The main urban centre in the Tully Basin is the township of Tully, which is located inland and has a population of 2,436. Several localities, including Hull Heads, Tully Heads, and Mission Beach, are located on the coast.
The Tully Basin is steep in its upper areas which are primarily occupied by tropical rainforest and sclerophyll forests (largely in the Wet Tropics World Heritage Area), while the coastal floodplain has largely been cleared and drained for agricultural purposes.
Streams emerge from the coastal mountain range with high velocities and volumes resulting from rainfall events.
Koombooloomba Dam is located in the upper catchment and is used for power generation.
Wetlands listed in the Directory of (Nationally) Important Wetlands include Tully River-Murray River floodplains, Edmund Kennedy Wetlands and Licuala Palm Forest.
The Tully Basin has an area of 1,685 km2 and has a high proportion of natural/minimal use lands (75%). The remaining area is comprised of 12% sugarcane, 4% bananas, 5% grazing, 2% forestry, 1% other crops, 1% urban and 3% other land uses.
The Tully Basin grade has remained ‘good’ and the score increased from 61 to 72.
The diagram below shows the detailed results for each indicator by year. Click on the timeslider to see data from previous years.
The water quality grade for the Tully Basin remained ‘good’ and the score increased slightly from 68 in 2018-19 to 71.
Nutrients declined from ‘good’ with a score of 71 in 2018-19 to ‘moderate’ with a score of 60. Dissolved inorganic nitrogen (DIN) remained on a score of 42 with monthly median concentrations often not meeting guideline values. The filterable reactive phosphorus (FRP) indicator scored 77 and declined from ‘very good’ in 2018-19 to ‘good’, with monthly median concentrations often meeting guideline values.
Total suspended sediment (TSS), the indicator for sediment, scored 84, and improved to ‘very good’, with monthly median concentrations mostly meeting guideline values.
Pesticides for the Tully Basin remained ‘good’ and scored 70, equating to over 96 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 Euramo, capturing 86% of the basin.
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 Tully Basin habitat and hydrology index scored 56 for 2019-20 and the grade remained ‘good’.
The habitat modification score of 57 (‘moderate’) is comprised of the impoundment length score of 57 (‘moderate’) with 4.6 per cent of the total length of the waterways with a stream order of 3 or higher impounded by artificial structures. Koombooloomba Dam is the largest impoundment in the basin. The fish barrier indicator method is still being developed and will be available in future report cards.
Riparian extent for the Tully Basin scored 72 (‘good’) with 9% 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 17 (‘very poor’) with 57.8% loss of palustrine (freshwater) wetlands from pre-clear to 2017. Since 2013, an area of 6.6 hectares of palustrine wetlands has been lost. These results reflect a high level of historic loss due to development.
The invasive weeds indicator scored 71 (‘good’) in the Tully Basin and represents low impacts of aquatic weeds within the Tully freshwater system. The Tully Basin was the second highest scoring basin in the Wet Tropics for invasive weeds meaning that the impacts from aquatic weeds on waterway health is low for the region.
The Tully Basin flow indicator improved from ‘moderate’ in 2017-18 to ‘good’. Flows in the Tully Basin were not substantially altered from 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.
The freshwater fish assessment was conducted at 11 sites in the Tully Basin and the index grade was ‘very good’ with a score of 90.
A total of 36 species were caught and included 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 81 and was graded ‘very good’ meaning many native species expected to occur were frequently caught.
The indicator for introduced fish species scored 100 and was graded ‘very good’ due to very low numbers of alien species caught and no translocated fish species caught.