The where, what, how and why of monitoring
Council undertakes comprehensive estuarine and freshwater monitoring to understand, report on and respond to the health of the waterways in Hornsby Shire. Routine water quality monitoring commenced in 1994 with the sole objective of determining whether water quality in the Shire was improving or declining through time. Over time, the monitoring program has expanded to incorporate multiple different monitoring approaches responding to a wide range of questions:
- Is water quality changing through time?
- What is the current health of the waterways in Hornsby Shire?
- What is the impact of different land uses on waterways? (e.g. impacts from industrial, rural or urban catchments)
- What is the impact of different point source pollution on waterways? (e.g. wastewater treatment plant discharge or construction site runoff)
- How are the catchment remediation (stormwater quality improvement) devices performing?
- How are the stormwater harvesting systems performing?
- How are climate drivers influencing the baseline conditions of our waterways?
- What is the impact of rainfall on waterway health?
- Do certain water quality conditions pose a risk to public health?
All of Council’s monitoring is carefully undertaken with stringent quality-assurance and quality-control measures and protocols. Waterway health monitoring activities are undertaken by environmental scientists and ecologists, both internal to Council and from external consultancies. The monitoring programs incorporate a comprehensive suite of physical, chemical, and biological indicators (multiple lines of evidence) to determine the health of waterways.
Data from all of Council’s monitoring activities is used to influence and inform catchment management decisions to protect or enhance local waterways. There are several management responses that can be employed by Council in response to monitoring findings, and they generally fall into one of the following categories:
- Planning and compliance
- Research and investigation
- Education and collaboration
- Further monitoring
Reference conditions
One approach to measuring the impact of human activities on waterway health is to compare monitoring data against a ‘reference’ condition. Data from reference sites demonstrate the natural variation of water quality in creeks that have minimal human impact, providing a benchmark against which other sites can be compared. Reference sites have mostly undisturbed, bushland catchments so are not impacted by human changes in the catchment. These sites demonstrate the background temporal variation that might be expected at all sites. Monitoring reference sites is an important way to keep an eye on how waterway conditions respond to drivers outside of the immediate catchment, such as climate variability.
Hornsby is lucky to have a significant amount of land protected by National Parks, and Council routinely monitors 4 reference sites. The 2 principal long-term reference sites are located in the lower reaches of Marramarra and Ku-ring-gai Chase National Parks. An additional two sites were established in Muogamarra Nature Reserve and Lane Cove National Park to improve the understanding of reference conditions higher in the catchments.
These sites are monitored monthly and are characterised by low pH, low nutrient input, good clarity, and low bacteria levels. Rainfall runoff takes longer to reach these waterways, slowly permeating through the heavily vegetated catchments which also reduces the amount of sediment entering the creeks during heavy rainfall.
Long Term Reference Sites
Sampling parameters
In-situ measurements using a portable multimeter
- Temperature
- Electrical conductivity
- Turbidity
- Dissolved oxygen
- pH
- Salinity
Grab samples for laboratory analysis
- Total suspended solids
- Bacteria
- Nutrients
- Chlorophyll-a
- Alkalinity
- CBOD5 (5-day carbonaceous biological oxygen demand)
Useful links
Industrial sites
Industrial land-use continues to place significant pressure on waterway health in Hornsby Shire. Unfortunately, the critical goods and services provided by these commercial and industrial locations have led to significant modification of the catchments. In addition, the widespread use of products such as concrete and harsh detergents/surfactants often result in stormwater contamination. Council routinely monitors three sites adjacent to the Thornleigh, Hornsby and Mt Kuring-Gai industrial areas to better understand the impacts from industrial land use. A collaborative approach to managing industrial areas is important, with many businesses operating under state government EPA licences.
Industrial sites are monitored monthly and are characterised by highly elevated pH and nutrient levels, and lower dissolved oxygen. These sites also receive pulses of bacterial contamination, most likely due to problems with ageing wastewater (sewerage) infrastructure during wet weather. Rainfall runoff quickly reaches the creeks in these catchments, being directed straight off the hard surfaces to stormwater drains, carrying pollutants straight to the local creeks and waterways. Industrial areas also generally contain high percentages of hard (impervious) surfaces, which means that runoff and the flows in downstream creeks can increase very quickly. As a consequence, nearby waterways can become highly eroded, often resembling large concrete gutters instead of natural creeks.
Industrial Sites
Sampling parameters
In-situ measurements using a portable multimeter
- Temperature (oC)
- Electrical conductivity (µS/cm, mS/cm)
- Turbidity (NTU)
- Dissolved oxygen (%sat, mg/l)
- pH
- Salinity (PPT)
Grab samples for laboratory analysis
- Total suspended solids (TSS)
- Bacteria (Faecal coliforms, E.coli, enterococci)
- Nutrients (TN, TP, NH3-N, NOx-N, SRP)
- Fluoride (provides an indication of how much portable water runoff is reaching waterways in these heavily modified catchments)
- CBOD5 (5-day carbonaceous biological oxygen demand)
Useful links
Stormwater harvesting, treatment and resuse
In recent years, the need to conserve water and to reduce the impacts of urban stormwater on creeks has led to an increase in the harvesting of stormwater for reuse. Stormwater harvesting involves collecting stormwater runoff from parks, paved areas and drains in a selected catchment. The collected water is then treated onsite to a standard that is fit for purpose (e.g. irrigation) and reused locally.
A number of stormwater harvesting and reuse systems have been constructed in Hornsby Shire through the Catchment Remediation Rate Program, with the majority of them providing irrigation for sports ovals. To ensure that the correct treatment is in place, Council monitors the quality of the runoff collected in each catchment. Once the facilities are constructed, treated stormwater is tested to make sure it is safe and suitable for reuse.
Stormwater harvesting, treatment and reuse sites are audited annually, prior to the main irrigation season.
Sampling parameters
In-situ measurements using a portable multimeter
- Temperature (oC)
- Electrical conductivity (µS/cm, mS/cm)
- Turbidity (NTU)
- Dissolved oxygen (%sat, mg/l)
- pH
- Salinity (PPT)
Grab samples for laboratory analysis
- Total suspended solids (TSS)
- Bacteria (Faecal coliforms, E.coli, enterococci)
- Fluoride
- UV % transparency (influences the effectiveness of the UV treatment process in removing bacteria)
Find out further information on Council’s water conservation initiatives