The document discusses rainwater harvesting (RWH), emphasizing its importance in water conservation, especially given the global water scarcity issues. It outlines the objectives, methods, advantages, and disadvantages of RWH systems, particularly in India, highlighting successful cases and government initiatives. Key applications of RWH include domestic use, agriculture, and urban planning, with an emphasis on its role in sustainable development and climate resilience.

1. Rain water
Harvesting
Swagatika Sahoo
PG Scholar

2. Table of contents
o What is Rainwater harvesting ?
o Need for rainwater harvesting
o Objectives
o Methods of Rainwater Harvesting
o Ground water recharge techniques
o Advantages & Disadvantages of RWH system
o Applications
o Rain water harvesting in India
o Conclusion
o References 2

3. 3
What is Rainwater
harvesting ?
o The harvesting of rain water simply
involves the collection of water from
surfaces on which rain falls, and
subsequently storing this water for later
use. Normally water is collected from the
roofs of buildings and stored in rainwater
tanks.
o It is the accumulation and deposition of
rainwater for reuse on site.

4. 4
Acc. to WHO around the world
roughly 2.1 billion people lack reliable
access to clean drinking water
The global NEED for water will EXCEED the
global SUPPLY of water 40% by the year
2030.
Everyday GROUNDWATER provides
drinking water for over 158 MILLION
PEOPLE.
1 litre of waste
water pollutes 8
litres of fresh
water.

5. Need for Rainwater Harvesting
● Due to ever increasing population, surface water is not enough to meet all the demands and the
dependance automatically goes to ground water that drastically leading to constant depletion of ground
water level causing the wells and tube wells to dry up.
5
According to NOAA (National Oceanic and
Atmospheric Administration), nearly 30% of our
freshwater consumption accounts from groundwater
sources.
● To enhance availability of ground water at specific place and time and utilize rain water for sustainable
development.
● Regional Variations in water availability
● Responsibilities towards protecting Nature
● Quality of water supplies
● To increase infiltration of rain water in the subsoil this has decreased drastically in urban areas due to
paving of open area.
● To increase agriculture production.
Out of 8760 hours in a year, most of the rain in India falls in just 100 hours.

6. Objectives of RWH
• Increase availability of water during dry season
• Substitute ground water
• Prevent overuse of Aquifers
• Reduce flood risk and soil erosion
• Save money on water bills and improve living conditions
6

7. 7
Methods for Rainwater Harvesting
● Rooftop rainwater Harvesting
There are broadly 2 ways of harvesting rain water.
● Surface (ground) runoff Harvesting
o Rainwater flows away as surface runoff.
This runoff could be caught and used for
irrigation and recharging aquifers by
adopting appropriate methods.
o It is less expensive.
o 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.
o It can either be stored in a tank or diverted to
artificial recharge system.
Driveway
Source. Vikaspedia.in

8. 8
Rooftop rainwater
harvesting system
● Components
1. Catchment area
2. Conveyance system
3. Storage tank
4. Recharge structure
• Gutter and down take pipe
• First flush and filter
• Delivery system
3 Discharge of waste 6 Flow meter
7 water discharge
Source. Theconstructor.org

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Catchment
● Any surface or the paved areas can be treated as catchment. Even the footpaths and roads can act as
the catchment, as these areas too receive the direct rainfall.
● Rooftops are the best among them because of the large coefficient of runoff and less chances of
contamination of water.
● Tiles and Metal roofs are even better as concrete absorb some water .
● The amount of water harvested depends on the quantity of rainfall, and the size of the surface and the
slope of the catchment area.
Rain Water harvesting potential = Amount of Rainfall x area of catchment x Runoff coefficient

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Conveyance
• Conveyance system basically includes rain gutters and down pipes which collects the rain water from
catchment to the storage tank.
• These rain gutters are usually built during the time of construction. They need to be designed appropriately
as to avoid the loss of water during the conveyance process.
Fig. gutters and down pipes
Source. Theconstructor.org

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● Roof washers - a device that diverts the "first flush" of rain before it enters the storage tank. Most
rainwater suppliers recommend that the "first flush" of water is diverted to an outside area of
the storage system, since the catchment surface may accumulate bird droppings, debris and other
pollution.
● Leaf screens - To prevent the entry of leaves and other debris in the system, the coarse mesh
should be provided at the mouth of inflow pipe.
Source; vanislewater.com
thegreenmanproject.com
Fig. first flush device Fig. leafscreens

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● Delivery systems - Piping systems that convey the stored rainwater till the point of end-use.This
include devices such as hand pumps, motorized pumps or taps.
● The device depends on the position of the tank and the use of water.
fig. Devices to draw water out i.e.taps (left) handpumps (right)
Source; solarhaven.org

