Water Resources
Rainwater harvesting
Describe old and new ways of harvesting rainwater.
Old wisdom: catch the rain where it falls. People knew their rain and their soil, and built to suit them:
- hills: 'guls' or 'kuls' of the Western Himalayas, channels that carry stream water to the fields;
- Rajasthan: rooftop rainwater harvesting for drinking water;
- flood plains of Bengal: inundation channels to water the fields;
- dry areas: fields that hold rain so it stands and soaks the soil, like the khadins of Jaisalmer and the johads elsewhere in Rajasthan.
The tanka. In Bikaner, Phalodi and Barmer, almost every house had a tanka: an underground tank, sometimes as big as a room, inside the house or courtyard.
- Rain falls on the sloping roof.
- A pipe carries it down into the tanka.
- The first rain is not kept, because it washes the dirt off the roof and pipes. Later showers are stored.
This water, called palar pani, is thought of as the purest natural water, and it lasts till the next rains. Some houses built cool underground rooms beside the tanka to escape the summer heat.
Tankas fading out. In western Rajasthan, fewer people keep tankas today because the Indira Gandhi Canal brings water all year. Some still do, because they prefer the taste of tanka water to tap water.
Rooftop harvesting today (Fig. 3.3). Rain from the roof goes down a PVC pipe and is filtered through sand and bricks. It flows to a sump for use now, and the extra goes into a well, through a hand pump or an old, unused dug-well, to recharge the groundwater. Think of it this way: if a pipe can pull water up from the ground, it can also send rain back down.
Tamil Nadu was the first state to make rooftop rainwater harvesting compulsory for every house, with punishment for those who don't.
Two success stories.
- Gendathur (Mysuru, Karnataka): about 200 households harvest rain from their roofs. Each house can collect about 50,000 litres a year, and the village is now known as rich in rainwater.
- Shillong (Meghalaya): Cherrapunjee and Mawsynram, only 55 km away, get the heaviest rainfall in the world, yet Shillong is short of water. Nearly every house has rooftop harvesting, which meets about 15-25 per cent of its needs.
Bamboo drip irrigation (Meghalaya). A 200-year-old system. Bamboo pipes carry water from springs on the hilltops down the slopes by gravity, over hundreds of metres. About 18-20 litres go in at the top; at the end only 20-80 drops a minute fall right at the roots of the plant. Nothing is wasted.
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