The document discusses rain water harvesting as a solution to water shortage problems caused by increasing population, industrialization, urbanization, and decreasing surface water areas. It states that rainwater harvesting helps overcome water scarcity by conserving groundwater through recharging aquifers with harvested rainwater. The typical roof top rainwater harvesting system consists of a roof catchment, gutters, down pipes, a first flush system, a filter unit, and a storage tank. Rainwater harvesting provides clean water and has advantages of low cost, ease of construction and maintenance, and drought mitigation.

1. RAIN WATER HARVESTING
BY
KRISHNA VAMSY

2. REASONS OF SHORTAGE OF WATER
• POPULATION INCREASE
• INDUSTRIALIZATION
• URBANIZATION
- INCREASE IN PER CAPITA UTILIZATION
• IN PLACES WHERE RAIN FED/ IRRIGATION BASED
CROPS ARE CULTIVATED THROUGH GROUND WATER
• DECREASE IN SURFACE AREA OF LAKES, TANKS ETC.
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4. WHAT IS THE SOLUTION ?
• RAIN WATER IS THE SOURCE OF FRESH WATER
• POTENTIAL OF RAIN TO MEET WATER DEMAND IS
TREMENDOUS
• RAIN WATER HARVESTING HELPS TO OVERCOME WATER
SCARCITY
• TO CONSERVE GROUND WATER THE AQUIFERS MUST BE
RECHARGED WITH RAIN WATER
• RAIN WATER HARVESTING IS THE ANSWER3

5. WHY RAIN WATER BE HARVESTED
• TO OVERCOME THE SHORTAGE OF WATER.
• TO REDUCE WATER TABLE DEPLETION.
• TO IMPROVE THE QUALITY OF GROUND
WATER.
• TO REDUCE PRESSURE ON OTHER WATER
RESOURCES.

6. Rain Water Harvesting?.Rain Water Harvesting?.
• Rain Water Harvesting RWH- process of collecting,
conveying & storing water from rainfall in an area – for
beneficial use.
• Storage – in tanks, reservoirs, underground storage-
groundwater
•

7. RAIN WATER HARVESTING
TECHNIQUES :
There are two main techniques of rain water
harvestings.
Storage of rainwater on surface for future use.
Recharge to ground water.
The storage of rain water on surface is a
traditional techniques and structures used were
underground tanks, ponds, check dams, weirs
etc

8. RAIN WATER HARVESTING
Rain
Roof Top
Filtration
or
Recharge to ground water
Storage
Rooftop Water

9. RECHARGE TO GROUND WATER:
Structures generally used are
Pits :- Recharge pits are constructed for
recharging the shallow aquifer. These
are constructed 1 to 2 m, wide and to 3
m. deep which are back filled with
boulders, gravels, coarse sand.

10. Technology of Rainwater Harvesting

11. Trenches:- These are constructed when the
permeable stream is available at shallow depth.
Trench may be 0.5 to 1 m. wide, 1 to 1.5m.
deep and 10 to 20 m. long depending up
availability of water. These are back filled with
filter materials.
Dug wells:- Existing dug wells may be utilised
as recharge structure and water should pass
through filter media before putting into dug
well.

12. TRENCH

13. Hand pumps :- The existing hand pumps may be
used for recharging the shallow/deep aquifers, if
the availability of water is limited. Water should
pass through filter media before diverting it into
hand pumps.