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• Purification/treatment system - needed for making the water safe for human consumption,
and meeting certification requirements.
• A sand filter or water filter used to make the water usable for daily activities and RO filter is
used to make the water potable.
Fig. sand filter Fig. charcoal water filter
IS 10500 (2012): Drinking water

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Storage
● The storage tank can be cylindrical, rectangular or square in shape. The material of construction can be
RCC, ferrocement, masonry, PVC or metal sheets.
● Depending upon the availability of space, the storage tank can be above ground, partially underground or
fully underground.
● The storage system should be properly sealed and does nor leak. Chlorine is used from time to time to
keep the water clean.
● The design of storage tank is dependent on many factors
a) Number of persons in the household
b) Average annual rainfall
c) Rainfall pattern
d) Type and size of catchment
Fig. Storage tanks in different shapes
Source; pinterest

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Fig. Storage tanks in different positions

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Following precautions should be taken to ensure quality of water:
● Roof over which water falls, should be cleaned before rain fall.
● The suitable type of first flushing device to be installed and initial 10 to 15 minutes of runoff should
be diverted.
● The water collected from roof top only, should be stored in storage tank for direct use.
● The runoff from surface/ground should be preferably be used for recharging ground water aquifers
after proper filtration.
● The rain water collected from roof top should pass through suitable type of filter and only then it
should be stored in storage tank / used for recharging ground water aquifers.
The rain water is one of purest form of water and does not contain suspended / dissolved impurities.
However when this water is collected through rain water harvesting, it gets contaminated because of
contact with roof surface/ground and some of the impurities get mixed in it. These impurities are
required to be removed before collecting the harvested rain water in storage tank or diverting it or
recharging of ground water aquifers.
Quality issues

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Recharging subsurface aquifers
● Under natural conditions it may take days to centuries to recharge ground water by rain water. As
we need to replenish the pumped water, Artificial Recharge of Ground water is required at some
locations.
● It is estimated that only 10 to 25% of rain water is utilized to charge ground water but artificially with
rain water harvesting, it can be charged upto 50%. (source: para 2.6.3 of manual of rain water
harvesting & conservation - Govt of India)

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1. Through recharge pit
● This method is suitable where permeable strata
is available at shallow depth.
● Recharge pit of any shape is constructed generally
1-2 m wide and 2-3 m deep. The pit is filled with
boulders, gravel and sand for filtration of rain
water.
Source; clearwaterdynamics.com
Fig. recharge pit

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2. Through recharge trench
● Trenches 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.
Fig. Ground water recharge through recharge trench
Source: frontdesk.co.in

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3. Through existing dugwells
● Existing dug wells may be utilised as recharge
structure and water should pass through filter
media before putting into dug well.
Fig. recharge through wells

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4. Through recharge shaft
● This method is suitable where shallow aquifer is located below clayey surface.
● Recharge shaft of diameter 0.5-3 m and 10-15 m deep is excavated mechanically. The shaft should end in
more permeable strata below the top impermeable strata.
● The shaft should be filled with boulders, gravel and sand for filtration of recharge water. Top sand layer
should be cleaned periodically.
● By constructing recharge shaft in tanks, surplus water can be recharged to ground water. The top of shaft is
kept above the tank bed level preferably at half of full supply level.
Fig. Aquifer recharge through recharge shafts

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5. Through recharge trench with bore
● This method is used where sub-soil is
impervious and large quantity of roof water/
surface run off is available.
● In this, trench is made 1.5-3 m wide and 10-30 m
length depending upon water availability. Wells of
150-300 mm dia. and 3-5 m deep (below pervious
layer) are constructed in the trench.
● Numbers of wells to be dug are decided in
accordance to water availability and rate of
ingression.
● Trench is filled with filtration media .
● A suitable silt chamber is also inserted with
grating for water diverting arrangements.

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6. Spreading techniques
• When permeable strata starts from top then this technique is used.
• Spread the water in streams/Nalas by making check dams, nala bunds, gabion structures or a
percolation pond may be constructed.
Source; aamjanata.com
fig. check dams fig. Percolation ponds fig. gabions
Gettyimages.ae

24. 24
Fig. Pavers with holes for ground water
recharge

25. 25
Advantages of rain water Harvesting
● Provide self-sufficiency to water supply.
● Reduces the cost for pumping of ground water.
● Provides the high quality water, soft and low in minerals.
● Improves the quality of ground water through dilution when recharged.
● Reduce soil erosion & flooding in urban areas.
● The roof top water harvesting is less expensive & easy to construct, optimum and maintain.
● In desert , RWH only reliefs.
● No land is wasted for storage purpose and no population displacement is involved.
● Ground water is not directly exposed to evaporation and pollution.
● Effects rise in ground water levels.
● Mitigates effects of drought.

