Black swans return in big numbers to the Coorong and Lower Lakes

Huge numbers of birds have flocked to South Australia’s Lower Lakes and Coorong region after months of sustained flows that have transformed the Murray mouth.

Sally Grundy lives on Mundoo Island Station, the last property on the Murray-Darling River; through the years she has seen the bust, and this year the boom in plants and wildlife.

“The increased water in the Coorong … has created an explosion of food web for many, many different species, but in particular the one that we have noticed dramatic changes in are the black swan,” she said.

Mundoo Island Station is home to three of the five barrages at the end of the river, meaning the property is bordered by salt water on one side and fresh water on the other.

“This summer, with the extraordinary water we’ve had around from the environmental flows and the rain, it has created an explosion on the saltwater side, so as far as your eye could see it was black swans and cygnets,” Mrs Grundy said.

There have also been large numbers of migratory birds from Siberia and all sorts of frogs and other wildlife spotted this year.

Since July, unregulated flow — water that is not a part of a controlled release — and the dams have been full, so water has made it all the way from one end of the basin to the other.

Adrienne Rumbelow from the SA Department for Environment and Water said that in the past eight months, large volumes of fresh water from the River Murray, supplemented with water for the environment, has helped raise water levels in both the Lower Lakes and Coorong.

It hasn’t happened for a number of years because although there have been larger flow events, like in 2016, they did not last as long.

“It was a short, sharp pulse; this one’s been pretty slow and steady and it’s built up through summer and it’s definitely been unusual.”

Lakes peaked in late December and early January around 0.84 metres AHD (at height datum).

“Lake Alexandrina is extremely fresh at the moment, so it’s around 300 to 400 electrical conductivity units, which is very fresh,” Ms Rumbelow said.

“We’ve also seen some reductions in Lake Albert and it’s been sitting pretty well below 1,500 EC, which is the freshest it has been for many years now.”

The Coorong, particularly the northern lagoon, has also been very fresh from the water coming over the barrages; there has also been some salinity reduction in the south lagoon but it remains rather salty.

Ms Rumbelow said the higher water level also increased the available plant food for water birds like the black swan.

“Black swans feed primarily on water plants in the Lower Lakes and Coorong, and the raised water levels have led to increased growth of water plants such as Tuberous rupture and other similar aquatic species,” she said.

Rick Hartman, Yarluwar‐Ruwe project coordinator from the Ngarrindjeri Aboriginal Corporation, said the increased numbers of kungari (black swan) cygnets was pleasing to see.

“It shows how ruwe (country) can respond with some additional water. This is a place of creation, where the fresh and salt water mix and our ngartjis need these waters to heal to enable their breeding.”