Johnstone Basin

The Johnstone basin population is 15,000 and largely concentrated within the towns of Innisfail, Malanda, Millaa Millaa and South Johnstone.

The two key tributaries of the Johnstone River include the North Johnstone and South Johnstone Rivers. The North Johnstone River basin can loosely be divided into three sections.

The upper river is a ‘mixed land use’ area consisting of dairy, beef grazing, sugar cane, horticulture (potatoes) and the townships of Millaa Millaa and Malanda.

The middle section contains steep forested areas, much of which is in the Wet Tropics World Heritage Area.

The lower reaches are characterised by low sloping hills and coastal floodplains, which contain a majority of the agricultural areas including the larger townships of Innisfail and South Johnstone.

The Johnstone basin has an area of 2,326 km2 and has a relatively high proportion of natural/minimal use lands (55%). The remaining area contains 16% grazing, 12% sugarcane, 6% dairy (in the upper catchment), 3% bananas, 1% other crops, 2% urban 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

Water quality in the Johnstone basin remained ‘good’ with the score decreasing from 79 in 2015-16 to 73.

The filterable reactive phosphorus (FRP) indicator scored the lowest (57) and was graded ‘moderate’, meaning that median monthly concentrations sometimes did not meet guideline values.

Dissolved inorganic nitrogen (DIN) scored 70 and was graded ‘good’, with monthly median concentrations often meeting guideline values.

Total suspend sediment (TSS), the indicator for sediment, scored 81 and was 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 Johnstone 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. Except for pesticides the results are derived from two end of catchment monitoring sites at Goondi and Central Mill, capturing 58% of the basin. Pesticide results are derived from the Coquette Point monitoring sites, capturing 70% 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 Johnstone basin (reported annually) was introduced in 2016-17.

Changes in the habitat and hydrology index scores over the last three years are as a result of the addition of indicators rather than changes in the indicator scores themselves.

The habitat and hydrology index increased from ‘moderate’ in 2015-16 to ‘good’ with the score rising from 57 to 65 due to the addition of the flow indicator.

The habitat modification score of 98 (‘very good’) is comprised of an impoundment length score of 98 (‘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 Johnstone basin scored 74 (‘good’) with 8.1% 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 26 (‘poor’) with 44.3% 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 29 (‘poor’) in the Johnstone basin and represents substantial impacts of aquatic weeds within the Johnstone freshwater system, including hymenachne (Hymenachne amplexicaulis), salvinia (Salvinia molesta), and pond apple (Annona glabra).

The Johnstone basin was graded as ‘very good’ for flows during 2016-17. Flows in the Johnstone basin were similar to 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 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.