Commonwealth Environmental Water Office
South Australian Department of Environment and Water
JOINT MEDIA RELEASE
When it comes to getting the most out of water for the environment, it is all about timing. Whether it is to provide food for waterbirds, improve water quality or help native fish to spawn, getting environmental flows to the right place at the right time is critical.
Releasing water for the environment from the River Murray into the Coorong in South Australia has become a lot more sophisticated with the installation of automated gates on some of the barrages.
“Historically, releasing water through the barrages required staff to be onsite manually opening the gates. Now with remotely controlled gates at Tauwitchere and Ewe Island barrages, we can be much more responsive and release water at any time of the day,” said Jarrod Eaton, Water Delivery Manager at the South Australian Department for Environment and Water.
The automated gates save time and effort and incorporate decision support software that allows for more precise timing of water releases. Water for the environment can now be deployed when weather conditions are just right to harness tides and wind which can help target freshwater releases further down into the 110-kilometre Coorong wetland.
The gates are already proving to be immensely successful. Over summer low flows into the Coorong combined with hot, dry conditions saw salinity levels rise to unhealthy levels, threatening native plants, fish and waterbirds. In autumn, the gates were opened to let more water pass through to the Coorong, with releases timed for optimal conditions.
Salinity monitoring stations installed in the area clearly showed the released freshwater making the long journey down the narrow Coorong, pushed along by favourable winds, tides, and a seasonal rise in sea level that occurs naturally at this time of year.
The importance of freshwater flows to maintaining a healthy Coorong cannot be overstated.
“During the Millennium drought, the River Murray was disconnected from the Coorong for three years. With no freshwater flowing into the lagoon, salt levels rose to five times that of seawater” said Commonwealth Environmental Water Holder, Jody Swirepik.
“This was really devastating for the ecosystem, and some areas are still recovering even now. With carefully managed releases of water for the environment through the barrages we have been able to avoid a repeat of these conditions and provide a healthier environment for native fish and waterbirds,” she said.
Automated gates of the Tauwitchere barrage open. Photo: Geoff Gallasch
The science behind the story:
- The green line on the graph below shows salt levels in the northern Coorong from December 2019 to April 2020.
- During summer, salt in the Coorong reached levels higher than sea water due to low freshwater inflows from the River Murray, and high evaporation. In autumn, the barrage gates were opened to allow freshwater to flow into the Coorong, reducing salt levels and creating a healthier environment for native fish and waterbirds.
Graph showing salt levels in the northern Coorong from December 2019 to April 2020. The salinity of sea water is about 35 grams per litre. During summer, salinity rose well above that of sea water due to very low river flows and high summer evaporation. All barrages are closed and there were minimum flows from fishways only. In autumn, the barrage gates were opened. Salinity is falling to a healthy level as fresh water mixes into the Coorong. Low baseflows recommence and small 'pulses' during ideal conditions.