Abstract
Problem statement: The urban water supply systems in Australian large cities, which generally depend on large surface water reservoirs, are highly stressed due to rapid urban growth and severe drought conditions during the current decade . To ensure the long term sustainability of urban water supply, various alternative water sources inc luding rainwater tanks, grey water, wastewater and desalination plants are being examined in Australia . In the previous research, it has been shown that rainwater tank of appropriate size, installed in de tached small dwellings, can meet a significant proportion of household water demand, but there has been limited study on water savings and financial viability of Rain Water Harvesting System (RWHS) for multistorey residential buildings. This study examines the sustainability of RWHS in multistorey residential buildings in Sydney under different scenarios such as varying roof area, number of floo rs in the building, water price and interest rate t o identify favorable condition where RWHS proves to be sustainable. Approach: A hypothetical multistorey building was considered and various sce narios in relation to site area and floor arrangement were established. A water balance model was developed to calculate water savings for various scenarios. Finally, life cycle costing was undertaken to identify most sustainable RWHS scenario for the hypothetical multistorey building. Results: It was found that a higher roof area is more favorable in terms of water savings and financial b enefits. Capital and maintenance costs account for the majority of the expenditure of a RWHS. Plumbing cost forms the largest single component of the capital cost. It is shown that lower interest and i ncreased water price regimes enhance the financial viability of RWHS. Conclusion: It was found that it is possible to achieve pay b ack for a RWHS under some favorable scenarios and conditions thus making the RWHS for multistorey buildings in Sydney sustainable.
Highlights
Australia is a highly urbanized country and perhaps the driest inhabited continent on earth with highly variable rainfall
A rainwater tank of appropriate size can meet a significant proportion of household water demand for small dwellings and quality of water from the tank is not a problem for non-potable uses, the financial viability of a rainwater harvesting system (RWHS) to individual house owner is yet to be established, in particular with the current water price in Australia
The results obtained from this study showed that the use of rainwater tanks resulted in considerable mains water savings in each city
Summary
Australia is a highly urbanized country and perhaps the driest inhabited continent on earth with highly variable rainfall. For the last 10 years and so, Australia has been experiencing severe drought which has created significant water management problems. Three major cities in Australia namely Sydney, Melbourne and Brisbane where about 50% of Australia’s total population live have been experiencing mandatory water restrictions for the last 5 years and so. Water supply authorities in Australia has been desperately looking for alternative sources of fresh water including rainwater tanks in addition to recycling grey water, wastewater and use of desalination plants. A rainwater tank of appropriate size can meet a significant proportion of household water demand for small dwellings and quality of water from the tank is not a problem for non-potable uses, the financial viability of a rainwater harvesting system (RWHS) to individual house owner is yet to be established, in particular with the current water price in Australia. There is a general lack of research on long term sustainability of rainwater tanks, in particular for multistorey residential developments
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