Mulgrave Basin

The Mulgrave basin contains the largest population centres in the region. At the northern end of the basin are the city of Cairns (population in excess of 170,000) and the Trinity Inlet. The Indigenous Yarrabah community with a population of approximately 3000 people is located on the coast to the east of Cairns. The Port of Cairns occupies the lower end of Trinity Inlet and provides limited deep-water ship berthing.

The upper catchment is in the relatively undisturbed rainforest environments of the Bellenden Ker Range. A small portion of the upper Mulgrave is on the edge of the developed agricultural area of the Atherton Tableland. The river floodplains and the lower river valley are dominated by sugarcane where the environment has been significantly modified with the loss of much of the original lowland rainforest.



The overall grade for the Mulgrave basin is moderate (C). Water quality and habitat and hydrology contributed to this grade.

Scroll down for further detailed results for each indicator group.



very good








very poor


insufficient data


not applicable

Confidence surrounding the data used in the circle diagrams has been assessed using a multi-criteria framework.


Water quality

Hover over each segment for indicator scores and data confidence.

The overall water quality grade in 2014/15 for the Mulgrave basin is ‘moderate’.

Water quality grades are based on aquatic ecosystem guidelines for protection of freshwater systems, and are not based on load reduction targets for the marine environment. The results are derived from the end of catchment monitoring site at Deeral, capturing 59 per cent of the basin.

The sediment score of 100 (Very Good) is comprised of a TSS score of 100 (Very Good) indicating that more than 80 per cent of the monthly medians of TSS meet guideline levels.

Nutrients scored 82.79 (Moderate) in the Mulgrave basin, comprising of a DIN (Dissolved Inorganic Nitrogen) score of 72.88 (Moderate) and FRP (Filterable Reactive Phosphorus) score of 92.69 (Moderate).

Using the ms-PAF method, contaminants received a low risk category with 3.97 per cent of species affected in the waterways of the Mulgrave basin. This resulted in a contaminant grade of good for the basin.

Habitat and hydrology

Hover over each segment for indicator scores and data confidence.

The overall habitat and hydrology grade for the Mulgrave basin in 2014/15 is ‘moderate’.

The habitat modification score of 100 (very good) is comprised of an impoundment length score of 100 (very good) indicating that less than 1 per cent of the total length of the waterway are impounded by artificial structures. The fish barrier indicator method is still being developed and will be available in future report cards.

Riparian extent for the Mulgrave basin scored 100 (good) with 6.1 per cent loss from pre-clear extent to 2013. With the basin predominantly rainforest in the upper and midlands, it is expected that the majority of loss is in the lowlands due to development and land use.
Wetland extent scored 32.7 (very poor) with 36.2 per cent loss of palustrine (freshwater) wetlands from pre-clear to 2013. These results reflect a high level of historic loss due to development. Wetland losses in future reporting periods will be minimal.

Freshwater riparian extent and wetland extent are updated every four years and the figures in the pilot report card are the most current. The data for both are due to be updated in 2017/18.

The methods for the flow and invasive weeds indicators are currently underdeveloped and will be available for future report cards.


Hover over each segment for indicator scores and data confidence.

The fish index is currently under development and will be available in future report cards.

Further information on the methods used to produce the scores and grades and detailed results can be found here.