Johnstone Estuary

The area of the Johnstone 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 1.5 km north and 2 km south of the river mouth along the coastline and extends approximately 5.4 km inland. The area includes numerous tributaries that drain into the main river channel. 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 Johnstone estuary area is dominated by residential and other urban developments and cropping. Urban development is associated with the town of Innisfail which overlays sections of the estuary area.

Scroll down for further detailed results for each indicator group.

Grading

gradesa1

very good

gradesb1

good

gradesc1

moderate

gradesd1

poor

gradese1

very poor

insufficient data

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 2015-16 for the Johnstone estuary is ‘good’.

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 three monitoring sites the Johnstone River and one site in Ninds Creek.

The physical and chemical score of 29.5 (‘poor’) is comprised of a dissolved oxygen (DO) score of 29.5 (‘poor’) meaning that the annual median of DO concentrations did not comply with guideline values.

Nutrients scored 59.1 (‘moderate’) in the Johnstone estuary, comprising of a DIN (dissolved inorganic nitrogen) score of 50.4 (‘moderate’) and FRP (filterable reactive phosphorus) score of 68.2 (‘good’) meaning that the annual median of FRP concentrations complies with guideline values.

The chlorophyll a score in the Johnstone estuary was 90 (‘very good’) meaning that the annual median and at least 80% of the monthly medians of chlorophyll a concentrations comply with guideline values.

Using the ms-PAF method, pesticides received a ‘moderate’ risk category with 1.8% of species affected in the waterways of the Russell-Mulgrave estuary. This resulted in a pesticide grade of ‘good’ for the estuary.

Habitat and hydrology

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The overall habitat and hydrology grade for the Russell-Mulgrave estuary is ‘moderate’.

The mangrove and saltmarsh extent scored 63.7 (‘good’) with 13.7% 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. Riparian assessment therefore includes areas that have been cleared for agriculture and other developments. The riparian extent scored 9.5 (‘very poor’) with 77.3% loss from pre-clear to 2013.

Estuary fish barriers for the Johnstone estuary are scored 81 (‘very good’) and are graded 'very good’ for barrier density, ‘good’ for percentage of stream length to the first barrier, with an absence of low passability barriers (graded ‘very good’).

Estuary riparian extent, mangrove and saltmarsh extent and estuary fish barriers are updated every four years. The data for riparian extent, mangrove and saltmarsh extent is to be updated in 2018.

The method for the flow indicator is currently under development and will be available for future report cards.

Fish

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.