A 2 part poster to detail out borewells

1. boreWELLsThe borewell is perhaps the most common
source of water in urban India today.
Borewells or ‘tube wells’ are
manmade wells dug deep into the
ground to tap into water-bearing
soil or rock layers termed aquifers.
They typically draw water from “confined deep
aquifers”, i.e., rock layers deep underground,
where water is trapped under pressure between
the cracks of rocks and are formed over many
years, sometimes even centuries, due to water
percolating down the rock layers. Did you know
India has over 30 million borewells!
India is the largest user of
groundwater in the world, and
much of it is through borewell
extraction.
This was not always the case. Open wells used
to be the norm till around the 1970s when
borewell technology arrived in India. This was
when UNICEF brought borewell rigs to help
deal with water shortage.
Borewells source water from deep within the
ground, from the deeper aquifers. These rock
layers are at great depths and are usually less
permeable, and cannot soak up water. Thus
water stays trapped in cracks, surrounded by
rocks under pressure.
All open-wells and bore-wells get their water
from “aquifers”. An aquifer is a continuous
interconnected space underground within
which water resides and moves – this is
“groundwater”- this space can be between soil
particles or in cracks and fissures of rocks.
The open-well gets its water from the shallow
unconfined aquifer – groundwater which is
shallow and not under pressure. Borewells
typically go deep and get their water from
aquifers formed by cracks and fissures of rocks
where water is under pressure. Aquifers can
be local or regional. Aquifers get their water
from “recharge” – when rainwater seeps down
the earth and fills up all these spaces.
HISTORY
DIGGING A
BOREWELL
HOW IT WORKS
We can withdraw water from an open-well
when the shallow aquifer has water.
However, when all the water from the shallow
aquifer is pumped out for use, and there is
not adequate recharge from the rains, over time
the aquifer, and consequently an open-well,
will dry up. We can recharge the shallow aquifer
by redirecting water into an existing open-well.
Alternatively we can build an open-well only
to “recharge.” Such a well is called a recharge
well. The recharge well can also help us
prevent floods.
RECHARGE
WELLS
BOREWELL
STORIES
top
soil
WEATHERED ZONE
unconfined
shallow aquifer
LAKE
BOREWELLS
OPEN WELL RECHARGE WELL
STORM WATER DRAIN
deep
aquifers
FRACTURED ZONE
BEDROCK
SOIL
casing
borehole
water level
pump
WEATHERED
ZONE
WEATHERED and
fractured ZONE
HARD ROCK
India’s first
borewell rig,
brought by
UNICEF, is
still preserved
in Pune.
(above) A borewell rig (above)
and a borewell (left)
And by the late 1970s, borewells started
replacing open wells. They became popular in
cities because of the perception that borewell
water was cleaner and would be available
even during summers.
They however spurred a culture of exploiting
water as borewells make groundwater
“invisible”. As borewells dried up, deeper ones
were dug. Some even go down to 1800 feet,
but as you go deeper, the risks of chemical
contamination increase.
When a borewell is dug, such water-bearing
cracks are struck are various depths, and water
juts out at high pressure into the borehole. This
causes a sudden rise in water level in the
borehole. The level gets stabilised over time;
this stable level is called the static water level
of the borewell.
As the depth increases, the rock becomes even
less permeable and the number of cracks
decrease reducing the chance of finding water.
The vehicle that is
used to remove the
pump is aligned with
the borewell.
The delivery pipe is
connected to the winch
and wound up. The
water level in this 1400 ft
borewell stabilised at
300 ft, and you can see
that a signifant length
of the pipe is wet.
The new pump
is reassembled
and the
delivery pipe is
connected to
its first shaft.
The entire assembly is reinserted
into the borehole. Power cables
are attached and the delivery
pipe is unwound to its full depth.
At this site, the borewell pump
developed a problem and had to be
removed, refitted and re-inserted.