Do-It-Yourself

RECHARGE WELL

Rainwater Harvesting Guide

3 feet diameter and20 feet deep well

Recharge Well Diagram with details

Sir Vishweshwaraiah Rainwater Harvesting Park 8th Main, 40th Cross,

5th Block, Jayanagar, Bangalore.

How much will it cost

4 feet diameter and25 feet deep well

5 feet diameter and30 feet deep well

What does this cost include?

Digging labour Rings - procurement + transportation40mm jelly - placed in annular gap between pit and ringsConcrete slab/metal grille - with manhole for maintenanceDumping of excavated soil - (this can be very expensive in certain parts of Blr !!)

Did you know?

This activity (of digging Recharge wells) is providing employment to the Bovi community - the traditional well diggers

31st December 2011 is the deadline for Rain Water Harvesting implementation as per BWSSB regulations.

Rules: Storage/Recharge recommended by BWSSB per sq. mt. of roof area is 20 litres and for paved area is 10 litres.

Bangalore is growing at an unprecedented rate, and its sprawling expansion outpaces the public utility’s ability to accommodate skyrocketing demand for water and sanitation services. It is increasingly common for new residential communities to assume total management for their own water and sanitation services through their resident welfare associations. Most of these depend on borewells and tankers, which they sooner or later realize is not a sustainable option. Groundwater recharge, one of the forms of Rainwater harvesting, can be instrumental in efforts to achieve long-term water security. By taking water out of over-stressed storm drains and replenishing them into shallow aquifers, groundwater recharge wells effectively raise water tables and reduce the intensity of flooding in a layout.

The diagram above explains Bangalore’s geology- below the top soil is the weathered zone, which is made of rock and behaves like a sponge. This layer changes from area to area. Then comes the bed rock layer. The bed rock is not a monolithic layer; the rocks have cracks and fissures through which water passes and gets accumulated inside the rock. This is a deep acquifer. Borewells break into the bed rock and taps into the water there.

Recharging is process of letting water back into the earth. A recharge well is a big hole through which water goes into the sponge or weathered zone. Recharge wells are dry wells, in the sense that they send water down in one direction, and do not yield water (initially at least) themselves.

Imagine a dry sponge and you are pouring water through a hole into the sponge. The water soaks up the sponge. Sooner or later, the sponge will hit a saturation point. At that point water appears back in the recharge well and it starts yielding. When this happens (all recharge wells have this potential) a recharge well becomes an open well.

What is recharging?

Will I get this water back?

How do shallow acquifers form?There are cases where locally there will be a layer below the open well in the sponge where water from the recharge well does not go into the sponge itself. Instead it builds an underground lake and that becomes the shallow acquifer. The recharge well then starts yielding.

Over a very long time, deep acquifers can get saturated too, and this can build a shallow acquifer above. As more and more water is continually drawn from the acquifers, yields (for borewells or open wells) tends to fall off over time, unless recharging is being done.

Why should I do ground water recharge?

Did you know?

Residents who have done continuous recharge for a period of 2-3 years have revived wells now that yield water all through the year. These houses can do without corporation water supply.

How can I clean/ filter the water before

sending it to the Recharge Well?

The making of a Recharge Well

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3 4

5 6

7 8

Is it safe to dig a well in a Residential Area?

Excavation: Dig a well having dimension 2” more in diameter, than the RCC rings

Place a strong perforated RCC cover or a grill for safety. The water should be filtered to remove the silt and leaves before it enters the well through an internal pipe.

Lower the RCC rings one by one into the well . Place the rings one above the other.

The Jelly is then lowered into the well and packed between the rings and the well to ensure the rings are in place

For large quantities of water (industries, layouts...), a Percolation test should be done with the first well, to see how fast the water enters into the ground, and thus the number of wells necessary can be known.

A Recharge Well can be easily constructed using concrete ringsof diameter ranging from 2 feet to 6 feet and depth of 20 feet to 30 feet to store large volumes of rainwater and recharge the groundwater under good hydrostatic pressure. About 70% of the water will percolate vertically, the other 30 % horizontally through the holes provided in the rings. The soil profile of the site helps to determine the depth of the well, its bottom should reach a critical level of the weathered zone, where the water can easily percolate.

40 mm Jelly

Place all the rings and center them Complete the well by packing Jelly all around the RCC rings

Identify the catchment area and ensure that it is clean and unpolluted, make sure there is no sewage close by. Especially when water is picked up from lawns it should be free from fertilizer and pesticide. The golden rule for recharge is put in only what you can take out and drink.

The rooftop rainwater, water runoff from the storm drains is filtered by placing a slab and leading the water into a pipe which has been covered with mesh and jelly to purify the water.