Water is the primary source of living. We cannot imagine life without water, and it is the reality also that we are facing continuous threats of the shortage of water just because of misuse of water. In India, we have 17.7% of the world population but only 4% of the world fresh water resources. By 2025, it is predicted that large parts of India will join countries or regions having absolute water scarcity. Therefore, conservation of water is important for all of us. There are different ways of saving or conserving water, and rainwater harvesting is one of them.
Concept of Rainwater Harvesting
Rainwater is a free source of nearly pure water and rainwater harvesting refers to collection and storage of rainwater. Rainwater can be collected from rooftops and redirected to a deep pit or a reservoir. This water can be used for watering plants, washing and flushing. Thus, rainwater harvesting is a good example of water conservation. Rainwater harvesting is required due to several reasons which include
• To overcome the inadequacy of surface water to meet our demands.
• To increase groundwater levels at specific place and time and utilize rainwater for sustainable development.
• To increase infiltration of rainwater in the subsoil; this has decreased drastically in urban areas due to paving of open area.
• To improve groundwater quality by dilution.
• To reduce flood hazards and soil erosion.
• To improve ecology of the area by increase in vegetation cover etc.
Ancient Techniques of Water Conservation
Around the third century BCE, the farming communities in Baluchistan and Kutch (India) used rainwater harvesting for agriculture and many other uses. As per archaeological and historical records, Indians were adept in constructing dams, lakes and irrigation systems during the reign of Chandragupta Maurya. In the 11th century AD, the largest artificial lake in India was constructed by King Bhoja of Bhopal. It covered an area of over 65,000 hectares. Therefore, rainwater harvesting in India had been in practice from ancient times.
Rainwater Harvesting in India
Rainwater harvesting is common in areas having high rainfall intensity well distributed in the year. In India such areas include Himalayan region, North-Eastern states, Andaman and Nicobar islands, Lakshadweep islands, Rajasthan and the Southern parts of Kerala and Tamil Nadu.
Tamil Nadu was the first state to make rainwater harvesting compulsory for every building to avoid groundwater depletion. The scheme was launched in 2001 and has been implemented in all rural areas of Tamil Nadu. In ancient Tamil Nadu, rainwater harvesting was done by Chola kings. In Meghalaya, rooftop rainwater harvesting is the most common practice in Shillong. Nearly, every household in the city has a rooftop rainwater harvesting structure. Almost 15-25% of the total water requirement of the household comes from rooftop rainwater harvesting.
Bangalore had developed an intricate system of rainwater harvesting during 1860s itself. In Bangalore, adoption of rainwater harvesting is mandatory for every building having an area measuring 60 feet and above and for newly constructed building measuring 30 feet and above. Bangalore Water Supply and Sewerage Board has initiated and constructed ‘Rainwater Harvesting Theme Park in the name of Sir M Visvesvaraya in 1.2 acres of land situated at Jayanagar, Bangalore.
In Rajasthan, rooftop rainwater harvesting has traditionally been practiced by the people of the Thar Desert. Rainwater is captured from roof catchments and stored in reservoirs for future use. Rainwater from rooftops may be filtered and used for various purposes. Many ancient water harvesting systems in Rajasthan have now been revived. Water harvesting systems are widely used in all the areas of Rajasthan. Some of these are Tankas and Kundis for collection and use at the micro level and Talabs, Nadis, Tanks at the macro level; johads for recharge at the macro level. In the semi-arid and arid regions of Rajasthan, particularly in Bikaner, Phalodi and Barmer, almost all the houses traditionally had underground tanks or tankas for storing drinking water.
In Pune, rainwater harvesting is compulsory for any new housing society to be registered. In Mumbai, Maharashtra, rainwater harvesting is being considered a good solution to solve the water crisis. This practice of rainwater harvesting is not unique to India. It has been practiced worldwide in different forms.
Rainwater Harvesting in Other Countries
Rainwater harvesting is the normal practice for most rural housings in New Zealand. It is encouraged by most councils. Rainwater harvesting has been a popular method of obtaining water for agriculture and for drinking purposes in rural homes. The legislation to promote rainwater harvesting was enacted through the Urban Development Authority (Amendment) Act, in 2007. Water butts are often found in domestic gardens and on allotments to collect rainwater, which is then used to water the gardens.
In UK, the British Government’s code for sustainable homes encouraged fitting underground tanks to newly built homes to collect rainwater for flushing and washing. In Japan, a simple and unique rainwater utilization facility, Rojison, has been set up by local residents in the Mukojima district of Tokyo. They utilize rainwater collected froin the roofs of private houses for garden watering, fire-fighting and drinking water in emergencies.
New Approach to Rainwater Harvesting
A new approach to rainwater harvesting is developing a Rain Saucer. Instead of using the roof for catchment, the Rain Saucer collects rain straight from the sky. Rain Saucer looks like an upside-down umbrella. This decreases the potential for pollution in rainwater and makes potable water for developing countries a pollution ipprainwater and makes potable wat
Other innovative approaches for rainwater collection are sustainable gardening and small-plot farming. “Groasis Waterboxx’ is a Dutch invention which is very useful for growing trees in dry areas. The waterboxx is specially designed to collect dew and rainwater and slowly release it to keep the soil moist for plant growth. Recently, the National Green Tribunal (NGT) has directed all schools and colleges in Delhi to install rainwater harvesting system on their premises in two months. If the schools and colleges fail to do so, they will be liable to pay 5 lakh as a penalty.
Rainwater harvesting is the most sustainable and effective way to make water available in the areas lacking water. Rainwater harvesting is very low cost method and has lots of benefits. It helps in various purposes like household works, field irrigation, livestock, agriculture and animal husbandry.
Thus, harvesting through rainwater is not only saving the earth from becoming barren but also helping farmers to continue the cultivation process even under lesser rain and drought conditions.