- Rainwater harvesting is the collection and storage of rainwater runoff for reuse on site rather than allowing it to run off. It has been used since ancient times in places like India and Pakistan. - Rainwater can be collected from rooftops or surface runoff and stored in tanks or recharged into groundwater. The stored water can be used for purposes like drinking water, irrigation, and indoor non-potable uses. - A basic rainwater harvesting system has components like a catchment area, gutters and pipes to transport water, filters to treat water, and a storage tank. States like Tamil Nadu and Maharashtra in India have made rainwater harvesting mandatory for buildings.

1. P.E.S.’s Modern College
Of Engineering, Pune
Civil Engineering Department

2. BASIC CIVIL &
ENVIRONMENTAL
ENGINEERING
SEMINAR

3. RAIN WATER HARVESTING
• BY:
• SHRINIVAS KALE
• UMESH SHIRSAT
• ADITYA RAUT
• PANKAJ TUPE
• MAHENDRA SHENDGE

4. Rainwater Harvesting
• Rainwater Harvesting is the accumulation and deposition of rainwater for
reuse on-site, rather than allowing it to run off.
• Rainwater can be collected from rivers or roofs, and in many places the water
collected is redirected to a deep pit (well, shaft or borehole), a reservoir with
percolation, or collected from dew or fog with nets or other tools.
• Its uses include water for gardens, livestock, irrigation, domestic use with
proper treatment, and indoor heating for houses etc.
• The harvested water can also be used as drinking water, longer-term storage
and for other purposes such as groundwater recharge.

5. History
• Around the third century BC, the farming communities in Baluchistan (now
located in Pakistan, Afghanistan and Iran), and Kutch, India, used rainwater
harvesting for agriculture and many uses also.
• In ancient Tamil Nadu , rainwater harvesting was done by Chola kings.
• Rainwater harvesting was done in the Indian states of Madhya Pradesh,
Maharashtra, and Chhattisgarh

7. Methods of Rainwater Harvesting
• Surface runoff harvesting : In urban area rainwater flows away as surface
runoff. This runoff could be caught and used for recharging aquifers by
adopting appropriate methods.
• Roof top rainwater harvesting : It is a system of catching rainwater where
it falls. In rooftop harvesting, the roof becomes the catchments, and the
rainwater is collected from the roof of the house/building.

8. Components Of The Roof Top Rainwater
Harvesting
• Catchment : The surface that receives rainfall directly is the catchment of
rainwater harvesting system. The catchment is the area, which actually
contributes rainwater to the harvesting system.
• Transportation : Rainwater from rooftop should be carried through down
take water pipes or drains to storage/harvesting system. Water from sloping
roofs could be caught through gutters and down take pipe. At terraces,
mouth of the each drain should have wire mesh to restrict floating material.

9. • First Flush : First flush is a device used to flush off the water received in first
shower. The first shower of rains needs to be flushed-off to avoid
contaminating storable/rechargeable water by the probable contaminants of
the atmosphere and the catchment roof. It will also help in cleaning of silt and
other material deposited on roof during dry seasons Provisions of first rain
separator should be made at outlet of each drainpipe.
• Filter : There is always some skepticism regarding Roof Top Rainwater
harvesting since doubts are raised that rainwater may contaminate groundwater.
Filters are used fro treatment of water to effectively remove turbidity, color and
microorganisms. After first flushing of rainfall, water should pass through
filters. A gravel, sand and ‘netlon’ mesh filter is designed and placed on top of
the storage tank.

10. Quality
• The concentration of contaminants is reduced significantly by diverting the
initial flow of run-off water to waste.
• Improved water quality can also be obtained by using a floating draw-off
mechanism (rather than from the base of the tank) and by using a series of
tanks, with draw from the last in series.
• Supplying rainwater that has gone through preliminary filtration measures for
non-potable water uses, such as toilet flushing, irrigation, and laundry, may
be a significant part of a sustainable water management strategy.

12. System Setup
• Rainwater harvesting systems can range in complexity, from systems that can
be installed with minimal skills, to automated systems that require advanced
setup and installation.
• Specifically, the rainfall capturing area such as a building roof must be large
enough to maintain adequate flow.
• The water storage tank size should be large enough to contain the captured
water.

13. Advantage
• Easy to Maintain
• Reducing Water Bills
• Suitable for Irrigation
• Reduces Floods and Soil Erosion
• Reduces Demand on Ground Water

14. Disadvantages
• Unpredictable Rainfall
• Initial High Cost
• Regular Maintenance
• Regular Maintenance

15. New Approaches
• Instead of using the roof for catchment, the Rain Saucer, which looks like an
upside down umbrella, collects rain straight from the sky.
• This decreases the potential for contamination and makes potable water for
developing countries a potential application.
• Other applications of this free standing rainwater collection approach are
sustainable gardening and small plot farming

16. Current Use
• India
• Tamil Nadu: Tamil Nadu was the first state to make Rainwater Harvesting
compulsory for every building to avoid groundwater depletion.
• Maharashtra: At present, in Pune, rainwater harvesting is compulsory for any
new housing society to be registered
• The Mumbai city council is planning to make rainwater harvesting
mandatory for large societies.

18. THANK YOU