Wetlands in the Torrens and Patawolonga Catchments
A brief history
It is estimated that 70% of wetlands in South Australia have been destroyed since European settlement. Natural wetlands were once a significant component of fresh water environments across the Adelaide Plains. Before European settlement swamps and marsh areas (known as the Reed Beds), once spanned an area from Glenelg to Port Adelaide. Water travelling down the River Torrens was filtered through the Reed Beds before dispersing north into the Port River or south into the Patawalonga and the sea. These areas were altered during the early 1900's when many natural wetlands were filled in to create dry land for housing, and water flows were redirected through constructed channels and drains.
Urban development, such as the construction of roads, houses, car parks, shopping centres and businesses, has increased the amount of stormwater runoff in our cities and suburbs. Hard surfaces absorb very little rainfall so stormwater gutters, channels and drains were developed to move stormwater runoff as quickly as possible from our neighbourhoods to rivers and the sea. As a result, pollutants such as litter, nutrients, faeces, silt, dirt, oil, and leaf litter flows unfiltered into the Patawalonga, Torrens and Port rivers and Gulf St Vincent.
THE LOWER TORRENS BEFORE URBAN DEVELOPMENT
Urban wetlands
As we have developed a greater understanding of the importance of wetland environments and the roles they can play in urban areas, catchment water management boards and local councils have worked together to construct and conserve urban wetlands. Artificial wetlands provide solutions to a number of water issues including flood control and stormwater pollution management. Urban wetlands beautify urban areas and also provide habitat and safe havens for native animals and plants.
Urban wetlands have been constructed throughout metropolitan Adelaide to improve the quality of urban runoff (stormwater). Wetlands retain this stormwater for long periods of time so that natural filtering processes can occur before it is released back into rivers and stormwater drains. For example, the water flowing through the Warriparinga wetland is diverted from the Sturt River . It is retained in the wetland for approximately ten days before being released into the Sturt drain which carries it to the Patawalonga Lake . Stormwater that has travelled through a wetland is much cleaner. Wetlands improve water quality by processes such as sedimentation, nutrient uptake and the destruction of pathogens through ultraviolet radiation.
To find out more go to: How Does A Wetland Work?
Wetlands and Mosquitoes
Urban wetlands are widely appreciated for their role in improving water quality and providing habitat and sanctuary for wildlife. Most urban wetlands are accessible to the public and enjoyed as areas for recreation and relaxation. However, not all local residents have been enthusiastic about the construction of an urban wetland in their area. Their opposition relates to a concern that wetlands can attract nuisance pests, such as mosquitoes, and the associated diseases.
It is a common misconception that wetlands harbour large populations of mosquitoes. A well designed wetland does not provide ideal conditions for mosquitoes. Mosquitoes prefer still waters for breeding, but well designed urban wetlands are constructed to slow the flow of water, not stop it all together. Successful urban wetlands provide habitats for insects and other animals which feed on mosquito larvae, so mosquito populations are kept in balance.