Key environmental pressures

Environmental conditions over 2022–23 monitoring season were reasonably benign across the inshore Reef. 

Over the 2022–23 wet season, rainfall and river discharge were just above the long-term median for the total Reef-wide discharge. Three regions had discharge well above the long-term median including the Cape York, Burdekin, and Mackay–Whitsunday. River discharge in the Wet Tropics and Fitzroy regions was close to the long-term median, while the Burnett–Mary region was slightly below the long-term median. 

Major floods occurred in the Cape York and Mackay–Whitsunday regions. In Cape York, major floods occurred in the Pascoe and Normanby Rivers. Floods of the Normanby started from 28 December 2022 and continued throughout January 2023. After a short decline, discharge from the Normanby River increased again in mid-February, remaining at flood levels until mid-March. 

In the Mackay–Whitsunday, high discharge occurred in the Proserpine and O’Connell Basins in January 2023. Despite considerable rainfall in the Mackay area and surrounds, the rainfall event did not result in large flows in the Pioneer River.

Sea surface temperatures were above average in inshore waters during the 2022–23 monitoring season, with pre-summer temperatures above 2 degrees above long-term average in waters north of the Whitsundays. Late summer and autumn temperatures reached more than 3 degrees above normal in some areas between Townsville and Cape Tribulation. 

• Read the latest Marine Monitoring Program Annual Inshore Water Quality Report 2022–23
• Read the latest Marine Monitoring Program Annual Inshore Pesticide Report 2022–23

How did environmental pressures affect inshore water quality?

Inshore water quality findings:

• Long-term trends showed that overall water quality has improved across the inshore Reef after years of deterioration, particularly between 2008 and 2018.
• In 2022–23, the Long-term Water Quality (WQ) Index showed trends of improvement in water quality in all regions where this score can be generated.

Figure 1: Temporal trends in the regional Long-term Water Quality (WQ) Index scores for the Wet Tropics, Burdekin, Mackay-Whitsunday and Fitzroy regions. Values are indexed scores scaled from -1.0 to 1.0 and graded: ■ = very good (1 to 0.5), ■ = good (0.5 to 0), ■ = moderate (< 0 to -1/3), ■ = poor (< -1/3 to -2/3), ■ = very poor (< -2/3 to -1). Note scores are unitless. 

• The annual Condition WQ Index scored water quality as either 'good' or 'moderate' in all regions.

Figure 2: Temporal trends in the regional Annual Water Quality (WQ) Index scores for the Cape York, Wet Tropics, Burdekin, Mackay–Whitsunday and Fitzroy regions. Values are indexed scores scaled from -1.0 to 1.0 and graded: ■ = very good (1 to 0.5), ■ = good (0.5 to 0), ■ = moderate (< 0 to -1/3), ■ = poor (< -1/3 to -2/3), ■ = very poor (< -2/3 to -1). Note scores are unitless. 

• Key water quality indicators such as Chlorophyll a (Chl a), phosphorus, and total suspended solids met guideline values (GVs) in all or most regions. Trend analysis has shown that since 2015, all water quality indicators have improved or been stable in all focus regions with one exception (particulate nitrogen in the Tully focus region, which has shown a trend of deterioration). Nitrate/nitrite has shown a trend of improvement in most focus regions, although concentrations are currently well above GVs (except for parts of Cape York).
• This is a promising finding for nitrate/nitrite and if current trends continue, concentrations may approach GVs in the next few years.
• The area exposed to a potential risk in 2022–23 was spatially limited relative to the scale of the Reef with 91% exposed to no or very low potential risk.
• Only the inshore Reef waters, including the enclosed and open coastal were exposed to the highest categories of potential risk (III and IV), including 29% of surveyed seagrass area.

Inshore pesticides findings:

• Pesticides were detected in all sites monitored. Diuron, atrazine, hexazinone and tebuthiuron were the most prevalent pesticides quantified across all sites. 
• Total pesticides concentrations were highest at sites in the Mackay–Whitsunday region (Flat Top Island, Sarina Inlet, and Repulse Bay), which corresponded to high rainfall in those areas in January 2023.

What is monitored?

Water quality monitoring is routinely undertaken during wet and dry seasons (left), along permanent transects located from river mouths to open coastal areas. Additionally, monitoring of flood plumes is conducted as required during flood events (right).

Where is water quality monitored?

• Water quality is monitored in five regions:
• Cape York
• Wet Tropics
• Burdekin
• Mackay-Whitsunday
• Fitzroy*

*Monitoring of water quality in the Fitzroy region is done through the Fitzroy Basin Marine Monitoring Program, which is done in 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
• In-situ Water Quality monitoring data can be downloaded from AIMS.