 341 GL/day in South Australia and resulted in a water level of 1.62 metres AHD at the Goolwa Ferry crossing.
Residents should be aware that short-term fluctuations in water level may still occur as a result of local weather events.
SA Water operates the barrages on behalf of the Murray-Darling Basin Authority and in consultation with the Department for Environment and Water. There are five separate barrages between Lake Alexandrina and the Murray mouth estuary, comprising a total of 593 openings that are controlled by either gates or stoplogs.
In addition, low-lying land on Ewe and Tauwitchere Islands can act as spillways when the water level in Lake Alexandrina exceeds 0.92 metres AHD, providing additional capacity to discharge flows from the Lower Lakes to the Murray Mouth.
All barrage gates have been open since early December 2022 to pass the floodwaters to the Coorong and ocean. High water levels in the Lower Lakes are a result of elevated water levels in the Coorong estuary.
Typically, water levels upstream of the five barrages on the Lake Alexandrina side of the structures have only been 1-2 cm higher than the water levels on the downstream (Coorong) side of the structures. This limits the volume of water released and keeps water levels high in the Lower Lakes.
During barrage flood operations, residents are advised that periods of saltwater ingress into the Lower Lakes may occur during storm events, but these periods are expected to be infrequent and short-lived.