The quality of water entering Budgewoi Lake from Wallarah Creek declined from fair to poor during 2021-22 thanks to the flooding events.
For the fifth consecutive year, water quality for Ourimbah Creek remained fair.
And Canton Beach fell from Excellent to Fair in 2021-22.
These water quality measures come from the latest annual report of the Central Coast Waterways published by Central Coast Council and based on testing during the 2021-22 financial year.
The higher than average rainfall and floods contributed to an overall fall in water quality compared to last year.
But there were some good news areas.
Unlike other parts of Tuggerah Lakes, Lake Munmorah was significantly less affected by catchment flooding in March 2022.
Overall water quality within Wamberal Lagoon improved from fair to good in 2021-22.
The overall grade for Cockrone Lagoon returned to good in 2021-22.
But overall water quality within Terrigal Lagoon remained fair and Avoca Lagoon water quality decreased to fair in 2021-22 after its elevation to a good grade the previous year.
Overall water quality in Mangrove Creek remained good in 2021-22 but Patonga Ck, Mullet Ck and Mooney Mooney Ck grades dropped, as did Erina Ck and Narara Ck.
Cockle Bay and Booker Bay improved from good to excellent and Kincumber Creek improved from fair to good.
The Central Coast Waterways comes hot on the heels of the recently released Beach Watch annual report.
The Council’s waterways report covers water quality in more detail than the beach watch report and covers more areas.
Central Coast Council monitors the ecological health of its lakes, estuaries, rivers, creeks and lagoons to evaluate condition, and measure change and to target works to improve ecosystem health.
“A healthy waterway is one that supports natural processes, is resilient to change, can recover from human impacts and is relatively stable and sustainable through time,” Council says in the report.
“By reporting the monitoring results to the community each year, Council aims to raise awareness about the state of our waterways, and the pressures that affect ecological health.”
Council scientists measure turbidity, chlorophyll-a and seagrass depth range at each of the sampling sites. The report explains:
Turbidity is a measure of water clarity or cloudiness. Elevated turbidity is caused by more sand, silt, clay and microalgae suspended in the water. Long periods of high turbidity will negatively affect estuary health.
Chlorophyll-a is an indicator of levels of microalgae and nutrients in the water. High levels of chlorophyll-a indicate high inputs of nutrients which can lead to algal blooms and a decline in water quality.
Seagrass depth range is a biological indicator of water clarity over longer time periods. Seagrass grows slowly and depends on high water clarity, good access to sunlight and relatively low nutrient concentrations to survive and thrive.
See below for some details from the report or go direct to the report itself for all the details:
Southern Tuggerah Lake
Overall water quality in Ourimbah Creek remained fair for the fifth consecutive year.
One turbidity sample taken following the March 2022 flood was nine times higher than the trigger value.
Declines in overall water quality and ecological health were recorded at two sites, with the southern basin zone of Tuggerah Lake graded fair and the nearshore zone adjacent to Tumbi Creek graded poor in 2021-22.
“This was as a result of the chlorophyll-a exceeding its trigger value on multiple occasions with many exceedances being quite significant,” the report said.
“Despite these declines, seagrass depth range remained good within this area of Tuggerah Lake and Chittaway Bay also remained at an excellent overall water quality grade with no trigger value exceedances recorded for turbidity and only one exceedance for chlorophyll-a.”
Central Tuggerah Lake
Overall water quality flowing into Central Tuggerah Lake from Wyong River remained stable at a grading of fair.
Tuggerah Bay declined to fair and The Entrance declined to good.
Across all sites during 2021-22, turbidity exceedances were relatively minor, with none recorded at The Entrance.
When chlorophyll-a exceeded the trigger value, it was often by a substantial margin of up to three and a half times the trigger value.
“Again, this was in response to wetter than average conditions across all locations,” the report said.
Northern Tuggerah Lake
During 2021-22 overall water quality and ecological health remained good in the lake basin and at the Gorokan nearshore site. Canton Beach declined from excellent to fair, in response to regular minor exceedances of the trigger value and one large exceedance of the chlorophyll-a value in April 2022. This reading exceeded the trigger value by three and a half times showing the algal response to pulse inputs of nutrient and sediment during floods. Seagrass depth range for the northern zone of Tuggerah Lake remained good in 2021-22.
The water entering Budgewoi Lake from Wallarah Creek declined from fair to poor during 2021-22.
Following an East Coast Low and subsequent flooding in March 2022, turbidity was six times higher than the trigger value.
“Whilst floods are a natural occurrence, they can deliver a pulse of sediment and nutrients to the estuary which can negatively affect long-term estuary health when they occur on top of already elevated background levels,” the report stated.
Overall water quality and ecological health remained good in the basin, however the nearshore site at Lake Haven declined from excellent to fair in 2021-22.
Ecological health improved from fair to good at the nearshore site in Lake Munmorah and remained fair in the basin site during the 2021-22 sampling period.
Monitoring in Brisbane Water started in 2017-18.
Water quality throughout Brisbane Water in 2021-22 was graded between excellent and fair.
The ecological health grades of the three main basin sites, returned from good to excellent with no exceedances of either the turbidity or chlorophyll-a trigger values despite wetter than average conditions, the report stated.
Overall water quality and ecological health in Woy Woy Bay remained good in 2021-22.
Three southern bays of Lake Macquarie
For the fifth consecutive year, overall water quality and ecological health in the three southern bays of Lake Macquarie, Crangan Bay, Chain Valley Bay and Wyee Bay, remained excellent.