More than 570 operational bays across the five barrages — Goolwa, Mundoo, Boundary Creek, Ewe Island and Tauwitchere — have been opened because of the high volume of water in the river flowing to the Lower Lakes, Coorong and Murray Mouth.
It is believed to be the most significant barrage opening since the 1970s. About 400 of the barrage bays were opened during a high-flow event when the millennium drought broke in 2010-11.
South Australia’s Engineering and Water Supply Department built the barrages in the 1940s to maintain water levels and water quality in the Lower Murray, with the costs of construction shared between South Australia, NSW, Victoria and the Commonwealth.
The Murray-Darling Basin Authority’s river management executive director Andrew Reynolds said while the 2022 flooding had left many basin communities and businesses seriously impacted, it presented an opportunity to deliver unregulated flows through the river system to the sea.
The opening of the barrages follows the removal of each weir in the river all the way to Yarrawonga, almost 2000 kilometres upstream.
“Our thoughts are with those suffering as a result of the flooding,” Mr Reynolds said.
“It has been a long time since the complete opening of all barrage bays, and logistically it has been an enormous exercise as only a small number of the bays are automated.
“Most of the barrages were opened onsite by SA Water using specialist equipment.”
In dry years of low water availability, barrage releases are limited and are supported by environmental water recovered under the Murray-Darling Basin Plan.
In wet years, the barrage gates are opened to reinstate continuous connectivity between lakes Alexandrina and Albert and the Coorong.
A utility vehicle with a crane on the back lifts concrete stop logs out of a barrage, allowing water to flow between the Lower Lakes and Coorong areas.
“We have been able to stop the dredging of sand at the Murray Mouth,” Mr Reynolds said.
“The flows through the barrages are helping to make the mouth much wider and deeper, and we’re hopeful that as a result of this scouring event we may not have to dredge the mouth for several years.
“Floodplain vegetation that hasn’t had a drink for a long time is now being watered — some for the first time since the 1970s.
“Black box trees and river red gums at the margins of floodplains that have been struggling in recent years are now getting a life-saving drink that will set them up for the years ahead.
“This is also flushing a lot of salt out of the system, which is an important objective under the Murray-Darling Basin Plan to improve long-term water quality.”
