Swimming conditions in this website are predicted from the likelihood of bacterial contamination at typical recreational sites based on correlations with salinity levels as a proxy for rainfall and pollutants runoff. Swimming sites could also be affected by harmful algae blooms which would not be informed through this website. For further information on the presence of harmful algae blooms visit Hornsby Water Quality or call Water NSW algae hotline 1800 999 457.
Pollution is unlikely, enjoy your swim!
Pollution is possible, take care
Pollution is likely, avoid swimming today
(average last 24 hours, parts per 1000)
|Bar Island||27.9||25 May 18:15|
|Bennetts Bay||27.2||25 May 18:15|
|Brooklyn Baths||33.7||25 May 22:15|
|Calabash Bay||26.6||25 May 21:45|
|Courangra Point||23.3||25 May 18:15|
|Crosslands Reserve||19.9||25 May 06:15|
|Dangar Island||33.9||25 May 22:15|
|Deadhorse Bay||33||25 May 22:15|
|Gunyah Point||34||25 May 22:15|
|Laughtondale||11.3||26 May 00:00|
|Milsons Passage||30.6||25 May 18:15|
|Sandbrook Inlet||30||25 May 18:15|
|Twin Beaches||27.9||25 May 18:15|
Swimming conditions are predicted from the likelihood of bacterial contamination based on recorded salinity levels as a proxy for rainfall and pollutants runoff. The following steps are undertaken in the calculation of swimming conditions:
|Crosslands Reserve||Pollution is unlikely, enjoy your swim! = Salinity is more than 18 ppt|
Pollution is possible, take care = Salinity between 12 and 18 ppt
Pollution is likely, avoid swimming today = Salinity is less than or equal to 12 ppt
|Courangra Point & Laughtondale||Thresholds are based on the historical 30th and 10th salinity percentiles|
|All other locations||Pollution is unlikely, enjoy your swim! = Salinity is more than 24 ppt|
Pollution is possible, take care = Salinity between 21 and 24 ppt
Pollution is likely, avoid swimming today = Salinity is less than 21 ppt
The above thresholds have been calculated based on Hornsby Shire Council's water quality monitoring program and the 2018 National Health and Medical Research Council Guidelines for Managing Risks in Recreational Water. These thresholds take into consideration the NHMRC categories based on the 95th percentile for Enterococci and the salinity values being monitored from Council's on-site water quality monitoring station. These thresholds will change as more bacteria data comes available in particular after wet weather sampling. The occurrence of freshwater in the estuary following rainfall increases the likelihood of pollution being present. Obvious signs of stormwater pollution are water discoloration as well as debris in the water and tide line. When pollution is likely, swimmers may be at increased risk of contracting illness and swimming at these times should be avoided.
This system utilises recorded data captured by Manly Hydraulics Laboratory (MHL) on behalf of Hornsby Shire Council. Recorded data is download at 7 am each morning at all monitoring locations. Displayed salinity values are calculated as the average of salinity measurements for the latest 24 hours of data. At locations without recorded data, salinity is estimated using correlated values from nearby recorded data.
IMPORTANT: This information has been recovered directly from automatic recording equipment and has not been quality controlled by MHL. The State of NSW (of which MHL is an agency) does not warrant the quality, accuracy, currency, reliability or correctness of this information and accepts no liability for any loss, injury (including death), or damage which any person relying on this information may suffer.