2. 2
INTRODUCTION
Rainwater harvesting means,“Delibarate collection
and storage of rain water”.
An average of 8% to 12% of total rainfall
recharges ground water aquifers.
The technique of rainwater harvesting involves
catching the rain from localized catchment surfaces
such as roof of a house, plain and sloping ground
surface etc..
3. 3
Ancient Methods Of RWH
From Roof tops & stored in tanks
individually,
In Kunds of Thar Dessert,
By Kaul Irrigation,
By Bamboo Rainwater Harvest
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CONTOUR BUNDS
Adopted in low rainfall area.
Constructed across the slope the land.
Not recommended for clayey soils.
Surface Spreading Techniques
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GULLY PLUGS, NALA BUNDS AND
CHECK DAMS
Constructed to impend the flow of surface
water in the stream channel.
Water is retained for longer duration in
pervious soil or rock surface.
Generally constructed across bigger streams
having gentle slope.
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PERCOLATION PONDS
Prevalent in alluvial and hard rock
formations.
These are submerging highly
permeable land.
Efficiency and feasibility in hard rock.
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RECHARGE BASINS
Constructed parallel
to ephemeral or
intermittent stream
channels.
They are excavated
or are enclosed by
dykes and levees.
Water contact area-
75% to 90% of
total recharge area.
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INJECTION
WELLS/RECHARGE WELLS
Similar to bore wells constructed for
augmenting GW storage in deeper
aquifer.
Advantageous when land is scarce,
desaturated and to arrest the ingress
of sea water
Sub Surface Techniques
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GRAVITY HEAD
RECHARGE WELLS
Existing dug/tube/bore wells used
alternatively as recharge wells.
Used in areas where de-saturation of
aquifers taken place.
Soil moisture losses get reduced.
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RECHARGE PIT
Excavated pits.
Deeper than
recharge basins.
Infiltration occurs
laterally through
walls of the pit.
Recharging capacity
increases with c/s
area.
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RECHARGE SHAFTS
Most efficient and
cost-effective to
recharge aquifers
directly.
Recharge shafts
constructed to
augment recharge
into deeper aquifers
having low
permeability.
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GRONDWATER CONSERVATION
TECHNIQUES
Intended to retain GW for longer period.
Techniques involved:-
GW Dams/sub-surface dykes/bandharas.
These are basically ground water conservation structures
and are effective to provide sustainability to ground
water structures by arresting sub-surface flow. A sub-
surface dyke / ground water dam is a sub-surface barrier
constructed across a stream channel which retards the
natural ground water flow and stores water below the
ground surface to meet the demands during periods of
need.The main purpose of ground water dams is to
arrest the flow of ground water out of the
watershed/sub-basin and increase the storage within the
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ROOFTOP RAINWATER
HARVESTING
Involves collection of water from
the roof and stored into the tank.
Collection of water from the roof
and used to recharge GW table.
22. 22
RTRWH USING STORAGE
TANKS
These systems are designed to
support the drinking and cooking
needs of the family at the
doorstep.
collected water in storage tank is
used during the periods of
scarcity.
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RTRWH
Components :-
1. Roof catchments.
2. Drain pipes.
3. Gutters.
4. Down pipe.
5. First flush pipe.
6. Filter unit.
7. Storage tank.
8. Collection sump.
9. Pump unit.
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RRHS
Advantages:-
1. Rainwater Run-off can be harvested and
utilized.
2. Reduces drainage congestion in urban
areas.
3. Help to recharge groundwater.
4. Economical and eco-friendly.
5. Improves quality of ground water through
dilution.
25. 25
RAINWATER QUALITY AND
HEALTH
Rainwater is often used for drinking and
cooking and so it is vital that the highest
possible quality standards are met.
It does not meet the WHO water quality
guidelines,hence it can be used other than
drinking.
Australian government has given the all
clear for the consumption of rainwater
‘provided the rainwater is clear, has little
taste or smell, and is from a well-maintained
system.
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CONCLUSION:
India reaches much of its rainfall in just 100 hrs in a
year usually during monsoon period. If this water is
not captured or stored, the rest of the year
experiences a precious situation manifest in water
scarcity.
More and more schemes of water supply being
undertaken in rural areas only on the basis of
groundwater resources. However, no steps are taken
to recharge the groundwater reservoirs. Hence, in it
is essential to take necessary steps to recharge
groundwater reservoirs by percolation tanks, rock fill
dams, contour trenching and bunding, check dams,
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CONCLUSION (Cont..d)
Due to urbanization, the rate of infiltration has been
reduced drastically and most of the runoff is
wasted. Hence individual rainwater harvesting
schemes are to be undertaken so that water is
collected from the roofs and surrounding areas and
can be used throughout the year for all purpose
except drinking and cooking and hence, load on
water supply schemes of local authorities can be
reduced.
For successful implementation of any method of
rainwater harvesting, active participation of public is
a must.
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REFERENCES:-
Making water everybody’s business –
practice and policy of water
harvesting, edited by Anil Agarwal,
Sunita Narain and Indira Khurana.
(Center for science and environment).
www.aboutrainwaterharvesting.com
