6. • Reduces water bills.
• Sets an example for students and parents.
• Improves groundwater table if rainwater is
recharged.
• Improves groundwater quality by dilution
(rainwater has nearly neutral pH and zero
hardness).
9. Rain Water Collected
From Both Sides of the
Roof
W
Rain Water
Collected From one
Side of the Roof
Amount of rainfall
(mm)
x =
W
Catchment Area (m2) Volume of water received
(Litres)
10. The water that leaves the rooftop may be 65 – 90% of
the water that falls on it
The water that leaves the rooftop may be 65 – 90% of
the water that falls on it
Roof material absorbs some water
More water loss if roof is flat
Evaporation losses
11. Remove leaves, plant debris,
bird and animal droppings, dead
rodents or birds
No tar / bitumen on the roof
No chemical pesticides or
fertilizers for rooftop garden
12. Transportation
Pipe size is calculated based on peak flow rates
(rooftop area and peak rainfall rate)
Gutter (open on top)
Downtake pipe (cylindrical)
PVC pipes preferred. Do not use lead pipes
13. Harvesting System
Broadly rainwater can be harvested for
two purposes
•Storing rainwater for ready use in
containers above or below ground
•Charged into the soil for withdrawal later
(groundwater recharging)
Source: A Water Harvesting Manual For Urban Areas
14. 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
15. Recharge to ground water is a new concept of
rain water harvesting and the 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.
16. Trenches:- These are constructed when the
permeable stram 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.
17. 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.
Recharge wells :- Recharge wells of 100 to 300 mm.
diameter are generally constructed for
recharging the deeper aquifers and water is
passed through filter media to avoid choking of
recharge wells.
18. Recharge Shafts :- For recharging the shallow
aquifer which are located below clayey
surface, recharge shafts of 0.5 to 3 m.
diameter and 10 to 15 m. deep are
constructed and back filled with boulders,
gravels & coarse sand.
Lateral shafts with bore wells :- For recharging
the upper as well as deeper aquifers lateral
shafts of 1.5 to 2 m. wide & 10 to 30 m. long
depending upon availability of water with
one or two bore wells are constructed. The
lateral shafts is back filled with boulders,
gravels & coarse sand.
19.
20. Population increase
Industrialization
Urbanization
(a) Increase in per capita utilization
(b) Less peculation area
In places where rain fed/ irrigation based crops
are cultivated through ground water
Decrease in surface area of Lakes, talab, tanks etc.
1
22. Rain Water Harvesting– AdvantagesRain Water Harvesting– AdvantagesRain Water Harvesting– AdvantagesRain Water Harvesting– Advantages
1.Provides self-sufficiency to water supply
2.Reduces the cost for pumping of ground water
3.Provides high quality water, soft and low in minerals
4.Improves the quality of ground water through
dilution when recharged
5.Reduces soil erosion & flooding in urban areas
6.The rooftop rain water harvesting is less expensive
& easy to construct, operate and maintain
7. In desert, RWH only relief
8. In saline or coastal areas & Islands, rain water
provides good quality water
24. Rain water is the ultimate 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 ultimate answer
3
26. ATTRIBUTES OF GROUNDWATER :
There is more ground water than surface water
Ground water is less expensive and economic
resource.
Ground water is sustainable and reliable source
of water supply.
Ground water is relatively less vulnerable to
pollution
Ground water is usually of high bacteriological
purity.
Ground water is free of pathogenic organisms.
27. Ground water needs little treatment before use.
Ground water has no turbidity and colour.
Ground water has distinct health advantage as
art alternative for lower sanitary quality surface
water.
Ground water is usually universally available.
Ground water resource can be instantly
developed and used.There is no conveyance
losses in ground water based supplies.
Ground water has low vulnerability to drought.
Ground water is key to life in arid and semi-arid
regions.
Ground water is source of dry weather flow in
rivers and streams.
28. Clamp gutters and down take pipes well
Keep gutters clean of leaves
See that leaves do not clog a down take pipe
(Jaali or leaf filter may be needed at rooftop discharge
point but this may also be a problem if leaf debris collects
on it and water stagnates on the roof)
Gutters and down take pipes should be gently sloping
towards the storage tank, so that there is no stagnation of
water in the pipe
30. The first rain carries with it a lot of filth from
the rooftop and dissolved air pollutants
This rainwater should be diverted away from
the storage tank using a first flush device.
Some filters have a first flush system
integrated in them
Check and clean first flush devices regularly.
First flush standpipe
31. Depends on
Rainwater availability
Water requirement
Budget (storage tank is most expensive part of (rwh system)
Available space and aesthetics
Excess water can be diverted into a groundwater recharge system
Do a water
audit to check
water
requirement.
32. Above ground
Ground level or Intermediate floor level
Just below roof
Below ground
Save on pumping cost
33. Durable and no leaks
Built on a strong and stable substrate that can support the tank filled with
water
Opaque – presence of light can cause algal growth in tank
Secure and impervious cover
Vents to be covered with insect proof mesh
Located as close as possible to demand and supply points to reduce
plumbing
34. • Overflow pipe should be provided close to the top, to reduce dead space.
• Overflow pipe diameter should be equal to inlet pipe diameter
• Overflow pipe should lead excess water away from the foundation of tank and other buildings.
Preferably the overflow should be led into a groundwater recharge system or a garden
• There will be sedimentation in the tank. Taps and pipes to draw water from the tank should
not be very close to the bottom to prevent sediments from entering the plumbing system
and clogging it.
35. If used for drinking, it is absolutely necessary to
check water quality in a lab and treat as required
36. Some changes may be required in
plumbing, if retrofit
Clean rwh system regularly
Rooftop everyday
Tank after a rainy season
Filter after a rainy season
38. I m really thankfull to my dear sir (Ayub sahib)
Who give me opertunity to present my skill
and guide me how to make assigment and
presentation .
