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

Recharge wells are one of the best options for augmenting underground water holding. This article explains the site specifications and techniques used in the construction of these wells
Recharge well with gravel and sand bed to filter rainwater. Image courtesy India Water Portal Recharge well with gravel and sand bed to filter rainwater. Image courtesy India Water Portal

 

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.

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