14. THE TYPICAL ROOF TOP RAIN
WATER HARVESTING SYSTEM
COMPRISES
• ROOF CATCHMENT
• GUTTERS
• DOWN PIPE & FIRST FLUSHING PIPE
• FILTER UNIT
• STORAGE TANK
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16. ROOF CATCHMENT
The roof of the house is used as the catchment for
collecting rain water.
The style,construction and material of the roof effect its
sustainability.
Corrugated iron sheet, asbestos sheet, tiles or concrete can
be utilized for harvesting rainwater.
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17.  THE ROOF CATCHMENT ARE SELECTIVELY CLEANER
WHEN COMPARED TO THE GROUND LEVEL CATCHMENT
LOSSES FROM ROOF CATCHMENT ARE MINIMUM
NO CHEMICAL CONTAMINATION & ONLY REQUIRED
FILTRATION
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18. GUTTERS
GUTTERS ARE CHANNELS FIXED TO THE EDGES
OF ROOF ALL AROUND TO COLLECT &
TRANSPORT THE RAINWATER FROM THE ROOF.
GUTTERS CAN BE MADE IN SEMI-CIRCULAR AND
RECTANGULAR SHAPE WITH CEMENT PIPE, PLAIN
GALVANIZED IRON SHEET, PVC PIPES, BAMBOOS
ETC. USE OF LOCALLY AVAILABLE MATERIAL
REDUCE THE OVERALL COST OF THE SYSTEM.
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19. DOWN PIPE
IT IS THE PIPE WHICH CARRIES THE
RAINWATER FROM THE GUTTERS TO THE
FILTER & STORAGE TANK. DOWN PIPE IS
JOINED WITH THE GUTTERS AT ONE END &
THE OTHER END IS CONNECTED TO THE
FILTER UNIT OF THE STORAGE TANK. PVC
OR GI PIPE OF 50MM TO 75MM (2 TO”) ARE
COMMONLY USED FOR DOWN PIPE.
BAMBOO CAN BE ALSO USED WHEREVER
AVAILABLE AND POSSIBLE20

20. FIRST FLUSH PIPE
DEBRIS, DUST & DIRT COLLECT ON THE ROOF
DURING NON RAINY PERIODS. WHEN THE FIRST
RAIN ARRIVE A FIRST FLUSH SYSTEM
ARRANGEMENT IS MADE TO AVOID THE
ENTERING UNWANTED MATERIAL INTO THE
FILTER MEDIA & STORAGE TANK. THIS IS A
SIMPLE MANUALLY OPERATED ARRANGEMENT
OR SEMI-AUTOMATIC SYSTEM WITH A VALVE
BELOW THE ‘T’ JUNCTION
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21. FILTER UNIT
THE FILTER UNIT IS A CONTAINER OR CHAMBER
FILLED WITH FILTER MEDIA SUCH AS COARSE
SAND, CHARCOAL, COCONUT FIBER, PEBBLES &
GRAVELS TO REMOVE THE DEBRIS & DIRT FROM
WATER THAT ENTERS THE TANK. THE FILTER
UNIT IS PLACED OVER THE STORAGE TANK OR
SEPARATELY. IT MAY BE OF FERRO CEMENT
FILTER UNIT, ALUMINUM, CEMENT RINGS OR
PLASTIC BUCKET ETC.
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22. STORAGE TANK
IT IS USED TO STORE THE WATER THAT IS
COLLECTED FROM THE ROOF THROUGH FILTER.
THE STORAGE TANK IS PROVIDED WITH A COVER ON
THE TOP TO AVOID THE CONTAMINATION OF WATER
FROM EXTERNAL SOURCES.
 THE STORAGE TANK IS PROVIDED WITH PIPE
FIXTURES AT APPROPRIATE PLACES TO DRAW THE
WATER TO CLEAN THE TANK & TO DISPOSE OF
EXTRA WATER. A PROVISION FOR KEEPING THE
VESSEL TO COLLECT THE WATER IS TO BE MADE.
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24. Water Source Setup Cost Running Cost Yield Applicable in
Tubewells Medium Medium Medium Places with
Deep Aquifers
Hand-dug
wells
Low Medium Low-Medium Places where
water table is
not lower than
six metres
Reverse
Osmosis
High High High Only in Urban
regions
Rainwater
Harvesting
Low-Medium Low-Medium High Only in regions
which receive
Comparison With Other MethodsComparison With Other Methods

25. No land is wasted for storage purpose and no
population displacement is involved.
Improves the quality of ground water through
dilution when recharged
Reduces soil erosion & flooding.
Mitigates the effect of drought.
The rooftop rain water harvesting is less expensive &
easy to construct, operate and maintain
In saline or coastal areas & Islands, rain water
provides good quality water
ADVANTAGES:

26. DISADVANTAGES:-
Unpredictable rainfall
Storage limits
Regular maintenance

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