Rainwater Harvesting
Today's Rainwater, Tomorrow's Drinking Water
Rain water is the gift of God for use of all. It is one of the basic needs for survival. In villages there are deep wells, shallow wells and ponds that clearly point to the high priority the ancients gave for water conservation. With large scale and haphazard urbanization, the values of simple and effective traditional techniques of water conservation were ignored. Now the people have realized these values and are taking steps to revive the old and trusted techniques.
For centuries rivers and tanks met the drinking water and irrigation needs of the people. In those days people living far away from the river course and wetlands conserved rainwater in large walls and regulated the rainwater to fall into ponds and lakes. During the summer months they utilized the stored rainwater for drinking and irrigating thousands of acres of agricultural land. The community controlled the water use.
Rainwater does go waste if it is not properly regulated. Cheerapunji in Assam receives almost 12,000 mm of rainfall per annum, yet people there face drinking water scarcity while in arid Rajasthan it hardly rains for a month. However, the industrious villagers store rainwater in large natural and man made reservoirs by adopting rainwater-harvesting techniques for use during the months of scarcity.
Tanks and ponds that adorn the villages are now shrinking in numbers. Many water bodies are facing the threat of extinction. Natural reservoirs have slowly been fading away due to encroachment, land grabbing, and poor planning.
In urban areas, concrete buildings and asphalted roads prevent water from seeping into the ground. When it rains the rainwater just gushes out into the drains. Because of this the ground water is not replenished and the water table does not rise.
The need for conserving rainwater is now more vital than ever before. In these days of water scarcity the traditional techniques must be revived for saving precious water. Rainwater Harvesting (RWH) is the technique of collecting and storing rainwater wherever it rains instead of allowing it to go waste. Rainwater recharge is a method to increase rainwater infiltration in the soil surface to raise the ground water table.
How to conserve rainwater? Collecting water from the rooftops through pipes and discharging into we11s, recharging of defunct bore wells and open wells through percolating pits, regulating it to flow into ponds and lakes are some of the efficient and cost effective methods to augment water supply.
The cost of making percolating pits around a 100 sq m house with filter tank and underground pipe leading to the well works out to approximately·Rs.6000/-. For a 20 m x 30 m multistoried building the cost of making 1 m x I .5 m deep percolating pits around it with drain pipes, filter tank and underground piping to the well will be around Rs.75, 000/-.
For row houses and business complexes it works out to approximately Rs.2, 00,000 and Rs.90, 000 respectively.
An independent house in Bangalore can on an average save about 40,000 liters of rainwater per year after meeting all the needs. Rainwater conservation augments ground water level; raises water level in the existing wells; re- charges defunct bore wells and open wells; prevents cracking of building walls due to presence of moisture in the soil; decreases the salinity of soil and increases the quality of ground water and the moisture content of the soil; increases soil fertility due to growth of vegetation; stops seepage of seawater into the ground water; stops soil erosion Conserving rainwater not only solves the drinking water problems the people face during the summer months, but also irrigates several acres of agricultural land in draught affected areas.
While granting license to construct new buildings the authorities must ensure that the building plan has provision for rainwater harvesting. If it is not provided, then the authorities shall not grant license to the builders.
This is not sufficient. Government's propaganda machinery must galvanize in to action to popularize this inexpensive and very efficient technique of water saving concept.
This is not sufficient. Government's propaganda machinery must galvanize in to action to popularize this inexpensive and very efficient technique of water saving concept.
Lakes must be de- silted and deepened to hold more water, In villages too this concept must be popularized. The World Bank has warned of severe drinking water scarcity in India in the year 2025. Scanty rainfall in the recent years is perhaps indicating the shape of things to come. It is high time government acted with all seriousness to ward off the impending disaster. Having a green belt without any water scarcity is known as a blue belt area, that is when we recharge the ground water and change the conditions of a place from one of scarcity of water to one of sustenance. This can be achieved through RWH techniques and this will save Bangalore from water scarcity. Bangalore's topography is particularly suitable for rainwater harvesting.
The and the granite rock underneath are well suited for RWH. These are unique qualities and it should be tapped to the maximum. Also Bangalore gets about 850 mm rainfalls annually. This gift from Mother Nature shall not go down the drain.
Though about 700 million liters of water from Cauvery and other sources are being generated daily, yet there is a wide gap between supply and demand. At current rate of consumption, the city needs additional 150 million liters daily. In a few years from now water supply as high as 2200 million liters daily would be needed. RWH is a less expensive affair. Anyone can adopt this technique.
Government buildings, large educational institutions, hospitals, satellite ownships, condominiums and independent households must adopt this technique. In so doing, water scarcity during the summer months can be contained to a great extent. Reports say that government is preparing action plans in all districts to tackle the problem of drinking water shortage on account of failure of monsoons. There are about 56,000 villages and hamlets in the state, which face drinking water crisis one time or the other. The problem accentuates when there is scanty rainfall.
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