Rain water harvesting is a technique of recharge of ground water by capturing and storing rain water. This is done by constructing special water-harvesting structures like dug wells, percolation, lagoon, check dams etc. Rain water harvesting is not only proving useful for poor and scantly rainfall regions but also for the rich ones. The annual average rainfall in India is 1,200 mm. It is astonishing fact that Cherrapunji (Assam), the place receiving the second highest rainfall is 11,000 mm still suffers from water scarcity. Rain water harvesting has the following objectives:
(i) To reduce run-off loss.
(ii) To avoid flooding of roads.
(iii) To meet the increasing demand of water.
(iv) To raise the water table by recharging ground water.
(v) To reduce ground water contamination.
(vi) To supplement ground water supplies during lean season. Rain water can be mainly harvested by any one of the following methods. (i) By storing in tanks or reservoirs above or below the ground. (ii) By constructing pits, dug-wells, lagoons, trench or check-dams on small rivulets. (iii) By recharging the ground water.
Traditional rain water harvesting:
In India it is an old practice in high rainfall areas to collect rain water from roof tops into storage tanks. Rajasthan is known for its underground tanks and khadins (embankments) for harvesting rain water. In our ancient times we had adequate Talaabs, baawaris, Johars, Hauz etc. in every city, village and capital cities of our kings and lords, which were used to collect rain water and ensured adequate water supply in dry periods. Modern techniques of rain water harvesting:
In arid and semi-arid regions artificial ground water recharging 'is done by constructing shallow percolation tanks. Check- dams made of any suitable native material (brush, poles, rocks, plants, loose rocks, wire nets, stones, slabs, sacks, etc.) are constructed for harvesting run-off from large catchments areas. Ground water flow can be intercepted by...
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