Oral Presentation Australian Society for Limnology Congress 2013

Extreme events and the increasing risk of contamination of urban waterways and wetlands (#18)

Jenny A Davis 1 , Ian M Kidd
  1. Monash University, CLAYTON, VIC, Australia

Launceston, in northern Tasmania, is Australia’s third oldest city and supports a regional population of 90,000. Residents have long been concerned about poor water quality and excessive sedimentation in the Tamar River, on the cities doorstep.  Silt raking is currently being used as a short term solution and has unexpectedly exposed massive sewage contamination. Specifically, the silt rake has often become clogged with tampon strings. The cause can be attributed to aging urban infrastructure.  The sewage and stormwater runoff from older parts of the city are combined. This means that the secondary treatment plants cannot cope with the sudden increase in stormwater that occurs during high rainfall events. At these times all wastewater (stormwater and raw sewerage) is released directly into the Tamar River. The problem of sewage overflows into natural waterways and wetlands occurs throughout Australia. Pumping stations are often located close to streams or wetlands which are intended to act as emergency receiving waters when pumps fail or systems become overloaded. The Launceston issue is a timely warning. We have to ensure that urban wastewater infrastructure is designed to cope with extreme events. We need to acknowledge the adverse water quality outcomes likely to arise from organic pollution under a warming climate. If not, the important biodiversity, recreational and aesthetic values of urban wetlands and waterways will disappear and the risk of water-borne and mosquito-borne diseases will increase.