Abstract
This study investigated the catchment of an urban wetland on sandy soils in Western Australia. The wetland is of high conservation value but is currently used as a stormwater-compensating basin. The main aims of this work were to: determine the importance of stormwater drains in the water and pollutant balance of the lake and to evaluate pollutant retention rates by the wetland. When compared to water-quality guidelines for receiving waters, only pH and conductivity met the recommended criteria. Background flows contributed significantly to the pollutant load. More than 85% of total suspended solids, nutrients and heavy metals were retained by the wetland. An evaluation of the performance of the lake as a pollutant sink, identified phosphorus as the pollutant that requires the largest surface area for treatment. With the continuing trend of urban infill ? which aims to increase development density, especially in housing ? the percentage of impervious surfaces in the catchment will rise to over 50% within the next decade. Residential areas of medium-to-high density will most likely present the greatest challenge for managing the quality of urban runoff.