Georges River Report Card 2023-2024

The overall ecological grade for the freshwater reaches was C+ in 2023-24 which is a slight drop from B- in 2021-22.

However, these results might not be a true reflection of the overall water quality, as unusual rainfall, such as what was experienced during the sampling period, has a significant impact on freshwater water quality since it brings sediments and pollutants from urban area.

Surprisingly, the most pristine bushland subcatchments at the headwaters (i.e., Upper Freshwater, O’Hares Creek, Lower Freshwater, Mill Creek and Woronora River subcatchments) were impacted with the overall grades reduced from good to fair. 

This is because although the largely forested areas had good riparian and water quality grades, the macroinvertebrate grades showed an overall drop this year. This decline can be attributed to the wet season, which washed these organisms downstream.

Similarly, the predominantly urbanised subcatchments (i.e., Bunbury Curran Creek, Cabramatta Creek, Prospect Creek and Lower Estuary subcatchments) showed a decline in water quality and riparian vegetation grades. This was probably caused by an increase in pollutants and nutrients being flushed from the urbanised area and entering the waterways during flooding and frequent rainfall events. The macroinvertebrate assemblage in the urban freshwater creeks subcatchments had low diversity and was mainly dominated by pollution-tolerant species like snails and worms.

The overall estuary grade improved to A- this year from B in 2021-22. The improvement can be attributed to lower turbidity during sampling. This year’s estuary sampling coincided with limited rainfall resulting in generally good grades. The lower sections of the estuary are regularly flushed by tidal movement, particularly within the main channel and have received excellent grades. 

Further up the river some bays experience less tidal flushing and are known as dead water areas. In the past these shallow, muddy bays which include sampling sites such as Gungah and Bonnet Bays have typically received a lower grade. In the upper sections, the estuary has reduced tidal flushing and is more impacted by pulses of stormwater from the urbanised catchment.