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Key environmental pressures

There were limited cyclone impacts experienced in the inshore Reef region in 2021-22.  

In early January, ex-Tropical cyclone Tiffany crossed Cape York and caused moderate floods in the Annan-Endeavour, Stewart and Normanby Rivers.

In early February, significant rainfall in south-eastern Cape York caused major flooding in the Normanby Basin and Princess Charlotte Bay.

The 2021-22 monitoring year was characterised by some relatively late heavy rainfall events in April and May 2022, marking an unseasonally wet dry season that was experienced in many of the regions.

The late rains caused significant flooding in Cape York (Annan River) and the Wet Tropics (Tully and Russell-Mulgrave Rivers), and also the very southern NRM regions (Fitzroy and Burnett-Mary).

Overall, rainfall and river discharge was just above the long-term median for the Reef. The northern NRM regions (Cape York, Wet Tropics and Burdekin) had discharges around the long-term median, while the Mackay–Whitsunday region was around half of the long-term median, and the Fitzroy region was 1.5 times above the long-term median.

The Burnett–Mary region had very high discharge in the 2021-22 water year at nearly nine times above the long-term median.

Sea-surface temperatures were slightly above long-term averages for the 2021–22 summer, especially in the central region (Burdekin and Mackay-Whitsunday), where signs of bleaching and partial bleaching were detected at most sites in the Burdekin. 

Read the Marine Monitoring Program Annual Report Inshore Water Quality Monitoring 2021-22.

How did environmental pressures affect inshore water quality?

  • Inshore water quality findings:
  • Annual water quality condition was ‘moderate’ in the Wet Tropics, Burdekin, and Mackay-Whitsunday regions and ‘good’ in Cape York (and ‘very good’ for the Annan-Endeavour Basin) and Fitzroy.
  • Long-term water quality trends showed improvement in regions where this indicator is available for reporting (Wet Tropics, Burdekin, Mackay-Whitsunday, and Fitzroy).
  • Water quality indicators such as Chlorophyll a, Total Suspended Solids, and phosphate broadly met marine guideline values in most regions, with recent trends of improving conditions.
  • In the 2021-22 monitoring year, particulate phosphorus and Secchi depth were generally improving or stable across all regions.
  • Nitrate/nitrite, particulate nitrogen, and Secchi depth did not meet the marine guidelines in most regions but are showing a broad trend of improvement or stability over the past five years. This reverses the degrading trends of conditions seen earlier in the monitoring program (these parameters have been monitored for 17 years).
  • There was a high frequency of exposure in the inshore region to Reef Water Type 1 (brown waters), which contains high levels of sediment and dissolved organic matter.
  • Mid-shelf to offshore areas were occasionally exposed to Reef Water Type 3 (greenish-blue waters), which provide high light penetration and are often a result of offshore upwelling. 
  • The area exposed to potentially high risk in relation to poor water quality in the 2021–22 monitoring year was spatially limited to the inshore region. The area exposed to the highest risk categories equated to nearly 10,000 km2. 

What is monitored and where?

  • Inshore water quality is monitored for:
  • Total Suspended Solids, turbidity, and Secchi depth (indicators of water clarity)
  • Chlorophyll a (a measure of phytoplankton abundance, which responds quickly to nutrients)
  • Nutrients (dissolved and particle forms of nitrogen, phosphorus, and carbon) 
  • Sea-surface temperature and salinity.


  • Water quality is monitored in four regions:
  • Cape York
  • Wet Tropics
  • Burdekin 
  • Mackay-Whitsunday.

Recently, the reporting of the Fitzroy region has been facilitated via a partnership between the Australian Government’s Reef Trust, the Great Barrier Reef Foundation, and the Australian Institute of Marine Science. 

Learn more on the Marine Monitoring Program Annual Report Quality Assurance and Quality Control Manual 2020-21

Updated 24 Mar 2023
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