Using treated wastewater to save wetlands impacted by climate change and pumping

摘要

Wetlands occur where the watertable which underlies much of Perth intersects the land surface. Regional groundwater levels have been falling since the 1970s as a result of lower rainfall and increased extraction causing a loss of environmental and social values. This paper examines a scheme to add almost 2 GL/yr of treated wastewater to infiltration galleries immediately down-gradient of Perry Lakes so that the wetlands may be restored. Modelling suggest that groundwater levels would be raised up-gradient of the galleries, increasing both lake levels and groundwater supplies in the vicinity. It is not envisaged that wastewater will enter the lakes. Adding treated wastewater to nearby trial galleries has shown that phosphorus, pathogens and organic carbon are greatly reduced within 5 to 50m. Nitrogen levels are less reduced but are similar to those in the lakes and nearby aquifer. It is estimated that the wetlands add about