Hinchinbrook Channel

The area of the Hinchinbrook Channel 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 includes the length of the channel (approximately 45 km) and extends due south along the coastline from the southern mouth of the channel for approximately 20 km, the area also extends west on the mainland for approximately 10 km and east on Hinchinbrook Island for approximately 6 km. The area has numerous coastal tributaries that drain into the channel from the mainland and from Hinchinbrook Island. The assessment area of riparian extent extends upstream of the Herbert River further than the mangrove and salt marsh communities to the upper tidal limit and includes vegetation types that are more typical of freshwater environments. On Hinchinbrook Island the estuary area is all within National Park. The estuary area on the mainland is predominantly conservation use (Girrigun National Park) whilst land uses in the area include forestry and pond aquaculture with some cropping and residential development in the southern reaches on the mainland around the Herbert River. The towns of Cardwell, located at the north of the channel, and Ingham, located to the south of the channel are both on the mainland. The Hinchinbrook Channel is listed in the Directory of (Nationally) Important Wetlands.

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 Hinchinbrook Channel is ‘very 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 in the Hinchinbrook Channel.

The physical and chemical score of 75.3 (‘good’) is comprised of a dissolved oxygen (DO) score of 76.4 (‘good’) and a turbidity score of 74.3 (‘good’) meaning that the annual medians of DO concentrations and turbidity comply with guideline values.

Nutrients scored 90.0 (‘very good’) in Hinchinbrook Channel, comprising of a DIN (dissolved inorganic nitrogen) score of 90.0 (‘very good’) and FRP (filterable reactive phosphorus) score of 90.0 (‘very good’) meaning that the annual median and at least 80% of monthly medians of DIN and FRP concentrations comply with guideline values.

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

Pesticides are not monitored in Hinchinbrook Channel therefore a score and grade cannot be provided.

Habitat and hydrology

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The overall habitat and hydrology grade for the Hinchinbrook Channel estuary is ‘good’.

The mangrove and saltmarsh extent scored 84.3 (‘very good’) with 4.1% loss from pre-clear to 2013. These results reflect a low level of development within the estuary area. 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 51.8 (‘moderate’) with 21.9% loss from pre-clear to 2013.

Estuary fish barriers for the Hinchinbrook Channel are scored 80 (‘good’) and are graded 'very good’ for barrier density, ‘poor’ for percentage of stream length to the first barrier, and there is 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.

Although seagrass habitat occurs in Hinchinbrook Channel there is currently no seagrass monitoring in the estuary and a seagrass grade and score is not available.

The method for the flow indicator is 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.