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< prev - next > Water and sanitation Rainwater harvesting KnO 100022_Rainwater harvesting (Printable PDF)
Rainwater Harvesting
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 builders.
The reason that RWH is rarely considered is often due to barriers such as lack of technical
and other information. In many areas where RWH has been introduced as a part of drinking
water supply options, it was at first un-popular. This was simply because little was known
about the technology by the beneficiaries. In most of these cases, the technology has quickly
gained popularity. The users soon realised the benefits of a clean, reliable water source at the
home. This is especially true in areas where the town supply is unreliable or where local water
sources dry up for a part of the year. In many cases RWH has also been introduced as a part
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