Darwin Harbour water quality report 2021

Every year the Darwin Harbour water quality report assesses the water quality of Darwin Harbour against the Darwin Harbour water quality objectives.

Water quality data were collected by the Aquatic Group of the Department of Environment, Parks and Water Security and supplemented by monitoring data from Power and Water Corporation and INPEX in 2021.

Nine reporting zones represent different physical environments in the harbour, which feature marine biota such as seagrass beds, coral reefs and fringing mangroves.

The Harbour's water quality was largely graded very good in 2021 with an overall grade of ‘A’.  An exception was Buffalo Creek estuary, which was impacted mainly by wastewater discharge from the Leanyer-Sanderson sewage treatment plant.

No marine pests were detected in 2021 and the beaches were suitable for swimming throughout the dry season.

2021 water quality report

2021 Water quality report at a glance PDF (2.7 MB)

Find out more about each zone.

• Zone 1: Elizabeth River Estuary
• Zone 2: East Arm
• Zone 3: Middle Arm
• Zone 4: West Arm
• Zone 5: Middle Harbour
• Zone 6: Outer Harbour
• Zone 7: Shoal Bay
• Zone 8: Buffalo Creek
• Zone 9: Myrmidon Creek

Overall water quality index

Station data

Report data collection

Water quality data for the Darwin Harbour report cards were collected during the dry season. Data collection was restricted to neap tides to minimise variability due to tidal influence.

Surface water quality (pH, dissolved oxygen, salinity, temperature and turbidity) was measured at one-second intervals along continuous transects across the nine reporting zones, using a flow-cell method (CFM - Continuous Flow Method) that continuously pumps water through a water quality instrument. More than 100,000 measurements were made in 2021 using this method.

Water samples were also collected from over 100 sites and analysed for nutrients and chlorophyll-a.