Domestic water supply using rainwater harvesting

World-wide pressure on water resources is mounting as populations grow, consumption per capita increases, 'fossil' water resources are mined and the climate changes. Domestic water usage is a significant component of water demand. Under favourable circumstances, it can be met in part or in whole by rainwater collected close to an individual dwelling. Interest in such systems is growing especially in rural areas where either rainfall is well distributed through the year, or where surface water is absent, groundwater mineralized and centralized piped supplies unaffordable. Roofwater collection is also being practised on low-rise and high-rise buildings in some cities having wet climates. The principles and components of rainwater harvesting are reviewed. Factors leading to the growing use of domestic rainwater harvesting in three different developing countries (North China, East Africa and Singapore) as case studies are discussed along with current practices, design options for system components and considerations for water quality and treatment. The lessons from developing countries can be applied to a European context as some European towns are beginning to require rainwater collection for toilet/laundry facilities in some new buildings.