Rooftop rainwater harvesting system in India.

1. ROOFTOP RAINWATER
HARVESTING
(RRWH)
BY ABHISHEK
ROLL NO. 2106950000005

2. INTRODUCTION :-
• Rooftop Rainwater Harvesting (RRWH) is a technique that collects rainwater from a
building’s roof. The roof acts as a catchment, and the rainwater is stored in tanks or
diverted to an artificial recharge system.
• RRWH is a water conservation technique. It can help recharge groundwater levels and
provide a source of potable water, especially during dry seasons.

3. WHY DO WE NEED RAIN WATER HARVESTING
?
• Water is the reason why life exists on planet
earth, without it life is unimaginable.
• Reports of several global agencies including
united nations indicate that if the current
situation of water does not change and
preventive measures are not taken, then the
world will start to run out of fresh water by 2050.
• Rainwater harvesting is a sustainable process
that helps in preserving rainwater for different
purposes and for future needs as well.

5. COMPONENTS OF ROOFTOP RAINWATER
HARVESTING
1. Catchment
2. Conduits
3. First flush
4. Filters
5. Storage tanks, and
6. Recharge structures

6. 1. CATCHMENTS :-
• The surface that receives the rainfall directly and
transfers water to the system is called catchment
area.
• It can be a paved area such as a building’s terrace
.
• Often usable for water harvesting is a roof made of
reinforced cement concrete ( rcc ) , galvanized iron
or corrugated sheets.

7. 2. CONDUITS :-
• The conduits are pipelines or drains that
bring rainwater to the irrigation system
from the catchment or rooftop area.
• Conduits may be of any type , such as
polyvinyl chloride ( pvc) or galvanised iron
(gi).

8. 3. FIRST-FLUSHING :-
• A first flush device is a valve which ensures that the runoff from the
first rain spell is flushed out and is not entering the system.
• This needs to be achieved , as the first rain spell brings a
comparatively greater volume of air and catchment surface
contaminants.

9. 4. FILTERS :-
• Sand filters have commonly available sand as filter
media. Sand filters are easy to set up and are
inexpensive.
• These filters can be used to treat water to efficiently
reduce turbidity (suspended particles such as silt and
clay), colour, and microorganisms.
• The top layer contains coarse sand followed by a 5-10
mm layer of gravel followed by another 5-25 cm layer of
gravel and boulders in a basic sand filter that can be built
domestically.

10. 5. STORAGE TANKS :-
• There are different options available for the construction of these tanks in terms of form,
height, construction material and tank location and they are: – shape : cylindrical, square
and rectangular.
• Material of construction : Reinforced cement concrete, (rcc), ferro cement, masonry,
plastic (polyethylene) or metal (galvanised iron) sheets are commonly used .
• Position of tank : Depending on space availability these tanks could be constructed
above ground, partly underground or fully underground. Some maintenance measures
like cleaning and disinfection are required to ensure the quality of water stored in the
container .

12. METHODS OF ROOF TOP RAINWATER
HARVESTING
• Storage of direct use.
• Recharging structure.

13. 6. STORAGE OF DIRECT USE :-
• In this method rain water collected from the roof of the building is diverted to a storage
tank.
• The storage tank has to be designed according to the water requirements , rainfall and
catchment availability.
• It is advisable that each tank should have excess water over flow system. Excess water
could be diverted to recharge system.
• Water from storage tank can be used for secondary purposes such as washing and
gardening etc.

15. 7. RECHARGING STRUCTURE :-
• Ground water table can be recharged by various kinds of structures to ensure
percolation of rainwater in the ground instead of draining away from the surface.
Commonly used recharging methods are :-
• 1). Recharging of bore wells.
• 2). Recharging of dug wells.
• 3). Percolation tank.

16. ADVANTAGES OF ROOFTOP RAINWATER
HARVESTING
• Helps in reducing the water bill.
• Decreases the demand for water.
• Promotes both water and energy conservation.
• This technology is relatively simple, easy to install and operate.
• Reduces the need for imported water.
• Improves the quality and quantity of groundwater.

17. • Regular maintenance is required.
• Requires some technical skills for installation.
• Limited and no rainfall can limit the supply of rainwater.
• If not installed correctly , it may attract mosquitoes and other waterborne diseases.
• One of the significant drawbacks of the rainwater harvesting system is storage limits.
DISADVANTAGES OF ROOFTOP RAINWATER
HARVESTING