ABSTRACT
Water is a vital source for the very existence of human beings on Earth. Although the total volume of water on Earth has remained constant since its creation, its variation over space and time, with respect to quantity and quality, presents some unique
problems and challenges to all who have an interest in water. e major source of water is the ocean; however, this water cannot be consumed directly due to poor quality. Water in lakes and rivers oen needs treatment before it can be consumed by human beings. Only groundwater, rainwater in some areas, and some spring water may be consumed without treatment. In urban
60.1 Introduction ............................................................................................................................ 805 60.2 Rainwater Harvesting Systems in Urban Areas ................................................................. 806 60.3 Rainwater Harvesting System versus Onsite Detention ................................................... 807 60.4 Water Savings from Rainwater Harvesting Systems ......................................................... 808 60.5 Essential Components of a Rainwater Harvesting System .............................................. 808
Roof Catchment • Types of Tanks • Accessories of a Rainwater Harvesting System 60.6 Quality of Water from a Rainwater Tank ........................................................................... 809 60.7 Sizing of a Rainwater Tank ..................................................................................................... 810 60.8 Maintenance of a Rainwater Harvesting System ................................................................ 811 60.9 Economics of Rainwater Harvesting Systems ..................................................................... 812 60.10 Summary and Conclusions .................................................................................................... 812 References ............................................................................................................................................. 812
Preface A rainwater harvesting system (RWHS) is the most popular alternative water supply system in many cities around the world. It has been found that a typical RWHS in an urban area can save 20%–60% of mains water depending on the local rainfall, roof size, number of occupants in the house, and types of water use. To estimate an appropriate size of a rainwater tank for a given application, a rainwater tank model should ideally be adopted, which considers local rainfall, roof area, and water demand data to determine an appropriate tank size. However, for general purposes, standard local council guidelines may be used to select an appropriate tank size. For example, in Sydney, Australia, for a detached house with 4 people, if rainwater is to be used for toilet ushing, washing clothes, and moderate gardening, a 5-kL tank may be adopted. In general, water from an RWHS can safely be used for nonpotable purposes. However, it is not recommended to drink water from an RWHS without treatment, in particular for people who fall in immuno-compromised groups (e.g., children, old people, and cancer patients). A RWHS must be maintained regularly if the water is to be consumed by human beings.
