Rainwater harvesting is very old technique of water conservation in many parts of the world. We can find examples of rainwater harvesting systems in the history of great civilizations. As the name itself suggests, it involves collecting the rainwater and storing it. The technology can be as simple or as complex as required. The collected rainwater can be stored in metal or plastic tanks, which can be used for domestic or industrial purposes or it can be used to recharge the ground water.
Excessive tapping of ground water through numerous tube wells has led to a fall in water table in many parts of our country. To avoid the alarming fall of ground water table, the aquifer must be recharged by collecting every drop of rainwater,since that is the only source of ground water.
In India, traditionally we used to store the rainwater in ponds, which were used as surface water sources for drinking, irrigation and other purposes. However loss of water by evaporation is more in these. With increasing population, there is growing\ need of land for housing. These ponds are fast disappearing even in small towns due to this growing need of land for housing. This is leading to change in thinking.Now we have two options for better use of rainwater. In first option, the rainwater can be harvested and stored in a storage tank for latter use. The second option involves recharging the ground water with harvested rainwater. Various recharge structures are available to recharge the rainwater into ground. These are outlined here:
Pits : Recharge pits are constructed for recharging the shallow aquifer. These are constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders,gravels and coarse sand.
Trenches: These are constructed when the permeable stream is available at shallow depth. Trench may be 0.5 to 1 m. wide, 1 to 1.5m. deep and 10 to 20 m.long depending up availability of water. These are back filled with filter materials.
Dug wells: Existing dug wells may be utilized as recharge structure and water should pass through a graded filter or other filter media before putting into dug well.
Hand pumps: The existing hand pumps may be used for recharging the shallow/deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.
Recharge wells: Recharge wells of 10 to 30 cm diameter are generally constructed for recharging the deeper aquifers and water is passed through filter media to avoid choking of recharge wells.
Recharge Shafts: For recharging the shallow aquifer which is located below clayey surface, recharge shafts are used. The size of recharge shaft is 0.5 to 3 m diameter and 10 to 15 m deep. After digging, these are back filled with boulders,gravels and coarse sand.
Spreading techniques: When permeable strata starts from top then this techniqueis used. Spread the water in streams/canals by making check dams and bunds. A percolation pond may be constructed in low-lying areas.
Excessive tapping of ground water through numerous tube wells has led to a fall in water table in many parts of our country. To avoid the alarming fall of ground water table, the aquifer must be recharged by collecting every drop of rainwater,since that is the only source of ground water.
In India, traditionally we used to store the rainwater in ponds, which were used as surface water sources for drinking, irrigation and other purposes. However loss of water by evaporation is more in these. With increasing population, there is growing\ need of land for housing. These ponds are fast disappearing even in small towns due to this growing need of land for housing. This is leading to change in thinking.Now we have two options for better use of rainwater. In first option, the rainwater can be harvested and stored in a storage tank for latter use. The second option involves recharging the ground water with harvested rainwater. Various recharge structures are available to recharge the rainwater into ground. These are outlined here:
Pits : Recharge pits are constructed for recharging the shallow aquifer. These are constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders,gravels and coarse sand.
Trenches: These are constructed when the permeable stream is available at shallow depth. Trench may be 0.5 to 1 m. wide, 1 to 1.5m. deep and 10 to 20 m.long depending up availability of water. These are back filled with filter materials.
Dug wells: Existing dug wells may be utilized as recharge structure and water should pass through a graded filter or other filter media before putting into dug well.
Hand pumps: The existing hand pumps may be used for recharging the shallow/deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.
Recharge wells: Recharge wells of 10 to 30 cm diameter are generally constructed for recharging the deeper aquifers and water is passed through filter media to avoid choking of recharge wells.
Recharge Shafts: For recharging the shallow aquifer which is located below clayey surface, recharge shafts are used. The size of recharge shaft is 0.5 to 3 m diameter and 10 to 15 m deep. After digging, these are back filled with boulders,gravels and coarse sand.
Spreading techniques: When permeable strata starts from top then this techniqueis used. Spread the water in streams/canals by making check dams and bunds. A percolation pond may be constructed in low-lying areas.
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