Assessment of the Ecological and Hydrological Impacts of Stormwater Harvesting on a Constructed Wetland

Abstract

Although the vegetation within constructed stormwater wetlands plays an important role in the treatment processes taking place, its density and distribution depends on the wetland bathymetry and the imposed hydrologic regime. This paper describes an ecological and hydrological assessment of a constructed stormwater treatment wetland. A continuous simulation hydrologic model of the urban catchment and the wetland system is employed. The study also includes a site monitoring program of vegetation and ecosystem characteristics within both the wetland and the upstream and downstream sections of the urban stream system. The hydrological analysis of the system has been used to investigate the impact of the hydrologic regime on the ecosystem. The model is also used to investigate rainwater harvesting within the catchment and stormwater harvesting from the wetland. The study has shown that the wetland provides significant interception of rainfall, which is linked to the improved ecosystem characteristics observed in the stream system downstream of the wetland. Rainwater and stormwater harvesting is shown to provide potable water savings of up to 39.0% of the annual average household potable water demand. Harvesting stormwater from the wetland also modifies the inundation frequency characteristics, which should lead to a significant improvement in the survival of vegetation throughout the wetland.