For sustainable borewells

We must allow a million solutions to bloom and turn around our overexploitation of groundwater. By S. Vishwanath

If you are in the city you cannot but be touched by borewells and the waters they provide. Many apartments have more than one. Even individual residences dig one to access water for construction and then as a back-up to city water lines.

Private water tankers fill up and race around the city with waters from borewells, emptying endlessly into large thirsty sumps. The city of Bengaluru alone is estimated to have close to 400,000 borewells.

Unlike the open dug well, borewells tend to tap into fossil water. Water accumulated over years. Though direct recharge of the borewells is done, it is a difficult process.

Borewells have reached depths of 1,800 feet in the surrounds of Bengaluru and 900 to 1,000 feet is becoming the norm. Frequently they do not strike water and if they do, the water does not last very long. What then is the solution to this massive problem?

As policy and law tries to grapple with regulations, from the field comes a series of explorations in the jugaad spirit.

First, ‘filter’ borewells are making a comeback. These are small borewells which do not go very deep, at a maximum of 200 feet. They are drilled into the weathered rock and at best the first fissure in hard rock. They have a slotted casing to allow the phreatic, unconfined aquifer water, which is annually replenished to come into them. They tap this water using small-capacity pumps. They draw less water but are less costly and can be easily recharged.

Innovative capping

Second, is the capping of deep, dry borewells. Using an innovative method, volleyball or football bladders are introduced into the deep borewell usually just after the first yielding fissure. They are then filled with air and then sealed with white cement, reducing the depth of the borewell. This method eliminates the loss of water from the first fissure into deeper fissures, thus giving life back to old borewells.

Third, is a system which uses a device to punch slots in the casing of the borewell in the shallow weathered portion to allow the unconfined aquifer water to come into the borehole and then be pumped for use. Old borewell casings did not have slots and did not allow shallow aquifer to seep into the borehole. This method of making slots in the casing helps to address the problem.

Camera inspections

All the above three methods use camera inspections to help identify groundwater sources and help shift to the shallow, unconfined aquifer as a source.

India has the largest dependence on groundwater in the world. We pull out 250 billion cubic metres of groundwater annually. By using rainwater harvesting systems, recharging the shallow aquifers, cleaning and desilting water bodies and above all placing a cap on demand which is less than the annual replenishment by rain, we can turn around our overexploitation of groundwater .

For this we must allow a million solutions to bloom and listen to those with skin in the game for solutions. That would be groundwater and water wisdom.

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