Water
quality
Key findings in the Ross and Black Basins from the 2026 Report Card
The Ross Basin, home to most of Townsville’s population, maintained ‘good’ water quality in the freshwater (upstream) area, but declined to ‘moderate’ in the estuarine (downstream) zone.
In the freshwater zone, new data provides a first glimpse into the Stuart Creek sub-basin, helping to fill an important gap. Early results indicate a system under pressure, with an overall ‘very poor’ grade driven by excess nutrients (‘very poor’) and low dissolved oxygen. This pattern is consistent with other challenged waterways in the Basin. The Bohle River, for example, recorded ‘poor’ water quality for the seventh consecutive year, also influenced by high nutrients and low oxygen levels.
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We’re working to secure additional data in the Stuart Creek sub-basin to build a more complete picture.
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Across the broader Ross freshwater area, nutrient levels declined slightly in the Lower Ross River sub-basin. This was driven by conditions at Gleesons Weir, where dissolved inorganic nitrogen (DIN) grades dropped from ‘very good’ to ‘moderate.’ In contrast, the other weirs maintained similar nutrient grades to the previous year. Low dissolved oxygen remains an ongoing concern across these sites. Aplin’s Weir recorded a ‘very poor’ grade, marking the sixth consecutive year of declining oxygen levels. Gleesons Weir remained ‘poor,’ while Blacks Weir showed some improvement, increasing from ‘poor’ to ‘moderate.’
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Further upstream, the Upper Ross River sub-basin continued to perform strongly, maintaining a ‘very good’ water quality grade for the fifth consecutive year. Changes were observed in dissolved oxygen, which decreased from ‘very good’ to ‘good.’
Closer to the coast, water quality in the estuarine zone declined from ‘good’ to ‘moderate,’ continuing a gradual downward trend over the past four years.
Nutrient levels maintained an overall ‘good’ grade. Some local variation was observed, with dissolved inorganic nitrogen declining in the Ross Creek and Ross River, both shifting from ‘very good’ to ‘good.’ Louisa Creek remains out of balance, with a continued ‘very poor’ grade. In contrast, the Bohle River showed improvement in total phosphorus, which increased from ‘good’ to ‘very good,’ resulting in a ‘very good’ grade overall for nutrients.
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The overall decline in estuarine water quality was driven primarily by changes in physical-chemical conditions, which fell from ‘moderate’ to ‘poor.’ This was influenced by reduced water clarity, with turbidity grades decreasing from ‘good’ to ‘moderate’ in the Bohle River and Louisa Creek. More substantial declines were recorded in the Alligator Creek and Stuart Creek sub-basins, where turbidity dropped two grades, from ‘moderate’ to ‘very poor.’ Water movement, such as tides and waves, in Cleveland Bay may be playing a role. But so did the record-breaking rain, with high concentrations of sediment recorded flowing downstream.
The low dissolved oxygen levels seen in the freshwater zone, was also seen in the estuarine zone, with grades dropping from ‘good’ to ‘moderate’ in the Bohle River and Stuart Creek, while Alligator Creek dropped further to ‘poor.’
The Black Basin, which spans from the Black River in the south to Crystal Creek in the north, held onto its ‘good’ water quality grade in the freshwater zone for the seventh year in a row.
However, conditions varied across sub-basins, with the most notable changes observed in the Black River. Here, water quality declined to ‘poor’, the first time a sub-basin in the Black Basin has received this grade. This drop was driven by elevated nutrient levels. Unseasonal rainfall in August, followed by early wet season rains in November and December, washed sediment and nutrients from the catchment into the river. Further heavy rains in late January and early February added to this load. Runoff carries sediment from soil erosion, decaying organic matter and fertilisers downstream.
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Across the remaining sub-basins, water quality stayed within the ‘good’ rating, although some movement was seen in individual creeks.
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In the Bluewater Creek sub-basin, results were mixed. Althaus Creek showed improvements in both nutrient measurements (dissolved inorganic nitrogen – DIN and total phosphorus), while Bluewater Creek experienced a significant drop in DIN grades, falling from ‘moderate’ to ‘very poor.’ This was driven by a spike in nutrients at the beginning of the wet season, with elevated levels continuing after.
Changes in physical-chemical indicators were also apparent. Increased turbidity was recorded across all monitored sites in the Bluewater sub-basin, with Althaus Creek graded ‘very poor’ and Sleeper Log Creek ‘poor.’ Low dissolved oxygen continued to affect some creeks, with Ollera Creek remaining under pressure, although conditions improved slightly from ‘very poor’ to ‘poor.’ Rollingstone Creek showed relatively stable conditions, maintaining a ‘moderate’ grade for dissolved oxygen.
Black Basin estuarine zone maintained a ‘good’ water quality grade, with a notable increase in overall score.
Improvements were recorded across all sub-basins, with gains in both nutrient and physical-chemical indicators contributing to the stronger result.
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At Crystal Creek estuary, water quality improved from ‘moderate’ to ‘good,’ driven by a reduction in nutrient loads for both DIN and total phosphorus. Similar trends for DIN were seen elsewhere. Saltwater Creek recorded one of the largest gains, increasing from ‘moderate’ to ‘very good.’ Bluewater Creek was the exception, where the DIN score fell slightly.
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In the Bluewater Creek estuary, improvements were linked to changes in water clarity. Turbidity improved from ‘poor’ to ‘moderate,’ with the most significant change observed at Althaus Creek.
Here, turbidity increased from ‘very poor’ to ‘good’, the first time this site has not received a ‘very poor’ turbidity grade since the Report Card was first published.
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Improvements in the Rollingstone Creek estuary reflect a change in available data, with Camp Oven Creek no longer monitored.
Pesticides
Pesticides, including insecticides and herbicides, are used to manage pests and unwanted plants. Sampling occurs during the wet season, because heavy rainfall increases the risk of chemical runoff and pollutant loads entering our waterways. In the Townsville Dry Tropics, there are only two sites, one in each basin, that are monitored.
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This year, both sample sites saw a reduction in pesticide risk, though neither result changed the risk profile, which remains a ‘low’ risk at the Ross sampling site, and a ‘very low risk’ at the Black site.
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However, even if results show a ‘very low risk’, just detecting a pesticide can be concerning due to its toxicity and harmful effect on aquatic plants and animals.
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Different pesticides affect aquatic life differently too. A total of eight unique pesticides were detected at the Ross sampling site, two additional pesticides compared to the 2025 Tech Report. While in the Black, five pesticides were detected, a decrease from eight the year before. Knowing what’s in the water and at what levels helps us better understand impacts and what it could mean for the health of downstream ecosystems.
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With only two sampling locations, it is unknown if pesticides are a wider problem in the Townsville Dry Tropics.
