rXXXX American Chemical Society A dx.doi.org/10.1021/es103939a | Environ. Sci. Technol. XXXX, XXX, 000–000 ARTICLE pubs.acs.org/est Long-Term Trends and Opportunities for Managing Regional Water Supply and Wastewater Greenhouse Gas Emissions Murray R. Hall,* ,† Jim West, † Bradford Sherman, ‡ Joe Lane, § and David de Haas § † CSIRO Ecosystem Sciences, P.O. Box 2583, Brisbane Qld 4001, Australia ‡ CSIRO, Land and Water, Canberra ACT 2601, Australia § Advanced Water Management Centre, University of Queensland, Brisbane, Australia b S Supporting Information ’ INTRODUCTION The sustainability challenge for water supply and wastewater services in South East Queensland (SEQ) is framed by water shortages, a rapidly growing population, stressed aquatic ecosys- tems, and uncertain climate change. In turn, measures to provide water supply and wastewater services have implications for energy and greenhouse gas (GHG) emissions. In 2006, the region was suffering its worst drought in 100 years. Dam levels were very low and water restrictions were enforced to avoid completely depleting available reserves. In response, the regional Government developed a long-term water supply strategy to secure the future water supply. New water supplies proposed included desalination, recycled water, and rainwater tanks. These supplies aimed to give the water supply portfolio greater “climate independence” by reducing the reli- ance upon existing rain-fed water supply systems. However, many of the new water supplies also have considerably higher energy intensities than traditional surface water supply systems in the region. This study, funded through the Urban Water Security Re- search Alliance, aimed to inform long-term regional government planning strategies by identifying the largest contributors to energy and GHG emissions for urban water supply and waste- water services over the long-term. In particular, the relative contribution to GHG emissions was sought for: • centralized water supply and wastewater services; • decentralized water supply and wastewater systems; and • direct emissions from wastewater treatment and handling and urban water supply reservoirs. ’ EXPERIMENTAL SECTION Systems analysis with a long time frame was used to determine the relative significance as well as trends in GHG emissions from components of the urban water sector. The systems analysis also provided insight to management options to reduce GHG emis- sions. This approach was similar to other studies that consider entire system plans 1 but was different from other studies which focus on the performance of particular options 2À8 or aim to evaluate one option against another. 9À12 The study only con- sidered operational energy and GHG emissions, which was a limited system boundary compared to the full range of issues and stages of the life cycle. 13 Many other issues need to be considered to apply the study results to options evaluation. For example, freshwater extraction and wastewater disposal in the region have important implications for the receiving waters of Moreton Bay, which is an internationally significant wetland listed under the Ramsar Convention. 14 The South East Queensland Water Strategy (Strategy) is the regional government plan for providing urban water supply services to the region over the coming 50 years. 15 The Strategy was used to develop assumptions for population growth, long- term per capita water demand, preferred options, and the “level of service”. This research differed from the Strategy because it calculated a minimum energy curve by preferencing available Received: November 25, 2010 Accepted: April 11, 2011 Revised: April 6, 2011 ABSTRACT: Greenhouse gas emissions are likely to rise faster than growth in population and more than double for water supply and waste- water services over the next 50 years in South East Queensland (SEQ), Australia. New sources of water supply such as rainwater tanks, recycled water, and desalination currently have greater energy intensity than traditional sources. In addition, direct greenhouse gas emissions from reservoirs and wastewater treatment and handling have potentially the same magnitude as emissions from the use of energy. Centralized and decentralized water supply and wastewater systems are considered for a scenario based upon a government water supply strategy for the next 50 years. Many sources of data have large uncertainties which are estimated following the IPCC Good Practice Guidelines. Important sources of emissions with large uncertainties such as rainwater tanks and direct emissions were identified for further research and potential mitigation of greenhouse gas emissions.