Most Illawarra beaches have remained good spots for swimming, despite a slight decline in water quality in the past year - although one is susceptible to faecal contamination.
Of the 21 swimming sites assessed in the latest State of the Beaches report, just one - a beach inside the entrance to Lake Illawarra - fell below the two highest grades of 'good' and 'very good'.
The NSW Department of Planning and Environment report for 2022-23 says the beach, partially enclosed by a breakwater, is graded as 'poor' because "microbial water quality is susceptible to faecal pollution, particularly after rainfall and occasionally during dry weather conditions".
It says this pollution potentially comes from stormwater and upstream sources in Lake Illawarra.
Monitoring at the beach revealed levels of the bacteria enterococci increased with higher rainfall and occasionally exceeded the safe swimming limit.
However, water quality was mostly good in dry conditions: 78 per cent of samples taken in dry weather when there had been no rain within 24 hours were within the safe limit.
The beach's location means it retains pollution longer and takes longer to recover from the impacts of stormwater.
Last year, the beach's suitability was rated as 'good'.
Overall, 95 per cent of swimming sites monitored were graded as 'good' or 'very good'.
"While this is a slight decline in performance on previous years, it reflects a very wet winter and spring, and some significant rainfall events associated with storms during summer," the report said.
Rainfall is the main driver of pollution to recreational swimming sites and the Illawarra experienced record-breaking rain in 2022 with multiple flooding events.
There were seven beaches in the region rated as having excellent water quality and suitable for swimming most of the time, earning them a grade of 'very good'.
These were Stanwell Park, Coledale, Austinmer, Woonona, Wollongong City, Fishermans and Shellharbour (north) beaches.
"Water quality at these beaches has been of a very high standard for many years and is suitable for swimming almost all of the time," the report said of the Wollongong beaches, while Shellharbour Beach's rating was consistent with previous years.
The remainder of the Illawarra's beaches were rated as 'good', with bacteria levels generally high after heavy rainfall.
Of the Wollongong beaches graded 'good' - Thirroul, Bulli, Bellambi, Corrimal, North Wollongong, Coniston and Port Kembla - the report said many had "several, or more significant, potential sources of pollution such as stormwater or upstream sources discharged from creeks or lagoons".
"We are fortunate in the Illawarra to be located so close to such a beautiful coastline," Heathcote MP Maryanne Stuart said.
People should generally avoid swimming at ocean beaches during and for at least one day after heavy rain, or if there are signs of pollution such as discoloured water or floating debris.
