2024 water quality report

Annually the Darwin Harbour water quality report assesses the water quality of Darwin Harbour marine and estuarine waters against the Darwin Harbour water quality objectives or guidelines. These objectives have been developed to protect the values of the estuary according to declared beneficial uses.

Water quality data is collected by the Aquatic Group of the Department of Lands, Planning and Environment and was supplemented by monitoring data from Power and Water Corporation in 2024.

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

The Harbour's water quality was largely graded as good to very good in 2024 with an overall grade of 'B'. An exception was Buffalo Creek estuary, which is impacted mainly by wastewater discharge from the Leanyer-Sanderson sewage treatment plant.

The department continues to monitor the health of Darwin Harbour. Water quality is also supported by programs of the Integrated Marine and Monitoring Research Program (IMMRP) providing critical information on the condition of sediments and mangroves in conjunction with monitoring pressures in the region.

2024 water quality report

Darwin harbour water quality at a glance 2024 PDF (4.7 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 2024 using this method.

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