Augmenting groundwater: The basics on how to construct a recharge well

Open wells have a major role to play in the artificial recharge of groundwater. Rooftop rainwater and surface water flowing in storm water drains can be filtered; the silt removed and allowed to recharge the open wells.

If you are building on a new site do not forget to consider digging an open well. No, It need not be like the magnificent stone structure shown alongside. It can be of RCC rings, only a metre in diameter and about 6 metres deep.

Materials required

• Ferro cement rings which are available in the following sizes – 2’, 2 ½’, 3’, 4’ and 6’ diameter
• Boulders for lining the pit

Site specification

• Should have sufficient catchments
• The substrate should not be hard rock

Note

• Concrete ring-wells of diameter ranging from 2 to 6 feet and depth of 20 to 30 feet store large volumes of rainwater and recharge the groundwater under good hydrostatic pressure
• The soil profile determines the water holding capacity and the depth of wells

Construction technique

Step 1

• Identify the catchment area
• Ensure that it is clean and unpolluted
• Determine total runoff and maximum runoff from rainfall data

Step 2

• Identify natural drainage flow channels (storm drains) or create artificial drainage channels
• Locate the position of recharge well in the channel or off the channel

Step 3

• Dig a pit having dimension 2” more in diameter, than the rings
• Dig the pit till the aquifer is reached
• Pack the pit with 1” thick layer of boulders
• Place the rings one above the other in the pit

Step 4

• Cover the pit with percolated cover
• Make arrangements to remove silt and leaves before water enters recharge well
• Monitor the rate of recharge and decide on the number of recharge wells necessary for the catchments

Cost and caution - Recommendations

• By making some experiments to observe the rate of infiltration of water, you will be able to decide the number of recharge wells necessary for the catchments
• Water should also be allowed to flow into the well gently from the sides or as a spray. This prevents the churn up of silt which otherwise causes air bubbles to block the natual pores in the soil.

What else is possible

• With a good aquifer, the ground water table should rise and the recharge well can become a withdrawal well
• Recharge wells are excellent for recharging bore wells
• Rooftop rainwater is ideal for such recharge as it is easy to keep roofs clean

Cost    

Digging a new recharge well costs around Rs. 8,000 to Rs. 12,000 depending on the diameter and depth.

Caution

• The catchments should be clean and unpolluted
• Do not let contaminated water get into the well
• Regularly monitor the water table for both water levels and water quality
• Regular maintenance of the channel is very important

Trivia: A 3 feet diameter and 20 feet deep well can recharge ground water from nearly 1000 square metres of area which in a normal year of rainfall (900 mm) means about 1 million litres of water.