Managing uncertainty when informing about swimming conditions downstream of urbanisation

Dr Ana Rubio1, Ms Kristy Guise1, Mr Roman Kadluczka2, Dr Bronson McPherson2

1Hornsby Shire Council, Hornsby, Australia, 2Department of Planning, Industry and Environment – MHL, Manly Vale, Australia


Coastal communities inherently aspire to be able to swim in estuaries.  For coastal managers to deliver on this aspirational goal there is a need to manage the impacts of increasing urbanisation on the health of urban creeks.  Urban creeks play an important role connecting upstream urban areas with downstream estuarine sites and thus provide the means for pollutant transport to popular estuarine swimming areas.  The main challenge is to be able to swim in locations which are potentially impacted by stormwater run-off due to increased impervious surfaces and potentially polluted from wet weather discharge from local wastewater treatment plants (WWTPs) when treatment capacity is exceeded.

The Hawkesbury Estuary, located 25km north of Sydney, is used as an example to highlight the challenges of managing swimming in estuaries. Specifically, the headwaters of Berowra Creek, currently supports a population of 71,736, has two WWTPs and one estuarine recreational site used for camping, fishing, kayaking and swimming. Hornsby Council undertakes intensive water quality monitoring in this area which includes the deployment of real-time water quality monitoring stations and the collection of a range of other variables, in particular bacteria levels that are used to assess compliance against the NHMRC (2008) swimming recreational water guidelines. The presentation will focus on the challenges to manage uncertainty in a number of aspects: making decisions based on water quality information collected, managing the risk of potential pollution and communicating swimming conditions to recreational users.


Ana is an environmental scientist with over 15 years of strategic, operational and management experience on estuary processes and threats. Ana’s current role is to manage the Lower Hawkesbury and is currently leading the development of the Hawkesbury Coastal Management Program. Ana  is also involved in maintaining and responding to an extensive estuary monitoring program in the Hawkesbury that involves real-time telemetry-based water quality monitoring stations. Data from the program has been analysed for a wide range of applications including predictive modelling of public health at estuarine swimming sites, ecosystem estuarine health scores and long-term trend analysis of water quality.