Hawkesbury Monitoring

HawkesburyWatch is a near real-time rainfall, water level and water quality monitoring system which provides information to Hornsby Council and the public of NSW. This management system has been developed by MHL for Hornsby Council to provide maps of Salinity, Temperature and Swimming Conditions in the lower Hawkesbury river.
Swimming conditions in this website are predicted from the likelihood of bacterial contamination at the swimming sites. 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 the algae hotline 1800 999 457.

Swimming Conditions

Pollution is likely Swim at own risk Pollution unlikely

Swimming SiteSalinity
Parts per 1000
Latest dataStatus% 'Pollution unlikely'
in the last 12 months
Bar Island32.2 ppt25 Feb 00:0079
Calabash Bay30.4 ppt25 Feb 00:0059
Crosslands Reserve21.9 ppt25 Feb 00:000
Gunyah Point34.9 ppt25 Feb 00:0096
Laughtondale17.0 ppt25 Feb 00:0085
last updated :2018-02-26 06:20

          Pollution is likely (Salinity is less than 21 ppt)
          Swim at own risk (Salinity is between 21 and 24 ppt)
          Pollution is unlikely (Salinity is greater than 24 ppt)

*Thresholds above do not apply to the upstream locations at Courangra and Laughtondale. At these locations thresholds are based on the historical 30th and 10th salinity percentiles.

Salinity data has been used to predict the likelihood of bacterial contamination at swimming sites in the Hawkesbury. 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 MHL on behalf of HSC and a 3D hydrodynamic model configured by Office of Environment and Heritage for HSC of the Hawkesbury-Nepean estuary. Model input data is sourced from various agencies including Bureau of Meteorology, MHL, SCA, OEH and Dept of Primary Industries Office of Water.
Data is downloaded at 2am each morning and the model is run based on the previous days monitored data. The results will show interpolated contour maps based on the previous day.

IMPORTANT: This information has been recovered directly from automatic recording equipment and has not been quality controlled by Manly Hydraulics Laboratory (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.