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Disadvantages
● In terms of complex constructions, there is a requirement for high costs, trained
professionals. Maintenance costs may add to the monetary burden.
● If not maintained properly then it can cause various problems in terms of algal or
bacterial growth.
● Tanks if not constructed properly might result in leakages and metal tanks may
also lead to problems such as corrosion harming the water quality.
● All these factors might prove harmful and result in various kinds of health issues.
● The system is very much rainfall dependent and hence if there are problems with
the rainfall in the area, it may not be very effective.

27. Completeness
Both rooftop and driveway runoff water must be harvested
Apportioning of water
04
02
01
03
Volume of water likely to flow through and the nature of
the soil in the area should be considered
Proper design
Design should incorporate features
allowing for periodic maintenance of the
structure
Characteristicsof a good RWH System
To avoid overload of any one system, leading to
overflow and loss
Maintainability

28. 28
Applications of RWH
o Rainwater harvesting in urban areas reduces the impact of runoff and flooding.
o The combination of urban ‘green’ rooftops with rainwater catchments have been found to reduce
building temperatures by more than 1.3 degrees Celsius.
o Rainwater harvesting in conjunction with urban agriculture would be a viable way to help meet
the United Nations Sustainable Development Goals for cleaner and sustainable cities, health and
wellbeing, and food and water security.
o Many countries, with arid environments, use rainwater harvesting as a cheap and reliable source
of clean water. To enhance irrigation in arid environments, ridges of soil are constructed to trap
and prevent rainwater from running down hills and slopes. Even in periods of low rainfall, enough
water is collected for crops to grow.
1. Agriculture
2. Domestic use

29. 29
3. Industry
o Frankfurt Airport has the biggest rainwater
harvesting system in Germany. The system helps
save approximately 1 million cubic meters of water
per year.
o This system collects water from the roofs of the new
terminal which has an area of 26,800 square meters.
The water is collected in the basement of the airport
in six tanks with a storage capacity of 100 cubic
meters. The water is mainly used for toilet flushing,
watering plants and cleaning the air conditioning
system.
Source; Wikipedia.org
AusAID has installed rainwater harvesting systems
in Kiribati to ensure cleaner, safer drinking water,
reduce water leakages and waste in existing
systems, and help the Government of Kiribati
protect water reserves. © AusAID

30. 30

31. 31
5. Green building
● A ‘green’ building is a structure that, in its design, construction or operation, reduces or eliminates
negative impacts, and can generate positive impacts, on our health and natural environment.
● Green buildings preserve precious natural resources and improve our living standard. There are a
number of features which included to make a building ‘green’.
o Efficiently using energy, water, and other resources
o Protecting occupant health and improving employee
productivity
o Reducing waste, pollution and environmental
degradation
common objective of green buildings
Fig. green roof with rain water harvesting system

32. Rain Water Harvesting
in India

33. Rajendra Singh
● Rajendra Singh, also known as the ‘Waterman of India’, is a renowned water conservationist
and environmentalist from Rajasthan.
● He used an ancient method of conserving rainwater called ‘Johad’
● Johads are large crescent-shaped earthen check dams made of rocks and earth.
● In 1975, Rajendra Singh founded an NGO Tarun Bharat Sangh.
● starting from a single village in 1985, over the years TBS helped build over 8,600 johads and
other water conservation structures to collect rainwater for the dry seasons, has brought water
back to over 1,000 villages and revived five rivers in Rajasthan, Arvari, Ruparel, Sarsa, Bhagani
and Jahajwali.
● In recognition of his work, Rajendra Singh was awarded the Ramon Magsaysay Award for
Community Leadership in 2001 and Stockholm Water Prize in 2015.

34. A. R. Shivakumar
● A.R. Shivakumar, also known as the ‘Rain Man’, built an eco-friendly home way back in 1995.
● Being a senior scientist at the Karnataka State Council of Science and Technology, he studied the rainfall
pattern in Bengaluru before constructing his house and found out the city receives an average rainfall of
around 1000mm every year.
● Shivakumar’s house ‘Sourabha’ has a rainwater harvesting system along with a solar energy plant to
power the house, a solid waste management system and a natural cooling system.
● The rainwater harvesting system installed in Shivakumar’s house has a storage capacity of 45,000 liters,
which suffices the drinking water and other water needs of his family
Sourabha doesn’t have a water connection and
Shivakumar hasn’t paid anything to the Bangalore
Water Supply & Sewerage Board since constructing
his eco-friendly home!

