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E1-E2
Civil Technical
Rain Water Conservation &
Harvesting
WELCOME
• This is a presentation for the E1-E2 Civil Technical
Module for the Topic: Rain Water Conservation &
Harvesting.
• Eligibility: Those who have got the Upgradation to from
E1 to E2.
• This presentation is last updated on 19-3-2011.
• You can also visit the Digital library of BSNL to see this
topic.
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For internal circulation of BSNL only
AGENDA
Importance of Water for Life
Availability of Water in Nature
Advantage of Rain Water Harvesting
Different Harvesting Methods
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• jfgeu ikuh jkf[k;ks] fcu ikuh lCk lwuA
ikuh Xk;s u mCkjs] eksrh ekul PkwuAA
• Rahiman Pani Rakhiyo, Bin Pani Sab Soon
• Paani Gaye Na Ubre, Moti Maanas Choon.
• Rakhiyo – To Protect
• Soon – Empty
• Ubre – Not Survive
• Moti – Pearl
• Manas – Man, Choon – Hydrated Lime
Importance of Water
• Next to air, water is the only other resource in the
nature which sustains life on Earth. If we can not
live without air for more than a few minute, we can
not live without water form more than a few hour.
Life without water is impossible, with scare water
extremely hard and with water is blessing. In
reorganization of this fact Nature has covered two-
third of our planet with water.
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Importance of Water
• Indiscriminate mining of water due to rapid
industrialization as led to its acute shortage at an
alarming rate.
• Lowering of water table leading to drying up of bore
wells has become common occurrence.
• Government of India has since undertaken a
number of steps aimed at preventing its excessive
mining and harvesting and conservation.
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Availability of Water
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3%
97%
Fresh water
saline water
77%
11%
11%1%
Glaciers 77%
Deep Aquifers>800 m
11%
Deep Aquifers<800 m
11%
rivers,ponds,streams
1%
Availability of Water
• In fact the total freshwater available on earth is only 3%
as against 97% saline water in Oceans. Out of this 3%
fresh water, 77% water is in the form of glaciers and
icecaps, 11% water is in deep aquifers which is 800
meters below ground and only 12% is available for
drinking and other purpose out of which 11% is in
acquires which are up to 800 meters below ground and
remaining 1% is available in rivers, lakes, ponds and
streams.
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What is RWH
• Rain water harvesting is the technique of collection
and storage of rain water of surface or in sub-
surface aquifer by recharging it for future
requirement so that it is not lost as surface run-off.
Rain water is the purest form of raw water available
on the earth.
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Solution of Water Problems
• The solution of drinking water problem of the vast
majority of population in our country lies in the
appropriate use of Rain water harvested through
roof and from built up catchments where annual
rainfall is sufficient. It has been estimated that the
amount of rain water that falls on the terrace of a
medium house can take care of the drinking-water
requirement of an average family of four members
for one year.
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Advantages of Rainwater Harvesting
• Conservation of valuable ground water and
enhancing the availability.
• Recharge ground water level and improve it.
• Provides sufficient water for home needs
• Reduction in flooding and drainage problems.
• To arrest seawater ingress.
• Conserve urban water waste & controls soil erosion
• Improves the underground water quality.
• Saves the energy for lifting ground water.
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Rainwater Harvesting Systems :
• There are basically two main techniques for
harvesting rainwater: Conservation by providing
storage tank on the ground or under ground and
recharge of aquifer.
• A rain water harvesting structure can incorporate
either of these two techniques or a combination of
both depending upon various factors as shown (In
next slide).
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Rainwater Harvesting Systems
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RAIN WATER
HARVESTING
SYSTEMS
CONSERVATION
GROUND
WATER
RECHARGE
STORAGE
TANK
CHECK
DAMS
LAKES &
PONDS
CONSERVATION
& RECHARGERECHARGE
PIT
RECHARGE
TRENCH
RECHARGE
SHAFT
RECHARGE
BORE WELL
DUG
WELL
CAVITY
WELL
HAND
PUMP
Methods of Rainwater Harvesting
Recharge Pit
• It is suitable for areas where sandy formations occur
within 1-2m from the ground surface.
