Murray Basin

The main town centre in the Murray Basin is Cardwell which is located on the coast opposite Hinchinbrook Island and has a population of 1,176. There are several other localities including Kennedy, Bilyana and Carruchan, mainly located near the centre of the basin.

The Murray Basin varies from steep rainforest-covered mountains in the west, to a low-relief floodplain mostly developed for agriculture in the centre, with further remnant forest near the coast.

Major waterways include the Murray River, Dallachy Creek, Meunga Creek and Kennedy Creek, and numerous smaller coastal creeks drain into Hinchinbrook Channel. The sub-catchments discharge into several wetlands included in the Directory of (Nationally) Important Wetlands, and which include declared Queensland Fish Habitat Areas, seagrass meadows, and areas within the Great Barrier Reef World Heritage Area.

The Murray Basin has an area of 1,115 km2 and also has a high proportion of natural/minimal use lands (64%). The remaining area is comprised of 14% sugarcane, 10% forestry, 6% grazing, 1% bananas, 1% other crops, 1% urban and 4% other land uses.

The Murray Basin grade has remained ‘moderate’ and the score decreased from 59 to 57 since the previous year. This is the first year that water quality has been included for the Murray Basin.

The diagram below shows the detailed results for each indicator by year. Click on the timeslider to see data from previous years.

Water quality

Water quality in 2018-19 for the Mulgrave Basin was graded ‘moderate’ with a score of 59.

The sediment score, comprised of the total suspended solids (TSS) indicator, scored 74 (‘good’) with monthly median concentrations of TSS often meeting guideline values.

The grade for nutrients was ‘good’ and scored 65. The dissolved inorganic nitrogen (DIN) indicator was ‘moderate’ and scored 53, with some monthly median concentrations meeting guideline values. Filterable reactive phosphorus (FRP) was ‘good’ and scored 77, with monthly median concentrations often meeting guideline values.

Pesticides for the Murray Basin were graded ‘poor’ and scored 25, equating to 82 percent of species protected for the risk assessment metric.

Water quality grades are based on aquatic ecosystem guidelines for protection of freshwater systems and are not based on load reduction targets for the marine environment. The results are derived from the end of catchment monitoring site at Bilyana.

Habitat and hydrology

The habitat and hydrology index is comprised of the flow indicator category (updated annually) and four longer-term indicator categories that are updated every four years: wetland extent, (updated for 2017-18), riparian extent (to be updated for 2019-20), instream habitat modification consisting of impoundment length (updated for 2018-19) and fish barrier indicators (in development), and invasive weeds (to be updated for 2019-20).

The annual scores for habitat and hydrology index for 2015-16 and 2016-17 represented changes due to the addition of the invasive weeds and flow indicators, respectively, and not changes in the indicator scores themselves. The index score for 2018-19 includes the third year of reporting for the flow indicator. The Murray Basin habitat and hydrology index scored 56 for 2018-19 and the grade remained ‘moderate’.

The habitat modification score of 100 (‘very good’) is comprised of an impoundment length score of 100 (‘very good’) indicating that less than 1% of the total length of the waterways with a stream order of 3 or higher are impounded by artificial structures. There was no change in impoundment length score for the 2018-19 assessment.

The fish barrier indicator method is still being developed and will be available in future report cards.

Riparian extent for the Murray Basin scored 75 (‘good’) with 7.8% loss from pre-clear extent to 2013. It is expected that the majority of loss is in the lowlands due to development and land use.

Wetland extent scored 19 (‘very poor’) with 53.5% loss of palustrine (freshwater) wetlands from pre-clear to 2017. Since 2013, 37.3 hectares of palustrine wetlands has been lost. These results include a high level of historic loss due to development.

The invasive weeds indicator scored 19 (‘very poor’) and represents major impacts of aquatic weeds within the Murray freshwater system. The Murray Basin was the lowest scoring basin in the Wet Tropics, with impacts from aquatic weeds including hymenachne (Hymenachne amplexicaulis), salvinia (Salvinia molesta), water hyacinth (Eichornia crassipes) and pond apple (Annona glabra).

The Murray Basin remained ‘good’ for flows during 2018-19. Flows in the Murray Basin retained characteristics similar to modelled pre-development flows in their capacity to support the key ecological assets of water holes, low flow spawning fish, riffle habitats and fisheries production.

Fish

The fish index is currently being rolled out for the basins in the Wet Tropics and will be available for the Murray Basin next year. 

See the detailed reports for further information on the methods used to produce the scores and grades and detailed results