Waterway Health Review
Hornsby Shire Council has monitored water quality to assess aquatic ecosystem health since 1994. This program is one of the most intensive monitoring programs undertaken by any Local Government in NSW.
In 2019, Council finalised a Waterway Health Review using the long-term data to provide a comprehensive understanding of the spatial and temporal variability and current condition of our creeks, estuary and river systems. Findings from the review were used to make recommendations of management actions to protect our valuable waterways into the future.
The Waterway Health Review provides a longer-term assessment of the health of our local creeks and estuaries and how things have changed over time and place across the Shire. The Review analysed and interpreted a long-term data set and used this information to make future management recommendations.
The Review analysed 22 years of water quality data collected from 35 long-term sites to identify changes in water quality and assess environmental condition by comparing observed water quality data to Regional Environmental Health Values (REHVs). REHVs are adopted guideline values that were developed for HSC based on a combination of the conditions observed at two long-term reference sites (i.e. located in undisturbed bushland catchments) and ANZECC (2000) aquatic ecosystem health guideline values. Specific objectives of this analysis were to:
- Identify significant temporal trends in water quality monitored at freshwater and estuarine sites
- Determine how water quality conforms against REHVs at freshwater and estuarine sites
- Identify site-specific risks to water quality and recommend management options to achieve water quality objectives
- Use knowledge gained from long-term water quality monitoring in association with established decision-making frameworks to guide HSC’s monitoring program into the future.
Significant findings of the Waterway Health Review include:
- In general, water quality at most long-term freshwater sampling sites has remained relatively stable despite an ever-growing population and increasing development pressure
- Waterways in urban areas generally have poorer water quality through time
- Long-term improvements in water clarity have been achieved at many freshwater sites, however, persistently elevated nutrient concentrations, electrical conductivity and pH remain an issue
- Long-term improvements in phosphorus concentrations have been achieved at two out of three monitoring sites (Larool Creek, Thornleigh & Sams Creek, Mt Kuring-gai) both associated with industrial land use
- Estuarine sites in the Hawkesbury River are influenced by impacts from the wider Hawkesbury-Nepean system, particularly in relation to nutrient enrichment
- Most sources of faecal bacteria in both fresh and estuarine waterways are associated with pulse, or intermittent, pollution events that are likely to be rainfall related
- Significant improvements in nutrient concentrations are evident following the completion of Sydney Water upgrades to the Hornsby Heights and West Hornsby Wastewater Treatment Plants in 2003, however, no further improvements are evident since this time.
The findings and recommendations from the Review have formed the foundation for the refinement of Council’s monitoring program to ensure that it remains reliable, relevant, and integrated with other Council programs.