Wetlands that reduce stormwater pollutant concentrations and are sustainable in an urban context

It is well recognised the development of natural landscapes into a standard urban residential development will increase the pollutant concentrations discharging into the receiving waterway system. Pollutant concentrations that have been recorded and shown to increase include suspended solids, nutrients (such as total nitrogen and total phosphorous), faecal coliforms, and algae levels. A number of engineered Stormwater Quality Improvement Devices (SQIDs) in recent years have been implemented to attempt to improve the water quality as part of developing Water Sensitive Urban Design (WSUD), including wetlands. Some published reports indicate that wetlands may actually be worsening water quality. Lawson and Treloar has been involved in a number of urban developments that have included SQIDs in the form of constructed wetlands to improve the water quality as part of their WSUD. From the long term and event water quality monitoring program for two particular constructed wetlands it is possible to indicate the acceptable performance of these wetlands. This paper will discuss, for each wetland, the overall layout, the type of water quality monitoring conducted and the results from the monitoring programs. These monitoring programs have indicated that for the two wetlands considered in terms of the concentrations that are entering the wetlands and are discharged from the wetlands that an improvement in the water quality is occurring effectively.