Freshwater and Catchment Health

Council monitors the health of freshwater waterways through a comprehensive waterway health monitoring program. Multiple lines of evidence are combined to develop an understanding of the condition of our creeks and inform the appropriate management responses. Monitoring at these sites incorporates:

  • Water quality monitoring
  • Macroinvertebrate monitoring
  • Freshwater algal diatom monitoring (commencing 2023)
  • Riparian vegetation condition assessment
  • Geomorphological condition assessment.

Council currently monitors 21 sites selected to represent the spatial distributions of major catchments and creeks throughout the Shire. Where possible, sites have been selected to provide a longitudinal overview of waterways. For example, seven sites are monitored along Berowra Creek; four sites in the freshwater stretches starting at the headwaters and meandering downstream to the estuarine confluence, with another three sites in the Berowra Creek estuary.

By combining the findings from these comprehensive waterway health indicators, Council has a better understanding of short-term, intermediate-term and long-term responses to catchment pressures quantify waterway health and prioritise management responses.

For results of Council’s freshwater waterway health monitoring see Waterway Health Portal developed by CASI group from UNE.

Water quality is monitored each season (quarterly) and the parameters include:

In-situ measurements using a portable multimeter:

ParameterMeasureWhat does it tell us?
Temperature oC Water temperature influences the rates of chemical and biological processes and affects other measured parameters (e.g. as temperature increases, the maximum amount of dissolved oxygen decreases).
Electrical conductivity µS/cm or mS/cm Used in freshwater as a measure of the saltiness of the water and is measured on a scale from 0 to 50,000 uS/cm. Electrical conductivity is measured in microsiemens per centimeter (uS/cm). Freshwater is usually between 0 and 1,500 uS/cm.
Turbidity NTU Indicates how much particulate matter is in a water sample. If turbidity appears in the water, it may indicate water pollution.
Dissolved oxygen %sat, mg/l A measure of oxygen available in water. It is an essential parameter in assessing water quality because of its influence on the organisms living within a body of water. Oxygen is used during the decomposition of organic matter and low levels of oxygen can indicate a waterway is out of balance, e.g. the production of too much algae that then breaks down and removes oxygen from the water.
pH Units Measured between 0 and 14 to determine how acidic or alkaline, with 7 being neutral.
Salinity PPT Use in estuarine and marine water as a measure of the dissolved salt content.

Grab samples for laboratory analysis:

ParameterMeasureWhat does it tell us?
Total suspended solids TSS TSS are a measure the amount of particulate matter (tiny pieces of things) floating in water. TSS can be useful as an indicator of the effects of runoff from construction, agricultural practices, sewage treatment plant discharges, and other sources. As with turbidity, concentrations often increase sharply during rainfall
Chlorophyll-a µg/L Chlorophyll-a provides a good assessment of the primary production or algal activities in a waterbody. The direct causes of algal blooms are often associated with increased total phosphorous (TP) and/or total nitrogen (TN) levels in a waterbody
Bacteria Faecal coliforms, E.coli, enterococci Bacteria measures a water source's safety by estimating the number of bacteria in a sample and determining which species are present. The initial process doesn't detect dangerous organisms. Rather, it detects “indicator organisms” that are more common in places with higher amounts of pathogens
Nutrients TN, TP, NH3-N, NOx-N, SRP Nutrients are essential for the survival of aquatic organisms and nutrients are tested to ensure levels remain safe. The overuse of fertilizers, which contain nitrogen, phosphorus, and potassium, have the potential to be harmful if ingested by humans and animals.

Nitrogen in water can come from both organic and inorganic sources. Nitrogen from organic sources includes animal wastes and living things, whereas nitrates are the most common form of inorganic nitrogen. Nitrates are odourless and colourless, so it is crucial to test drinking water to determine levels of nitrates. High concentrations can cause congenital disabilities and become toxic to livestock.

