Laughing Waters Ground Water Recharge
Why do we need it ?
Rainwater harvesting at the layout level will essentially aim at recharging the groundwater close to the borewells. Our current bore well runs for over 8 hours. With more residential homes , the need for water is more. By channelising the Rain water into empty plots, the Ground water gets Recharged.
What are the solutions ?
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A very simple and efficient way to help the rainwater to percolate into the ground is to build small earth bunds ( 2’ wide, 2’ high) around each empty plot. These natural walls will prevent the rainwater to escape in the drains and let it infiltrate into the ground.
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Close to the working bore well, two recharge wells can be dug. A recharge well is 3’ diameter, 20’ deep made with RCC rings. The hydrostatic pressure of the water entering the well allows it to percolate efficiently into the ground. The water will then reach the same aquifer than where the bore well is taping and increase the level of the groundwater table in the area. Depending on the percolation rate of the water in the wells and the amount of water overflowing, we will be able to decide if it is necessary to dig more recharge wells in that area. The yield of the bore well and its water composition should be checked before and after the first rainy season. Depending on the results, we will know how effective the artificial recharge is in this place.
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A check dam 1’ high and a silt trap 1’ deep in front of the well will allow the solid particles to settle. The water will enter the well through a 4” PCV pipe provided with a mesh as shown on the section below
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Material
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Quantity
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Cost per unit (Rs)
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Total cost (Rs)
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4 “ PVC pipes
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1 lenghts (6 metres)
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600
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600
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Recharge well
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3’dia 20’ deep / 2 no
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19,000
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38,000
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Check dam
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2”x3’x1’ / 2 no
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500
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1,000
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Silt trap
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3 ft x3 ft x 1 ft / 2 no
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1,500
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3,000
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Consultancy
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|
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6,000
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TOTAL
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48,600
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What do we do about Water on Storm Drain?
In the same drains a slab can be removed every 10 feet and a small recharge pits can be dug. This is a way to increase the rainwater percolation in a decentralized manner.
What are the plans to Recharge the Park area?
The water falling on the park can be collected at the end of the same. The normal annual rainfall in Bangalore south is 870 mm. As the park area is around 8,000m², assuming a runoff coefficient of 0.6, 8000x0.870x0.6 = 42 lakhs litres of rainwater can be collected every year.
This water can be led in a water body wich would serve two purposes. Increase the groundwater recharge close to the second borewell and create a complete natural ecosystem in the park
The capacity of the lake would be around 3 lakhs litres. An overflow pipe will lead excess water back into the drain. Part of the year, the water will attract birds and create a cooler climate. It will also increase the soil moisture of the park, which helps the plants and trees to grow better. Guppies (small fishes eating mosquito eggs) can be introduced in the lake, so that the mosquito breeding is naturally controlled.The recharge well in the centre to send water deeper in the ground to recharge the aquifer in this area. If the lake becomes dry during the rainy season, this area can be used as playground as gentle slopes and stairs are provided. WE will have to arrive /estimate the cost of the above.
Who are the experts?
Experts from RainwaterHarvesting have helped us with the Design and implemetation. For more information on rainwater harvesting for a house the Rainwater club can be contacted : www.rainwaterclub.org ; zenrainman@gmail.com.
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