Johnstone Estuary

The area of the Johnstone estuary reporting zone can be defined by the pre-cleared extent of mangrove and saltmarsh remnant vegetation which is characterised by species that require periodic inundation of sea water. This area extends approximately 1.5 km north and 2 km south of the river mouth along the coastline and extends approximately 5.4 km inland.

The area includes numerous tributaries that drain into the main river channel. The assessment area of riparian extent extends further up the river than the mangrove and salt marsh communities to the upper tidal limit and includes vegetation types that are more typical of freshwater environments.

Land use within and adjacent to the Johnstone estuary area is dominated by residential and other urban developments and cropping. Urban development is associated with the town of Innisfail which overlays sections of the estuary area.

Key results for 2024-25

The Johnstone estuary grade has remained ‘good’ and the score increased from 61 to 63.

• Water quality remained ‘good’ with the score increasing from 67 to 73.
• Pesticide risk remained low and the grade remained ‘good’.
• Dissolved oxygen improved from ‘good’ to ‘very good’.
• Dissolved inorganic nitrogen (DIN) improved from ‘very poor’ to ‘poor’.
• FRP improved from ‘moderate’ to ‘good’.
• Mangrove and saltmarsh extent declined from ‘good’ to ‘moderate’ due to 0.1 km2 of recorded habitat loss since 2019.
• Shoreline mangrove habitat condition remained ‘good’ since the 2023-24 survey.
• Riparian vegetation extent remained ‘very poor’ with no recorded habitat loss since 2019.
• The flow indicator remained ‘good’ and the score remained 61.

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