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 improved from ‘moderate’ to 'good' with the score increasing from 57 to 61. 

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

Water quality

This is the second year that water quality for the Murray has been included. The grade remained ‘moderate’ and the score declined from 59 to 49. 

The sediment score, comprised of the total suspended solids (TSS) indicator, remained ‘good’ and the score declined slightly from 74 to 71, with monthly median concentrations of TSS often meeting guideline values.

The grade for nutrients declined from ‘good’ to ‘moderate’ and scored 50. The dissolved inorganic nitrogen (DIN) indicator declined from a score of 53 (‘moderate’) to 31 (‘poor’), with monthly median concentrations not meeting guideline values during high flows and sometimes meeting guideline values during base-flows. 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 27, equating to 83 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 four longer-term indicator categories that are updated every four years: wetland extent, (updated for 2017-18), riparian extent (to be updated for 2020-21), instream habitat modification consisting of impoundment length (updated for 2018-19) and fish barrier indicators (in development), and invasive weeds (updated for 2019-20).

The annual scores for the habitat and hydrology index from 2014-15, 2015-16, 2016-17 represent the changes resulting from the addition of indicators and not changes in the indicator scores themselves, whilst the index scores for 2017-18 to 2019-20 include annual updates to the flow indicator as well as updates to the longer term wetland extent, impoundment length and invasive weeds indicators. The Murray Basin habitat and hydrology index scored 55 for 2019-20 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 was impounded by artificial structures.

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 2019-20. Flows in the Murray Basin retained characteristics similar to modelled predevelopment flows in their capacity to support the key ecological assets of water holes, low flow spawning fish, riffle habitats and fisheries production.

The flow indicator provides scores for each flow assessment site and this can be used to assess flows at more local scales. More information on the results of the flow indicator is available in the results technical report.

Fish

The freshwater fish assessment was conducted at 13 sites in the Murray Basin and the index grade was ‘good’ with a score of 80.

A total of 32 species were caught and included one translocated species (Australian species that do not naturally occur in the waterway) and three alien species (species introduced into Australia) - the guppy (Poecilia reticulata), the platy (Xiphophorus maculatus) and spotted tilapia (Pelmatolapia mariae).

The indicator for species diversity scored 68 and was graded ‘good’ meaning native species expected to occur were frequently caught.

The indicator for introduced fish species scored 92 and was graded ‘very good’ due to the low numbers of alien and translocated fish species caught.

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