Feasibility of urban storm runoff as additional freshwater source : Singapore as a case study
Chen, Deh Chien
PublisherImperial College London
MetadataShow full item record
Freshwater is a finite resource. Faced with this challenge in the 21st century, there is an urgent need to augment existing sources of freshwater with sustainable alternatives. By adopting innovative demand management, water efficiency and conservation strategies, smart economics and advanced water technologies, water sustainability can be achieved as well as water security. The thesis posits that a decentralised system, like rooftop RWH, is feasible as an additional freshwater source running parallel to supplement and/ or complement the existing centralised mains water supply system for non-potable use even in high technology countries. Singapore, an urban city with abundant rainfall in a developed country context, is selected as a case study. As more than 80% of Singapore population lives in high-rise public housing, the HDB flats, rooftop RWH would augment the freshwater supply for urban storm runoffs that are discharged to the sea and are not collected in the stormwater collection ponds or reservoirs. Considerable potable water and cost savings would result as at least 25% of the potable mains water presently used for toilet-flushing, irrigation and floor-washing purposes could be substituted by rainwater. The centralised mains water supply system, as the main freshwater supply in socio-economic terms, is questioned as roofwater, with comparative good water quality, can be for non-potable use and thus supplement to meet the increasing water demand. RWH being a decentralised system, with numerous scattered water points throughout a city, has greater flexibility and autonomy and is less vulnerable to disruption in a distribution system, biological warfare and terrorism. For RWH to be successful, it must be carefully planned and designed to meet specific needs and conditions. In addition to enhancing technical guidelines, a combination of legislation, together with incentives, taxes and penalties helps to promote RWH and to maximize the benefits of implementing these systems. RWH is an under-used technology and strategy that can provide multiple benefits. When successfully implemented, RWH in the Singapore model can help close the gap in the total water cycle. It shows that even in a highly developed technological country like Singapore, there is room for a low but environmentally sound technology like RWH to play an important and relevant role. It is hoped that the lessons learned in Singapore can be replicated in other similar situations on a global scale.