The ecological degradation of the Georges River is consistent with the worldwide phenomena known as the ‘Urban Stream Syndrome’. This syndrome occurs when impermeable urban landscapes deliver much larger volumes of stormwater to the river than natural green areas would deliver. Creeks begin to function as stormwater canals, flushing polluted water into the river. Other conditions that often accompany this syndrome include sewage overflows, litter pollution, widespread weeds, erosion and flooding. These, and the many other ongoing challenges for the river, are a result the urbanised nature of the catchment.
Deforestation and habitat loss
Much of the Georges River catchment is highly urbanised, with the clearing of significant areas of native forest resulting in loss of habitats and reduced biodiversity. Cleared landscapes lack the ability to trap and filter pollutants before they flow into waterways. Large-scale sandmining and dredging have also dramatically altered the morphology of the Georges River.
High stormwater flows
Impervious urban surfaces prevent infiltration of water into the ground, as occurs in forested landscapes, which filters and cleans the water before circulating back into the waterway. Most runoff from storms in the catchment is directed into stormwater channels and urban creeks, then into the Georges River. The resulting large and fast flows wash many pollutants into waterways, erode creeklines and flood low-lying areas.
Poor water quality
Rainwater flowing across urban landscapes can pick up oils, detergents and tyre residue from roads; fertilisers, pesticides and lawn clippings from gardens; sediment from poorly maintained construction sites; litter; and other pollutants carelessly disposed of down outdoor drains. Most stormwater is not treated before entering the Georges River.
Sewage leaks and overflows occur from broken pipes and blockages, and when high flows overwhelm the system during high rainfall. As well as smelling awful, sewage leaks contain pathogens that are harmful to human health, and high nutrient concentrations that can result in fish kills and algal blooms.
Litter is washed or blown into waterways, including creeks, rivers and the ocean. Much of the litter entering the Georges River that is plastic does not degrade, it just breaks up into small pieces that persist in the environment. Plastic litter reduces amenity, harms wildlife and can enter food webs.
Some introduced plants and animals thrive in highly altered urban landscapes, with highly diverse native ecosystems being replaced by a few hardy exotic species. In addition to the loss of native biodiversity, simplified ecosystems do not provide the same range of beneficial ecosystem services as more complex ecosystems.
Climate change is a global phenomenon with local consequences. Changing climatic conditions will require adjustments in our way of life and threaten many species’ survival. Reduced rainfall, more intense storms, sea level rise and flooding will have significant impacts on property and life in the Georges River catchment.
The Georges River catchment has over 1.4 million residents. Most people value maintaining clean and healthy waterways for their intrinsic natural values, beauty and amenity. However, a large urban population that feels increasingly disconnected from nature can lose sight of how their actions can affect river health.