Drought proofing cities: Desalination versus rainwater tanks – a challenge to water supply managers

Abstract Drought is affecting water supply in many cities across Australia. However, rainwater tanks do not appear to be considered a serious water supply option by many government agencies. The major concern about rainwater tanks for drought response is the yield they would provide during drought conditions. The results presented in this paper challenge the widely held assumption that rainwater tanks cannot provide a reliable supply during drought. Rainwater tank modelling undertaken during a severe drought from 1998 to 2006 in the water supply catchment showed that rainwater tanks on single dwellings increase water supply storage levels by at least 15%, raising storages from less than 40% to above 60%. Rainwater tanks can also provide similar securities of supply as a desalination scheme that was run as a drought relief measure and not as a constant base load. Furthermore, the real cost per kilolitre of desalination is challenged by investigating the assumption that once a desalination plant is built, it will be running constantly. However, cost, climate change and energy management suggest that the desalination plant be used only when required. Depending on the operating model of the desalination plant, the levelised cost can vary from $1.55 to $6.80 /kL. This compares with rainwater tanks, which have a levelised cost of $2.20 to $4.20 /kL.