Barron Estuary

The area of the Barron estuary reporting zone can be defined by the pre-cleared extent of mangrove and saltmarsh remnant vegetation which is characterised by species that require periodic inundation of sea water.

This area extends approximately 10.5 km north and 4.5 km south of the river mouth along the coastline and extends approximately 5.5 km inland. The area includes several tributaries that drain into the Barron River and coastal streams that drain directly into the sea.

The assessment area of riparian extent extends further up the river than the mangrove and salt marsh communities to the upper tidal limit and includes vegetation types that are more typical of freshwater environments.

Land use within and adjacent to the Barron estuary area is dominated by urban development. The northern beach suburbs of Machans Beach, Yorkeys Knob and Holloways beach, and the Cairns suburbs of Aeroglen, Cairns North and Whitfield overlay the estuary area. Industries within the estuary area include the Cairns international and domestic airport, quarries, aquaculture and sugarcane.

Scroll down for further detailed results for each indicator group.

Grading

gradesa1

very good

gradesb1

good

gradesc1

moderate

gradesd1

poor

gradese1

very poor

gradesnd1

insufficient data

gradesna1

not applicable

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

confidence

Water quality

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

Water quality grades are based on aquatic ecosystem guidelines for protection of estuarine waters, and are not based on load reduction targets for the marine environment. The results are derived from a transect of five monitoring sites in the channel of the Barron River.

The physical and chemical score of 100 (very good) is comprised of a dissolved oxygen (DO) score of 100 (very good) indicating the annual median and 80 per cent of the monthly medians of DO comply with guideline values.

Nutrients scored 78.1 (moderate) in the Barron estuary, comprising of a DIN (dissolved inorganic nitrogen) score of 84.1 (moderate) and FRP (filterable reactive phosphorus) score of 72 (moderate).

The chlorophyll a score in the Barron estuary was 81.0 (moderate).

Habitat and hydrology

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The overall habitat and hydrology grade for the Barron estuary could not be determined due to insufficient data. The development of the flow and fish barrier indicators will provide sufficient data for habitat and hydrology to be reported for the Barron estuary in future report cards.

The mangrove and saltmarsh extent scored 28.7 (very poor) with 31.1 per cent loss from pre-clear to 2013. Riparian extent is assessed to the upper tidal limit of the river which extends upstream of the estuary area that is characterised by mangroves and saltmarsh. The riparian extent scored 26.5 (Very poor) with 48.3 per cent loss from pre-clear to 2013. These results reflect the high level of development within the estuary area.

The low mangrove and saltmarsh extent and riparian extent scores for the Barron are mostly the result of historic extensive clearing activity. More recently mangrove communities in the Barron estuary have been effectively managed to ensure there has been no major new clearing and to allow for some revegetation.

Estuary riparian extent and mangrove and saltmarsh 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 fish barrier indicators are currently under development and will be available for future report cards.

Fish

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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.