Council, in collaboration with the NSW Department of Climate Change, Energy, the Environment and Water (DCCEEW), monitors water quality and ecosystem health in estuaries across the Shoalhaven local government area (LGA).
The results of this monitoring program are used to generate estuary health report cards, which enables Council to compare water quality and ecosystem health over time.
Council monitors water quality in estuaries across the Shoalhaven LGA by measuring ecosystem health indicators including:
- abundance of algae
- water clarity
- a range of supporting indicators, such as salinity, oxygen, pH, temperature and suspended sediments
Whats the difference between ecosystem health and recreational health?
'Ecosystem health' is the ability of a waterway to support a diverse range of healthy plants and animals. This means clear water with low algae levels, good levels of dissolved oxygen, and low levels of nutrients, pollutants and contaminants. Healthy ecosystems have high biodiversity and a range of available habitats.
'Recreational health' refers to the suitability of a place for activities involving direct contact with a waterway, like swimming. Council takes samples from different estuary locations to assess recreational health, basing its judgement on potential risks to public health.
These indicators inform Council about the health of ecosystem processes and how the water quality might support and enhance biodiversity and habitats for each estuary.
Council’s Environmental Health Unit develop estuary health report cards based on the two main water quality indicators: algal abundance and water clarity in accordance with DCCEEW’s Protocol.
This assessment does not measure environmental issues such as drinking water quality, safety for swimming, heavy metal contamination, disease, bacteria, viruses, or ability to harvest shellfish or fish.
A healthy estuary has clear water and low levels of algal growth. Each estuary health report card gives an overall grade for the health of an estuary for a specific year based on combined measurements of water clarity and algal abundance.
The grades range from A (excellent health) to E (very poor health):
- A – excellent
- B – good
- C – fair
- D – poor
- E – very poor.
Algae levels
Algae are a diverse group of mostly aquatic plants that include microscopic algae found in waterways.
We measure chlorophyll — a pigment that gives plants their green colour — to get an indication of how much algae is present in a water sample.
Algae can grow quickly when high levels of nutrients such as nitrogen and phosphorous are present in a waterway. Nutrients can enter an estuary through urban stormwater runoff, agricultural runoff and sewage and sediment runoff from the land.
The amount of light, water clarity and water temperature also influences the growth of algae in a waterway.
Excessive growth can cause an ‘algal bloom’ which can reduce the amount of light available to aquatic plants and animals. The algae eventually die and are eaten by bacteria, which remove oxygen from the waterway. The anaerobic (low or no oxygen) conditions potentially make the waterway uninhabitable for other species, which can result in issues like fish kills.
Low levels of algae usually indicates that low levels of nutrients are entering and staying in a waterway. This results in a ‘good’ grade for algae.
Water clarity
Water clarity is determined by turbidity - i.e. a measure of how much material, such as sediments or organic matter, is stirred up or suspended in the water.
High levels of turbidity indicate that excessive amounts of sediments are present in an estuary, which equates with poor water quality.
Fine sediment can stay suspended in water until it settles in low energy, shallow areas of an estuary, like seagrass meadows. Coarser material tends to sink and settle in deeper sections of an estuary.
High turbidity can have negative impacts on aquatic ecosystems. For example, it can reduce the amount of light filtering through the water, which limits the ability of important underwater plants like seagrass to grow.
Alternatively, low levels of turbidity and good water clarity indicate there is a suitable amount of sediment, organic matter and nutrients entering and remaining in an estuary, which equates with good water quality.