The area of the Daintree 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 5.5 km northeast and 6.4 km south-west of the river mouth along the coastline and extends approximately 12 km inland.
The area includes several coastal tributaries that drain into the Daintree River. 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 Daintree estuary area is dominated by cropping with some grazing and residential development. The Daintree village is approximately 16 km north-west of the river mouth. The lower Daintree River is listed in the Directory of (Nationally) Important Wetlands.
The Daintree estuary grade has remained ‘good’ and the score decreased slightly from 72 to 70 since the previous year.
The diagram below shows the detailed results for each indicator by year. Click on the timeslider to see data from previous years.
The Daintree estuary water quality was graded ‘very good’ and the score increased from 80 in 2017-18 to 81.
The lowest scoring indicators remained Turbidity (71) and DIN (dissolved inorganic nitrogen) (76) and both were graded ‘good’ along with chlorophyll a, with monthly median values often meeting guideline values.
Filterable reactive phosphorus (FRP)and dissolved oxygen (DO) were graded ‘very good’ with most monthly median values meeting guideline values.
Pesticides were graded “very good” and scored 90, equating to over 99 percent of species protected for the risk assessment metric.
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 for all indicators excluding pesticides were derived from a transect of three monitoring sites in the channel of the Daintree River. The pesticide monitoring was conducted at the Lower Daintree Great Barrier Reef Catchment Loads Monitoring Program site.
Habitat and hydrology
The habitat and hydrology index is comprised of three longer-term indicator categories that are updated every four years: mangrove and saltmarsh extent, riparian extent (both updated for 2018-19) and fish barriers (update due for 2019-20). The habitat and hydrology score has remained 60 (graded ‘moderate’).
The mangrove and saltmarsh extent scored 93 (‘very good’) with 1.7% loss from pre-clear to 2017. There was no change in extent between the previous assessment for 2013 and the updated assessment for 2017. 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 25 (‘poor’) with 42.4% loss from pre-clear to 2017. There was no change between the previous assessment for 2013 and the updated assessment for 2017, however the updated Regional Ecosystem mapping (Version 5) resulted in a 2.7% reduction of the estimated loss of riparian extent from pre-clear which was set at 45.1% for 2013.
For estuary fish barriers the Daintree estuary scored 61 (‘good’) with ‘moderate’ barrier density, ‘moderate’ percentage of stream length to the first barrier and an absence of low passability barriers (graded ‘very good’).
The flow indicator could not be assessed for the Daintree estuary due to the lack of pre-development modelled flow, which is required for the analysis.
The fish index is currently under development and will be available in future report cards.