Mossman Basin

The Mossman Basin has an area of 479km2 with Mossman (~1,700 people) and Port Douglas (~3,200 people) being the major population centres. The basin consists of 76% natural/minimal use lands, 3% grazing, 10% sugarcane, 4% urban and 6% other land uses.

Steep mountains and hills dominate the Mossman Basin, with a narrow coastal plain which has been cleared and developed with agriculture (predominantly sugarcane) and urban land uses.

The Mossman Basin grade has remained ‘good’ and the score increased to 67 in 2017-18 from 63 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.

Water quality

Water quality reporting for the Mossman Basin commenced in 2017-18 with monitoring conducted by Douglas Shire Council at five sites located upstream and downstream of the Mossman River and South Mossman River confluence. Monitoring was not conducted during high flow events and consequently freshwater basin condition was assessed from base-flow water quality data only. Water quality scores are based on aquatic ecosystem guidelines for protection of freshwater systems, and are not based on load reduction targets for the marine environment.   

Water quality 2017-18 for the Mossman Basin scored 71 and was graded good’.  

The sediment score, comprised of the total suspended solids (TSS) indicator, was 76 (‘good’) with monthly median concentrations of TSS often meeting the guideline values.  

Nutrients were graded ‘good’ scoring 67, with dissolved inorganic nitrogen (DIN) graded ‘moderate’ and scoring 44 with monthly medians often not meeting guideline values, and filterable reactive phosphorus (FRP) graded ‘very good’ monthly median concentrations mostly meeting guideline values  

Pesticides were graded 'good' and scored 70, equating to 96.8 percent of species protected for the risk assessment metric.

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 2018-19), instream habitat modification consisting of impoundment length (to be 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 2017-18 includes the second year of reporting for the flow indicator and the updated wetland extent indicator. The Mossman Basin habitat and hydrology index scored 63 for 2017-18 and was graded ‘good’, remaining on the same score as the previous year.     

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. 

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

Riparian extent for the Mossman Basin scored 68 (‘good’) with 11.5% loss from pre-clear extent to 2013. It is expected the uplands would generally have better extent due to protected areas and less development. Less extent in the lowlands is due to development and land use. 

Wetland extent scored 16 (‘very poor’) with 60.7% loss of palustrine (freshwater) wetlands from pre-clear to 2017. An area of 0.6 hectares of palustrine wetlands was lost since 2013. These results reflect a high level of historic loss due to development. 

The invasive weeds indicator scored 36 (‘poor’) in the Mossman Basin and represents substantial impacts of aquatic weeds within the Mossman freshwater system including hymenachne (Hymenachne amplexicaulis), salvinia (Salvinia molesta), water hyacinth(Eichornia crassipes) and pond apple (Annona glabra).  

The Mossman Basin was graded as ‘very good’ for flows during 2017-18. Flows in the Mossman Basin were similar to pre-development flows in their capacity to support the key ecological assets of water holes, low flow spawning fish, riffle habitats and fisheries production. 


The fish index is currently being rolled out for the basins in the Wet Tropics and will be available for the Mossman Basin in upcoming report cards. 

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