• This is ideally suited for small buildings up to 100 sq. m
roof top area.
• It can be circular, square or rectangular in shape.
• These are generally constructed 1-2m wide and 2-3m
deep.
• After excavation the pits are refilled with pebbles and
boulders.
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Methods of Rainwater Harvesting
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RECHARGE
PIT
Methods of Rainwater Harvesting
Recharge Trench
• It is suitable when permeable strata of adequate
thickness are available at shallow depth and the roof
area of the building is 200-300sqm.
• Recharge trench can be of any dimensions.
Generally it is 1-1.5m deep, 0.5-1m wide and of any
length depending upon the availability of water to be
recharged.
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Methods of Rainwater Harvesting
• Recharge trench can be straight, zig-zag, L-
shaped, U shaped.
• The recharge trench should be filled with filter
media which can grade from boulders (5-20cm) at
the top for filtration of water.
• The sides of the trench should slope at low angle
for stability.
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Methods of Rainwater Harvesting
For internal circulation of BSNL only
Methods of Rainwater Harvesting
• Recharge Shaft:
• This is the most efficient and cost effective
technique to recharge unconfined aquifer overlain
by poorly permeable strata.
• This is like an open well but filled with filter media.
• Diameter of the shaft generally varies from 1-3m
depending upon the availability of the water to be
recharged.
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Methods of Rainwater Harvesting
• It is constructed where the aquifer to e recharged is
located at medium depth.
• The recharge shaft end in permeable strata to be
recharged. It may not touch the water table.
• In the upper portion of 1-2m depth, the brick
masonry work carried out for the stability of the
structure.
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Methods of Rainwater Harvesting
For internal circulation of BSNL only
Methods of Rainwater Harvesting
Recharge/Injection well
• This is used to recharge deep aquifer or where
multiple aquifers are met interspersed with
impervious strata.
• In case of recharge well single diameter pipe
assembly is used and it should have the provision
of slotted pipes against the water bearing strata.
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Methods of Rainwater Harvesting
• The rainwater is allowed to pass through the filter
media before it is channeled to the well under
gravity flow conditions.
• The number of recharging wells depends upon the
roof top area and aquifer characteristics.
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Methods of Rainwater Harvesting
For internal circulation of BSNL only
Methods of Rainwater Harvesting
For internal circulation of BSNL only
Methods of Rainwater Harvesting
Dug Well
• Dug wells may be utilized as recharge structure
after cleaning & de-silting the same.
• A filtration chamber may be constructed so that the
water can be made silt free before entering the dug
well.
• The recharge water is guided through a pie to the
bottom of the dug well and it is converted into dug-
cum-bore well.
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Methods of Rainwater Harvesting
• It is suitable for large buildings preferably having
the roof area more than 1000sqm from where the
rain water can be diverted and recharged.
• Periodic chlorination should be done for controlling
the bacteriological contaminations.
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Methods of Rainwater Harvesting
Abandoned Tube-wells/Hands Pumps:
• These water abstraction structures act as good
recharge structure.
• The hand pump is suitable for small building
having roof area up to 150sqm.
• Water is diverted from the roof top to the hand
pump through pipe of 100 mm dia.
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Methods of Rainwater Harvesting
Contour Bunds
• These are suitable in low rainfall areas where
monsoon runoff can be impounded by constructing
bunds on the sloping ground all along the contour of
equal elevation.
• Flowing water is intercepted before it attains the
erosive velocity by keeping suitable spacing
between the bunds.
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Methods of Rainwater Harvesting
• Spacing between the two contour bunds depends
on the slope of the area as well as the permeability
of soil.
• Contour bunding is suitable on lands with moderate
slopes without involving terracing.
• Contour bunds are effective methods to conserve
soil moisture in watershed for long duration.
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Cost of Rain water Harvesting
• The cost of implementation of rainwater harvesting
systems in a house/flat complex will vary from
Rs.5000 – Rs.50,000 depending on the size of the
premises as well the nature of the soil. Once put in
place, the harvesting structure do not require any
serious maintenance and hence there is no
recurring expenditure involved.
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For internal circulation of BSNL only