Swansea’s pristine waterway was tested alongside six other major tributaries in the 2017/18 period, with all but one receiving the highest possible overall grade. Cockle Creek in the south was the only zone to receive a B.

Lake Macquarie council’s manager for planning and sustainability, Alice Howe, said the millions of dollars invested into the estuares in the past seven years had shown considerable improvements in water quality, erosion prevention and the improvement of biodiversity.

“These range from rehabilitating wetlands in Cockle Creek to installing stormwater quality improvement devices (SQIDs) in the catchment,” she said.

“Our work with the development sector and local communities has also been critical to this achievement, as catchment runoff directly affects lake water quality.

“The latest results are a reminder of how our efforts as a community working together are having a very real and tangible positive effect on our environment.”

Howe also explained the sampling program now in effect would allow both long and short-term water quality variations to be assessed.

“Long term monitoring programs are essential for tracking estuary ecological health and to identify areas requiring management,” Dr Howe said.

The tests were carried out by contractors from the NSW Office of Environment and Heritage Estuaries and Catchments Team. Turbidity, the extent of seagrass beds and levels of chlorophyll-a – which in high concentrations usually indicates poor water quality – were used to gauge overall water quality.