Recharge Wells

Ground water recharge is the act of augmenting the groundwater table by means of recharge wells, check dams, contour bunding, injection wells, etc.

In this case, the rainwater flowing on the surface (surface run off) is trapped and injected into the soil.

The shallow aquifer is augmented by constructing check dams at suitable contours or by sinking recharge wells. Technical and contour surveys are carried on to identify suitable locations and depth (in case of recharge wells). ‘Slug tests’ or ‘Pumping In’ tests are carried out for large campuses. Recharge wells are sunk at suitable depths so that enough pressure and porosity is reached for optimum recharge.

Ground water recharge; General principles:

Typical Schematic of a recharge well

Excess run-off from clean surfaces, run-off from other surfaces such as roads, garden area etc can then be redirected for groundwater recharge. In the context of Bangalore, the most effective recharge structure has been found to be a recharge well whose depth is a minimum of around 20 feet. These recharge wells recharge the shallow aquifer. Water needs to be desilted adequately before allowing the water into recharge wells. The location of the recharge wells need to be chosen strategically – both where significant run-off water passes through the recharge well location and which is close to existing borewells. Recharge wells, over time will help replenish groundwater. If the ground water table rises above the bottom of the recharge well, the recharge well can be used as a withdrawal well. The diagram below illustrates the principle of recharge.

Case 1: Recharge well does not hit water:

In this case, the recharge well behaves as stated above. The water fed into the well will slowly replenish the ground water table. If the location of recharge well is such that, it is in the radius of 5 to 10 feet from a yielding borewell, there is a more than 60% chance of the recharged water reaching the source of the borewell water.

Case 2: Recharge well hits water:

In this case, the water from the well can be used after testing. Either the existing plumbing can be retrofitted to accommodate supply from the recharge well or a separate plumbing line can be created. The water from recharge well can act as additional source of water.

Deep Aquifer recharge/Borewell Recharge

Here either the rooftop water or the surface water is injected into either old tube wells or newly sunk tube wells. Sufficient care is taken so that the soil/rock stratum below the tube well casing is not disturbed.

Note:

There is a good possibility that there may not be any water when the recharge well is being dug, but over few years owning to sustained recharge, the recharge well may start yielding.