Borewell: A discussion
Nov 21 2019
Water is a vital resource for the living, sustainability and growth of all living organisms. The water resource data gives a good picture of the availability of potable water on the surface of the earth which is nearly 0.3% of 2.5% of total available water on earth. The groundwater is easily available in all season of the climate unless it's not a depleted aquifer. But, digging a bore well is quite costly and the customer is always unsure of the availability of potable water. About 30 percent of the total farmers in South India use borewells as their only resource of water for cultivation. While not many are knowledgeable on the recharge of groundwater and the lifetime of the Borewell.
A borehole is dug deep into the portion of soil or the rock strata which contains ample quantity of water. This portion of soil where water is available is called as aquifers which are formed as a result of water seepage into the ground for many years or centuries. In Bengaluru, water is available in decent depths ranging from 250- 500 feet below the strata. And due to population explosion and rapid urbanization, these depths are increasing day by day. Previously, bore well water was thought to be 100 percent safe and portable but now, it's not. Chemical contamination increases as the bore well depth go high and must be tested before drinking from a new borewell.
Understanding the mechanism of borewell:
- As a continuous method of permeation and percolation, water has seeped into the highest depth it can go.
- Here, its stopped under high pressure due to the impermeable rocks and exerts nominal pressure on the natural walls of the aquifer.
- When a borehole is dug into the aquifer, the water finds a path for itself to release the energy from the initial pressure. So, it rises on the path of the borehole.
- The water level in the borehole is extremely fluctuating for a couple of days and is stable over a period of time. The stable water level is called as the static water level of borewell.
- The dug borehole is provided with casing to prevent the collapse of surrounding soil particles and clogging the borewell. This casing pipe is made of cast iron or steel to withstand the lateral forces of soils.
- The casing pipe installed is given till the hard strata of the soil. It is half the diameter of the borehole and should not be greater than 24 inches.
- A submersible pump is installed at the level just below the of a layer of hard strata where the first crack was made to dig the aquifer.
- The pump has a delivery pipe associated with it which transfers the water pumped to the surface of the ground.
- The pump is well connected with wires and electrical fixtures for its working.
- Water is drawn from the aquifer on switching on the submersible pump.
- The aquifer gets water from underwater flow from neighbouring water bodies which is called as the underground flow.
- The aquifer also gets water recharged from the surface flow but its tedious and time taking as the soil permeability for water is low.
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