Rainwater Harvesting is a process involving collection and storage of rain water (with the help of artificially designed system) that runs off natural or man-made catchment areas e.g. roof top, compounds, rock surface or hill slopes or artificially repaired impervious/semi-pervious land surface
Importance of implementing rain-water harvesting:
a) To reduce Runoff loss: More than 3/4th of the precipitation In India comes during 4 months (monsoon). A significant part of which is lost in runoff and evaporation, this can be controlled by rain water harvesting.
b) To meet Rising demand: Rapid urbanization and Industrial development demands huge water hence severe water crunch can be solved by water harvesting.
c) For Agriculture & food security: Modern hybrid crops & fertilizer depend on continuous supply of irrigation water. More than 60% of net sown area is unirrigated (rising cases of drought in the dry belt of India)
d) Women issues: In dry and hilly areas women face hardship in fetching water. Rain water harvesting can provide a decentralized source of water.
i. The cost of recharge to sub-surface reservoir is lower than surface reservoirs.
ii. The aquifer serves as a distribution system also.
iii. No land is wasted for storage purpose and no population displacement is involved.
iv. Ground water is not directly exposed to evaporation and pollution.
v. Storing water under ground is environment friendly.
vi. It increases the productivity of aquifer.
vii. It reduces flood hazards.
viii. Effects rise in ground water levels.
ix. Mitigates effects of drought.
x. Reduces soil erosion.
Rain Water Harvesting Techniques:
There are two main techniques of rain water harvesting.
1. Storage of rainwater on surface for future use.
2. Recharge to ground water.
Roof top rain water/storm runoff harvesting through:
(i) Recharge Pit
(ii) Recharge Trench
(iv) Recharge Well
Rain water harvesting through:
(i) Gully Plug
(ii) Contour Bund
(iv) Percolation Tank
(v) Check Dam/Cement Plug/Nala Bund
(vi) Recharge Shaft
Examples of Traditional water harvesting system in India
◦ Trans-Himalayan Region
▪ Zing -Tanks for collecting water from melted ice in Ladakh.
◦ Western Himalayas
▪ Kul -Water channels in mountain areas Jammu, Himachal Pradesh.
▪ Naula -Small ponds in Uttaranchal.
◦ Eastern Himalayas
▪ Apatani -Terraced plots connected by inlet and outlet channels in Arunachal Pradesh.
◦ Northeastern Hill Ranges
▪ Zabo -Impounding runoff in Nagaland
▪ Bamboo drip irrigation - Water from streams in the hills is brought to the plains via bamboo pipes for drip irrigation in Meghalaya
◦ Brahmaputra Valley
▪ Dongs –Ponds in Assam
◦ Indo-Gangetic Plain
▪ Dighis -Small square or circular reservoir fed by canals from rivers in Delhi
◦ Thar Desert
▪ Baoris / bers -Community wells in Rajasthan
▪ Tankas -Underground tank Bikaner in Rajasthan
◦ Central Highlands
▪ Johads -Earthen check dams in Alwar district, Rajasthan
Rain water harvesting not only provides the most sustainable and efficient way of water management but also opens the vista of several other economic activities leading to Empowerment of people at grass root. For this Government should come out with appropriate incentive structure and logistics support to make it a real success.