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 diagram below shows the detailed results for each indicator by year. Click on the timeslider to see data from previous years.
Water quality in the Herbert basin remained 'good' in 2016-17 with the score decreasing from 80 in 2015-16 to 76.
Dissolved inorganic nitrogen (DIN) scored the lowest (44) and was graded ‘moderate’, with monthly median concentrations often not meeting guideline values. The filterable reactive phosphorus (FRP) indicator and total suspended solids (TSS), the indicator for sediment, both scored 90 and were graded ‘very good’, with most monthly median concentrations meeting guideline values.
Using the ms-PAF method, pesticides received a low risk category, with 97.5 % of species protected in the waterways of the Herbert Basin. This resulted in a pesticide grade of ‘good’ for the basin.
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, riparian extent (both to be updated for 2017-18), invasive weeds (to be updated for 2019-20), habitat modification (impoundment length (to be updated for 2018-19) and fish barrier indicators (in development)). The flow indicator for the Herbert basin (reported annually) was introduced in 2016-17.
Changes in the habitat and hydrology index scores over the last three years are a result of the addition of indicators rather than changes in the indicator scores themselves.
The habitat and hydrology index remained ‘moderate’ in 2015-16, with the score rising from 54 to 56 due to the addition of the flow indicator.
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 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 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 51.1% loss of palustrine (freshwater) wetlands from pre-clear to 2013. These results reflect a high level of historic loss due to development. Wetland losses in future reporting periods will be minimal.
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 was graded as ‘good’ for flows during 2016-17. Flows in the Herbert basin were not substantially altered from 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 fish index is currently under development and will be available in future report cards.
Further information on the methods used to produce the scores and grades and detailed results can be found here.