The water samples are assessed against the Australian and New Zealand Guidelines for Fresh and Marine Water Quality. These guidelines support water quality management across Australia and New Zealand.
Electrical conductivity
Electrical conductivity measures the total salts in water. It can indicate changes in the chemical condition of an aquatic ecosystem.
Guideline value: ≤ 500 µS/cm
pH
pH measures how acidic or alkaline water is. The scale ranges from 0 to 14, where 7 is neutral. Changes in pH can directly affect aquatic life and can also influence the toxicity of other pollutants.
Guideline value: 6.5 – 8.5
Dissolved oxygen
Dissolved oxygen refers to the amount of oxygen in water. It is an important indicator of a waterway’s ability to support aquatic life. Dissolved oxygen can decrease due to natural events, such as heavy rainfall, or pollution events, such as sewage overflows.
Guideline value: ≥ 6 mg/L
Turbidity
Turbidity describes how clear or cloudy water is. Higher turbidity means there are more suspended particles in the water, making it appear murkier. Turbid water can reduce the amount of light entering the water and may limit aquatic plant growth.
Guideline value: < 5 FAU
Nitrate, total phosphorus and total nitrogen
Nitrogen and phosphorus are essential for aquatic life. However, excessive concentrations can promote nuisance plant growth and cause eutrophication, also known as nutrient pollution. Elevated nitrogen and phosphorus can result from natural sources and human activities, including cleared land, fertiliser run-off and sewage discharges. Total nitrogen and total phosphorus measure all forms of nitrogen or phosphorus in a sample. Nitrate is an inorganic form of nitrogen that is available for plant growth.
Nitrate guideline value: ≤ 0.3 mg/L
Total phosphorus guideline value: ≤ 0.05 mg/L
Total nitrogen guideline value: ≤ 1.0 mg/L
Enterococci
Enterococci are bacteria found in the intestinal tracts of humans and animals and are commonly associated with sewage contamination. Some areas of The Hills Shire are not connected to Sydney Water’s wastewater system and rely on onsite sewage management systems, which often use land disposal. If these systems are not maintained, they can pose a risk to waterways.
While no criteria have been adopted for enterococci, samples are being collected and analysed by Sydney Water. The results will be used to identify areas where further investigation may be needed, including targeted inspections of onsite sewage management systems.