What is Rain Water Harvesting?
Rain water harvesting (RWH) is catching rain water when it falls and storing to use during the non rainy season. Harvested rain water can be utilized for several purposes including drinking, washing, gardening, flushing etc. This is practised throughout the world and it is increasing in demand. In Sri Lanka, we have been practising it throughout the history by collecting water in Wewa or tanks. However concept of rain water harvesting in houses and offices etc. is relatively new to us and according to statistics available, more than 21,000 rain water harvesting systems are in operation throughout the country, mostly in rural areas.
RWH in Rural Areas
Specially in areas which are vulnerable to periodic droughts, RWH is a viable option for the basic water needs.
This water can be used for domestic use including drinking, cooking, washing and also for the needs of agriculture. Closed tanks made of brick or cement which collect water from the roof top are used to harvest water for domestic use. Open tanks or wells can be used to collect the surface runoff water which can be used for agriculture and also for ground water recharging.
RWH in Urban Areas
RWH in Urban areas is increasingly becoming popular with appropriate technology. According to studies about 60 percent of rainwater of urban areas flow in to sea and RWH can make use of this wasted water and also to certify the use of purified pipe borne water for appropriate usages. Tanks can be used to collect water for general use and wells and pit holes (surface runoff tanks) can be used to recharge the ground water. Ponds are used in large facilities such as factories and office complexes for collection of rain water.
The water collected in tanks and ponds can be used for toilet flushing, washing, cleaning, laundry, and gardening. However, rainwater collected in urban areas is not recommended for drinking and cooking due to the high level of air pollution, animal droppings and dust in urban areas.