Rain Water Harvesting

Rainwater Harvesting: Rainwater harvesting is the accumulation and storage of rainwater for reuse before it runs-off. Uses include water for the garden, water for livestock, water for irrigation etc. Due to increasing problems resulting from multi-purpose river projects, water harvesting systems are an alternative for improvement in water availability. It does not harm the environment also.

In India, there existed an extraordinary tradition of water harvesting system keeping in mind the climatic conditions and water needs. People had knowledge of rainfall systems and techniques to harvest groundwater, rainwater, river water and flood water.

Rainwater Harvesting Methods in India

1. Khadins and Johads: In arid and semi-arid regions, agricultural fields were converted into rainfed storage structures that allowed the water to stand and moisten the soil like the Khadins in Jaisalmer and Johads in other parts of Rajasthan.

2. Rooftop rainwater harvesting: People living regions of Rajasthan and Gujarat, where rainfall is scanty, have used rooftop rainwater harvesting systems to store drinking water. Process of rooftop rainwater harvesting is given below

NOTE : Rainwater Harvesting in Shillong: It is the most common practice in Shillong, Meghalaya. It is interesting because Cherapunjee and Mawsynram situated at a distance of 55 km from Shillong and receive the highest rainfall in the world, yet the State Capital Shillong faces acute shortage of water. Nearly every household in the city has a rooftop rainwater harvesting structure. Nearly 15-25 per cent of the total water requirement of the household comes from rooftop water harvesting. Rainwater that falls on the sloping roofs of houses is taken through a pipe into an underground tanka ( Circular Hole in The Ground )

3. Tankas or Tanks. The Tanks in Semi-arid and arid regions of Rajasthan, particularly in Bikaner, Phalodi and Barmer can store rain water that is locally called Palar Pani. Here they have used underground tanks (called tankas) for water storage. The process is similar to rooftop rainwater harvesting system. The tanks could be as large as a big room; one household in Phalodi had a tank that was 6.1 metres deep, 4.27 metres long and 2.44 metres wide

4. Inundation channels: In the flood plains of Bengal, people developed inundation channels (is a channel that is connected to a large river so that the flood water in the river flows in it) to irrigate their fields.

5. Guls or Kuls: In hilly and mountain regions, people built diversion channels to collect rainwater, spring water and store in circular tanks like the ‘guls’ or ‘kuls’. For example, Western Himalayan i.e. Himachal Pradesh for agriculture.

6. Bamboo drip irrigation system: This system for irrigation is in use for 200 years in Meghalaya. It is old system of utilising stream and spring water by using bamboo pipes. Spring water from the hill slopes, flows into the bamboo pipes which is then transported to distant places through the same pipes.

Advantages of Rainwater Harvesting :

Now-a-days, perennial Rajasthan canal supplies plenty of water in the Western Rajasthan and consequently the practice of rooftop rainwater harvesting is declining. In many parts of rural and urban India, rainwater harvesting successfully adapted to store and conserve rainwater. One such example is a remote village in Mysore, Karnataka named Gendathur that has installed about 200 rooftop rain harvesting systems. Gendathur receives an annual precipitation of 1000 mm and with 80 per cent of collection efficiency and of about 10 fillings; every house can collect and use about 50000 litres of water annually. From the 20 houses, the net amount of rainwater harvested annually amounts to 100000 litres.

Note: Tamil Nadu is the first and the only state in India which has made rooftop rainwater harvesting structure compulsory to all the houses across the state and punish the defaulters.