Rainwater harvesting: Oldest method of storing rainwater
RAINWATER HARVESTING in rural Karnataka was initiated by the Karnataka state for Science and Technology, which is one of the largest rainwater harvesting projects in the world. One of the reasons for an initiative like this is the shortage of drinking water, which is such that Karnataka sometimes has opted for alternatives like, cloud seeding to bring rain artificially.
The Bangalore Water Supply and Sewage Board (BWSSB) currently supplies 900 million litres of water to the city per day where as the demand for water is of 1.3 billion litres. The Cauvery River is the main source of water for the Bangalore city, which is imported by the BWSSB.
Rainwater harvesting technology drew closer in meeting the solution of acute water shortage in Bangalore. The rainwater club started in the year 1995, which incorporated of architects and engineers who were inclined on integrating rainwater harvesters into buildings.
In the next few months every building in Bangalore would be equipped with rainwater harvesters as per the provisions of the Karnataka Ground Water Regulation and Control of Development and Management Bill 2007. Also the BWSSB has made it mandatory for applicants of water connections to install rainwater harvesters.
Rainwater harvesting is used for storing of water for domestic, livestock and irrigation, which also lessens urban flooding and improves the quality of groundwater increasing the groundwater table through artificial recharge, which is a process where the ground water reservoir is augmented by refilling.
There are two main techniques of rainwater harvestings that include; storage of rainwater on surface for future use and recharge to ground water. Storing water on surface is one of the traditional techniques and structured by tanks, ponds and check dams. Recharge to ground water is a new technique, which composes of: pits, trenches, dug wells, hand pumps, recharge wells, and recharge shafts, lateral shafts with bore wells and spreading techniques.
Awareness of rainwater harvesting is much talked about rather than being implemented comment most of the architects in Bangalore.
"The urban population has lost their connection to their roots," says Jeeth Iype, architect, Good Earth Homes.
He also added that people construct buildings and houses and cover most of the ground leaving no space for rainwater to settle down.
Jeeth also stated that media should play its role in creating awareness of how important is setting up rainwater harvesters while constructing houses and buildings.
’Good Earth Enclave’ that is situated at Uttarahalli near Kengeri is the best example of environment friendly homes. Jeeth Iype is one of the residents here, who says that there is no need for rainwater harvesters since this colony has lot of space for absorbing rainwater. The colony also has a well, a pond and array of plants and trees surrounding the homes that are built of bricks and not cement blocks.
The residents of Beedi Colony have been storing rainwater since two years. Nazima, a resident says that all the houses use the rainwater for washing utensils, clothes and bathing.
Beedi workers housing scheme includes rainwater-harvesting technology, which is funded by Indo Norwegian environment programme an implemented by Karnataka State Council for Science and Technology. The process includes filtration of rainwater from the building roof and stored in a surface tank of 7,500 litres at each site. The annual potential of the rainwater harvesting here is 4,38,000 litres of water.
"Spend a little today for a better tomorrow," says Vimal Jain, architect, Paradigm.
He also said that it is the responsibility of an architect to make the clients understand how important utilising rainwater for at least domestic use is.
Vimal also stated, "Government should reinforce the law that exists, there are many laws as such but how many are implemented, that is why there should be ’shrewd penalties’ charged."
When should one store rainwater and when one should use it for recharge?
This depends on the rainfall pattern and the region. In Delhi, Rajasthan and Gujarat where rainfall occurs during three to four months, here groundwater recharge is usually practised, where as in Kerala, Bangalore and Tamil Nadu where rain falls throughout the year one can depend on storing rainwater.
Why is rainwater harvesting important?
Surface water is inadequate to meet the demand for water another reason is rapid urbanisation.
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This can be seen in Bangalore, where most of the rural areas do store rainwater but the urban population is so much involved in buildings that can attract the customers and houses, unlike some of the colonies that are environment friendly fails to realise that environment should not be taken lightly.
Till about thirty years back the areas around homes and offices used to be unpaved and the rainfall would percolate into the soil, but due to the proliferation of flats and complexes the percolation of water has suddenly come to a stop. Most of the architects in Bangalore blame the government for not implementing the law and also there is less awareness among the people of how important is rainwater harvesting.
Added to that comes another misconception that rainwater harvesting is a new technique, which is absolutely false.
In India, it was in 4500 BC when the water was harvested for earthworks in the Thar Desert and Rajasthan, whereas in the Palestine and Greece it existed 4000 years ago.