A sufficient, safe drinking water supply is essential to life. However, millions of people throughout the world still do not have access to this basic necessity. After decades of work by governments and organisations to bring potable water to the poorer people of the world, the situation is still dire. The reasons are many and varied, but generally speaking, the poor of the world cannot afford the capital intensive and technically complex traditional water supply systems. Unfortunately these technologies are widely promoted by governments and agencies throughout the world. Rainwater harvesting (RWH) is an alternative to these unaffordable options. It has been adopted in many areas of the world where conventional water supply systems have not been provided, too expensive or failed to meet people’s needs. RWH is a proven technology that has been in use since ancient times.
Examples of RWH systems can be found throughout history. In industrialised countries, sophisticated RWH systems have been developed to reduce water bills or to meet the needs of remote communities or individual households in arid regions. RWH is also used in developing countries. In Uganda and Sri Lanka, for example, rainwater is traditionally collected from trees, using banana leaves or stems as temporary gutters. Up to 200 litres may be collected in this way from a large tree in a single storm. Many individuals and groups have taken the initiative and developed a wide variety of RWH systems throughout the world.
Many kinds of rainwater harvesting are practised throughout the world. Basically RWH may be divided into two types:
- Domestic RWH
- RWH for agriculture, erosion control, flood control and aquifer replenishment
Domestic RWH is a simple mechanism to collect and store rainwater mainly for drinking and cooking. It may be household based or community based. The system uses a collection surface such as a roof, gutters to guide the rainwater, and a container to store the water.
Larger RWH systems are used for water resource management. These systems use vast catchment areas to collect rainwater and store it in reservoirs. The water is then used for irrigation or to recharge aquifers. These systems may also help in flood control and erosion prevention by holding storm water into reservoirs and discharging at a controlled rate.
This paper involves domestic RWH only. We must remember that rainwater harvesting is not the ultimate answer to household water problems. Many factors have to be considered when selecting the appropriate water source. These include cost, climate, hydrology, social and political elements, as well as technology. All of these play a role in making the final choice of a suitable water supply scheme. RWH is only one of many possible choices. But RWH is often overlooked by planners, engineers and builder.
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