The area of the Russell-Mulgrave 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 5.2 km inland. The area includes the confluence of the Russell River and Mulgrave River and several coastal tributaries that drain into the main river channels.
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 Russell-Mulgrave estuary area is dominated by grazing in native vegetation in the downstream reaches with cropping more dominant upstream of the confluence on both the Russell and Mulgrave rivers, with some residential development. The localities of Deeral and Bellenden Ker are just west of the estuary area.
The diagram below shows the detailed results for each indicator by year. Click on the timeslider to see data from previous years.
Water quality in the Russell-Mulgrave estuary remained ‘good’ with the score decreasing slightly from 77 to 75 since 2015-16.
The lowest scoring indicator was DIN (dissolved inorganic nitrogen) at 51 (‘moderate’). FRP (filterable reactive phosphorus) and pesticides were graded ‘good’ and all other indicators were graded ‘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 two monitoring sites in the channel at the confluence of the rivers.
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 (update due for 2017-18), riparian extent (update due for 2017-18) and fish barriers (update due for 2019-20).
The habitat and hydrology index for the Russell-Mulgrave has increased from 67 in 2015-16 to 69 (both years graded ‘good’). The change is due to the addition of the flow indicator.
The mangrove and saltmarsh extent scored 98.0 (‘very good’) with 0.5% 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 24 (‘poor’) with 46.8% loss from pre-clear to 2013.
Estuary fish barriers for the Russell-Mulgrave estuary are scored 81 (‘very good’) and are graded 'very good’ for barrier density, ‘good’ for percentage of stream length to the first barrier and 'very good' for an absence of low passability barriers.
The Russell-Mulgrave estuary was graded as ‘good’ for flows during 2016-17. A single hydrological measure (duration of medium flows) was markedly altered from predevelopment flows and this occurred for the Peets Bridge flow assessment site on the Mulgrave River scoring a 1 out of a possible 5.
More information on the results of the flow indicator is available in the results technical report.
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.