Herbert Basin

In the upper catchment of the Herbert Basin the main towns are Herberton (population 934) and Ravenshoe (population 1,442), which are located on the Atherton and Evelyn Tablelands.

The largest town in the Herbert Basin is Ingham, located in the lower catchment, with a population of 4,767.

The Herbert River starts 8km north-east of the town of Herberton and winds 340 km to its mouth 7km north of Halifax. Due to its diversity of landform and social communities, the basin is most easily divided into three sections.

The upper basin consists of the vast north-western section upstream of the Herbert River Falls and forms the most southern extent of the Atherton and Evelyn Tablelands. This area is highly utilised for cropping, especially potatoes and hay. The area closer to Innot Hot Springs is undergoing an expansion of cane, and dairy is continually reducing. There are also extensive grazing areas in the western area of the upper catchment – and much of the area was subject to historic alluvial tin mining.

The intermediate basin includes the Herbert River Gorge and consists mostly of National Parks, State Forests and other State Land, some within the Wet Tropics World Heritage Area.

The lower basin is the river delta or floodplain, and is characterised by alluvial soils and regular inundation from flooding. Many of the streams and tributaries discharge directly into Halifax Bay. The lower catchment is dominated by sugarcane and there is some irrigation in the southern-most area of the catchment.

The Herbert Basin has an area of 9,842 km2 and consists of 27% natural/minimal use lands, 56% grazing, 8% sugarcane, 4% forestry and 4% other land uses.

The grade for the Herbert Basin has improved this year from ‘moderate’ to 'good' with the score increasing from 59 to 71. 

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

Water quality

The water quality grade for the Herbert Basin remained ‘good’ and the score increased from 61 in 2018-19 to 73.

Nutrients improved from ‘moderate’ to ‘good’ with the score increasing slightly from 59 in 2018-19 to 61. Dissolved inorganic nitrogen (DIN) scored the lowest (46) and was graded ‘moderate’, with monthly median concentrations often not meeting guideline values. The filterable reactive phosphorus (FRP) indicator scored 76 and remained ‘good’, with monthly median concentrations often meeting guideline values.

Total suspended solids (TSS), the indicator for sediment, scored 90 and the ‘very good’ grade was unchanged from 2018-19, with most monthly median concentrations meeting guideline values.

Pesticides for the Herbert Basin remained ‘good’ and scored 68, 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 Ingham, capturing 87% 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 Herbert Basin habitat and hydrology index scored 56 for 2019-20 and the grade remained ‘moderate’.

The habitat modification score of 92 (‘very good’) is comprised of an impoundment length score of 92 (‘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 Herbert Basin scored 85 (‘very good’) with 3.9% 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 20 (‘very poor’) with 51.9% loss of palustrine (freshwater) wetlands from pre-clear to 2017. Since 2013, 31.6 hectares of palustrine wetlands have been lost. These results include a high level of historic loss due to development.

The invasive weeds indicator scored 19 (‘very poor’) in the Herbert Basin and represents major impacts of aquatic weeds within the Herbert freshwater system. The Herbert Basin was the second 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 Herbert Basin grade for flow remained ‘good’. Flows at most assessment sites in the Herbert 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 28 sites in the Herbert Basin and the index grade was ‘very good’ with a score of 85.

A total of 41 species were caught and included three translocated species (Australian species that do not naturally occur in the waterway) and five alien species (species introduced into Australia) - the guppy (Poecilia reticulata), the swordtail (Xiphophorus helleri), the platy (Xiphophorus maculatus), gambusia (Gambusia holbrooki) and Mozambique tilapia (Oreochromis mossambicus).

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 88 and was graded ‘very good’ due to 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.