Water harvesting is another way in which we can manage our water needs properly. Since ancient times, many communities have used hundreds of indigenous water saving methods to capture every trickle of water that had fallen on their land; dug small pits and lakes, put in place simple watershed systems, built small earthen dams, constructed dykes, sand and limestone reservoirs, set up rooftop water-collecting units. This has recharged groundwater levels and even brought rivers back to life.
In largely level terrain, the water harvesting structures are mainly straight concrete-and rubble “check dams” built across seasonally flooded gullies. Monsoon rains fill ponds behind the structures. These structures then recharge the ground-water beneath.
Water harvesting is an age-old concept in India. Khadins, tanks and nadis in Rajasthan, bandharas and tals in Maharashtra, bundhis in Madhya Pradesh and Uttar Pradesh, ahars and pynes in Bihar, kulhs in Himachal Pradesh, ponds in the Kandi belt of Jammu region, and eris (tanks) in Tamil Nadu, surangams in Kerala, and kattas in Karnataka are some of the ancient water harvesting, including water conveyance, structures still in use today (see Fig. 16.4 for an example). Water harvesting techniques are highly locale specific and the benefits are also localised. Giving people control over their local water resources ensures that mismanagement and over-exploitation of these resources is reduced/removed.
In largely level terrain, the water harvesting structures are mainly crescent shaped earthen embankments or low, straight concrete-andrubble “check dams” built across seasonally flooded gullies. Monsoon rains fill ponds behind the structures. Only the largest structures hold water year round; most dry up six months or less after the monsoons. Their main purpose, however, is not to hold surface water but to recharge the ground water beneath.
Advantages of storing water in ground
The advantages of water stored in the ground are:
-It does not evaporate, but spreads out to recharge wells and provides moisture for vegetation over a wide area.
-It does not provide breeding grounds for mosquitoes like stagnant water collected in ponds or artificial lakes.
-The ground-water is also protected from contamination by human and animal waste.