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1. TAMIL NADU’S SUCCESS
● While the rest of the country is busy devising methods to conserve water for the forthcoming months,
Tamil Nadu seems to have a head start with its successful rain water harvesting scheme.
● In 2016, Tamil Nadu witnessed the worst drought in the last 140 years. The drought triggered a series
of measures to prevent such a crisis.
● The district collectors were directed to analyse historical data to identify blocks and villages that face
drinking water crisis in the event of rainfall deficit.
● Water bodies and supply channels were cleaned. Small check dams were set up to store water near
streams and borewells with drinking water. Defunct borewells were converted into water recharging
ones through rainwater harvesting.
● Tamil Nadu has been a trendsetter in rain water harvesting, making it mandatory for all buildings as
far back as 2003.
● Today, according to the State government website, out of the 23.92 lakh buildings in town Panchayats
(government, residential, commercial and industrial), 22.94 lakh have rainwater harvesting facilities.

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India’s effort on water conservation
● Many efforts are there by the central and state government on Rain water Harvesting and Artificial
recharge.
● The largest activity is under Mahatma Gandhi National Rural Employment Guarantee Act,2005
(MGNREGA)
● Roof top rainwater harvesting has become mandatory in many urban areas like Chennai , Hyderabad
etc. Though strict implementation is an issue.
● RWH and aquifer recharge remained disseminated small structures. Many a times community driven.
www.thehindubusinessline.com

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22 march 2021, on World Water Day, Prime Minister
Narendra Modi launched “Jal Shakti Abhiyan : Catch
the Rain” (JSA:CTR) campaign of National Water
Mission (NWM) .it will run from 22 March 2021 to 30
November, 2021 in the pre-monsoon and monsoon
periods of 2021, covering both urban and rural areas of
all the districts in the country.
The campaign aims at encouraging the states and stake-
holders to take steps towards rainwater harvesting by
creating appropriate Rain Water Harvesting Structures
(RWHS) suitable to the climatic conditions and sub-soil
strata before the monsoon.
To facilitate the activities, states have been requested to
open ‘Raincenters’ in each district - in
Collectorates/Municipalities or Gram Panchayats offices.
these ‘Raincenters’ will have a dedicated mobile phone
number and will be manned by an engineer or a person
well trained in RWHS. The center acts as a technical
guidance center to all in the district as to how to catch the
rain, as it falls, where it falls.

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Conclusion
Harvesting and collection of rainwater is an adequate strategy that can be used to
address the problem of water crisis globally. The use of a rainwater harvesting system
provides excellent merits for every community. This simple water conservation method
can be a boost to an incredible solution in areas where there is enough rainfall but not
enough supply of groundwater. It will not only provide the most sustainable and efficient
means of water management but also unlock the vista of several other economic
activities leading to the Empowerment of people at the grass-root level.
For this, the Government should come out with an appropriate incentive structure and
logistic assistance to make it a real success.

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References
o www.Wikipedia.org/rainwater harvesting
o Search | www.gardenorganic.org.uk
o Pdf. WATER CONSERVATION & RAINWATER HARVESTING FOR BRIHANMUMBAI Released ;-
15th Oct. 2003
o https://sswm.info/sites/default/files/reference_attachments/IRICEN 2… · PDF file
o Frequently Asked Questions (FAQs) - Rainwater Harvesting (RWH) | India Water Portal
o Rainwater Harvesting Pro Directory - Find Rainwater Harvesting Pros - rainwaterharvesting.com
o Rainwater harvesting Manual. Indian railways institute of civil engineering ,Pune august 2006
o www.aboutrainwaterharvesting.com

41. 41
o Green Building with Rain Water Harvesting Approach Latif Shaikh B-Tech Civil Engineering,
Department of Technology, Shivaji University, Kolhapur, India, International Journal of Science and
Research (IJSR) ISSN: 2319-7064
o Government Initiatives | Department of Water Resources, RD & GR | Government of India
(mowr.gov.in)
o Bore well Recharge RWH | Sankalpa Rural Development Society (srdsindia.org)
o Rain water harvesting techniques to augment ground water — Vikaspedia
o SELECT CASE STUDIES RAIN WATER HARVESTING and ARTIFICIAL RECHARGE. Central
Ground Water Board Ministry of Water Resources New Delhi May 2011
o Methods of Rainwater Harvesting -Components, Transport and Storage (theconstructor.org)
o www.slideshare.net/rainwaterharvesting

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Thanks!