Wetlands and Ponds for Stormwater Treatment in Subtropical Australia: Their Effectiveness in Enhancing Biodiversity and Improving Water Quality?

Abstract

Stormwater best management practice is aimed at reducing potential downstream impacts on aquatic ecosystem health. Sediment basins, wetlands and ponds are commonly used in subtropical Australia for water-quality improvement; they also have the potential to enhance aquatic biodiversity in urbanised catchments. Two retrofit field sites in Brisbane, Australia were monitored for water quality and ecosystem health. The Golden Pond “wetland system” treatment train consisted of a sediment basin and two wetlands. The Bridgewater Creek “pond system”, consisted of a sediment basin and five ponds. Suspended solids were reduced during wet weather, but increased during dry weather due to resuspension by ducks. NO3-N decreased in both wet and dry weather. NH4-N increased probably due to ammonification of organic matter. PO4-P decreased. The removal of soluble NO3 and PO4 is indicative of biological uptake by phytoplankton submerged pond weeds and periphyton attached to aquatic macrophytes. Macroinvertebrate species richness increased, and mosquitoes were not a problem due to predation of larvae by macroinvertebrates. Macrophyte survival was adversely affected by flash flooding and increased inundation. Although water quality objectives were not consistently achieved, both systems were effective in reducing suspended solids and nutrients from stormwater runoff and provided a habitat for aquatic organisms.