Water harvesting principles and water harvesting methods.Run off methods and Rooftop harvesting methods

1. WATER HARVESTING

2. WHAT IS WATERHARVESTING?
•The term ‘water harvesting’ is usually taken to
mean the immediate collection of rainwater running
off surfaces upon which it has fallendirectly.
•This definition excludes run-off from land
watersheds into streams, rivers, lakes, etc.
•Hence it is the catching of rain water when it falls
and storing to use during the non rainyseason.

3. PRINCIPLES OF WATER HARVESTING
 Studying of Rainfall and suitable Locations
 Construct small structures which can be constructed
by locally available materials
 Start constructing from high point and gradually come
down
 Stream should be made of water rather than runoff
and erode lot of soils.

4.  Create a storage so that the harvested water be
allowed for percolation to take place
 Always plan for an overflow route and manage that
overflow as a resource
 Using this harvested water multiple purposes can
be served
 Continually reassess the system such that any
shortage can be met with in the next face in 2nd
principle

5. THE TECHNOLOGY OF RAIN WATER
HARVESTING
•Can be divided according to the purpose and
the source of collecting water.
•Methods
-Roof top harvesting
-Run off harvesting
•These methods can be selected considering
the purpose, the typeand quantityof
storage, Catchment state.

7. •Roof top harvesting-
This method include the catchmentarea as the roof top
in rural and urban area.
This include Rooftop of
houses,flats,factories,offices,complexes.

8. •Runoff harvesting
Here the runoff water is collected-
Gardens,driveways,landscapes,open fields,parks,roads
and pavements and otheropen areas of the
environmentcan be used to harvest the rain water
runoff.
Using this method, it is possible tocollectwater from a
larger area. This is particularly advantageous in areas
of lowrainfall.

10. COMPONENTS OF RAIN WATER
HARVESTING
 Catchment area-
 Rain water can be collected from most forms of roofs
 Tiled roofs, or roofs sheetedwith
corrugated mild steel etcare
 preferable, since theyare theeasiest to useand give the
cleanestwater.

11.  Thatched orpalm leafed surfaces are also feasible,
although they are difficult toclean and can often
taint the run-off.
 Asbestos sheeting or lead-painted surfaces should
be avoided.

12. •Gutters and pipes
In a roof top system gutters and pipes are
used tocollectand transport water to the
storagetanks.
These pipesand gutters can be made of PVC or
metal,but PVC is widely used.

13. •Filters
Theyare used to filterout thedebris that
comes with the roof topwaterand prevent
them being added to the storage tank.
-Mesh filters
-First-flushing devices
-sediment dischargetap
Mesh filter and first

14. •Storage facility
Storage tank is the structure where the water is
stored.
This can be varied according tothe
•shape- cylintrical,rectangular,hexangular,square
•Material of construction- rainforced cement
concrete (RCC),Ferro cement,Masonery,Plasticor
metal sheets.
•Position of tank-Aboveground,Partly
underground,fully
underground

15. •Storage tanks in different shapes
and positions

16. •Devices to draw waterout
This includedevices such as hand pumps,
motorized pumps or taps.
Thedevicedepends on the position of the
tank and the use of water.

17. ADVANTAGES OF RAIN
WATER HARVESTING
•Relatively cheap materials can be used for construction of
containers and collecting surfaces
•Construction methods are relatively straight forward
•Low maintenance costs andrequirements
•Environment friendly
•Increase the ground water level andquality.
•Mitigates the effects ofdrought.
•Reduces therunoff
•Reduces the soilerosion
•Helps in reducing water and electricitybills
•Provides a supply of safe water close to homes, schools or
clinics, encourages increased consumption, reduces the
time women and children spend collecting water, reduces
back strain or injuries from carrying heavy water

18. DISADVANTAGES OF RAIN WATER
HARVESTING
•Supplies can be contaminated by
bird/animal droppingson catchment
surfaces and guttering structures unless they
are cleaned/flushed before use
•Poorly constructed water jars/containers can
suffer from algal growth and invasion by
insects, lizards and rodents.They can actas a
breeding ground fordisease vectors if theyare
not properly maintained
•Regular maintenance should beneeded

19. IMPORTANCE OF RAIN WATER
HARVESTING AND FUTURE
•Rain water harvesting plays an
important rolein agriculture
•Useful for urbanareas
•It is important tosave the water for the
future.
•Thus it is important to improverain
water harvesting through technical and
financial prospects.