Phosphorus limits plant growth in a waterbody, so only adding a small amount of this can cause excessive plant growth, which can use up oxygen, affecting fish and macroinvertebrates. Runoff, building activities, damage to vegetation, fertilizers, and poorly functioning septic tanks can all affect phosphorus levels.

(total & bicarbonate)
pH Measuring alkalinity is important in determining a stream's ability to neutralize acidic pollution from rainfall or wastewater. It's one of the best measures of the sensitivity of the stream to acid inputs.

Additional site information collected:

  • Weather observations
  • Presence of oily films, odours, frothing
  • Presence of nuisance organisms
  • Flow ranking
  • Water appearance
  • Photographs

Macroinvertebrates (water bugs) are a widely accepted biological measure of waterway health as each type of macroinvertebrate requires certain environmental conditions to survive, grow and reproduce. Some are tolerant of water pollution, whereas others are very sensitive. This means you can tell a lot about the environmental conditions in a water body from the types of macroinvertebrates present and in what numbers (abundance).

Macroinvertebrate communities are sampled annually during Spring (weather permitting). Samples are collected consistent with the NSW AUSRIVAS (Australian River Assessment System) Sampling and Processing Manual.

The following indices are calculated to provide an understanding of the macroinvertebrate communities present at each site:

  • Abundance – the total number of macroinvertebrates present in a sample
  • Taxonomic richness – the number of different types of macroinvertebrates (taxa) present in that community. Richness measures the overall diversity of the community sampled. Generally, taxa richness will decrease with decreasing water quality
  • EPT richness – the total number of taxa within the “pollution sensitive” orders Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies)
  • SIGNAL2 – a SIGNAL2 score gives an indication of water quality and when considered together with richness, can provide an indication of the types of pollutants and the physical and chemical conditions affecting the community.

Freshwater benthic algal diatoms are recognised as a useful biological indicator for waterway health. Diatoms are the primary food source at the base of the food chain for everything living in fresh water, which includes zooplankton, crustaceans, and amphibians. When nutrients are consumed by these organisms, they are unavailable to weeds and algae. Diatoms also increase dissolved oxygen in the water.

Diatoms respond to water quality chemistry, such as nutrient enrichment, and may be less influenced by physical conditions such as altered habitat or flow regimes commonly seen in urban areas. As such, they are considered an important biological response indicator, particularly in urban areas.

Council holds diatom data for the period 2002-2007 collected as part of a five (5) year aquatic ecosystem health monitoring program and will be reintroducing freshwater algal diatoms to our routine waterway health monitoring from 2023. Diatoms will be monitored annually, during Spring, in addition to macroinvertebrate monitoring.

Riparian vegetation, in the most general sense, refers to the plants surrounding a waterway at the interface between the waterway and the land. More specifically, the riparian zone is defined as any land which adjoins, directly influences, or is influenced by a body of water. An intact riparian zone can buffer a waterway from influences in the wider catchment and support vital ecological services. When combined with a vegetated catchment the riparian zone provides important protection for our creeks.

Council commenced routine riparian condition assessment in 2017. Riparian vegetation is assessed annually in spring and early summer. The following categories are monitored using transects, quadrats and rapid data points (RDPs), to give an indication of the riparian vegetation ecosystem function:

  • Key habitat features
  • Leaf litter depth
  • Fauna observations
  • Native vegetation cover
  • Exotic vegetation cover
  • Canopy cover
  • Connectivity

Geomorphological condition tells us how sediment moves around a waterway, is influenced by catchment erosion and how sediment transport processes physically influence ecological habitats and processes within a waterway. Assessments of geomorphic condition reflects the size, shape, and geology of the waterway along with the position in the catchment. Consideration is given to the condition of stream banks and stream beds along with any local management that directly impacts the waterway reach.

Council commenced routine geomorphological condition assessment in 2017. The following conditions are assessed to give an indication of site-level geomorphological condition:

  • Bank condition – undercutting, slumping, active erosion or deposition, exposed tree roots
  • Bed condition – active erosion or deposition/smothering
  • Management – human access, vegetation clearing, livestock access, fencing, riparian or instream works