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Methods of Water Conservation
by
Prof. A. Balasubramanian
Dept. of Studies in Earth Science
University of Mysore
Mysore, India

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Introduction:
Water is a very important resource in our life.
Water is becoming scarce due to increase in Population,
industries and agricultural activities and due to poor rainfall.
A report of 2009 suggested that by 2030, in some developing
regions of the world, water demand will exceed supply by
50%.
Water plays an important role in the world economy, as it
functions as a solvent for a wide variety of chemical
substances and facilitates industrial cooling and
transportation.

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Goals of Water Conservation
1) Sustainability: To ensure availability for future
generations, the withdrawal of fresh water from an ecosystem
should not exceed its natural replacement rate.
2) Energy conservation: Water pumping, delivery, and
wastewater treatment facilities consume a significant amount
of energy. In some regions of the world over 15% of total
electricity consumption is devoted to water management.
3) Habitat conservation: Minimizing human water use helps
to preserve fresh water habitats for local wildlife and
migrating water flow, as well as reducing the need to build
new dams and other water diversion infrastructure.

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Water harvesting and conservation
Water conservation refers to reducing the usage of water and
recycling of waste water for different purposes like domestic
usage, industries, agriculture etc.
Methods of Water Conservation:
1. Protection of Water from Pollution;
2. Redistribution of Water
3. Rational Use of Groundwater
4. Renovation of Traditional Water Sources
5. Use of Modern Irrigation Methods

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6. Increasing Forest Cover
7. Change in Crop Pattern
8. Flood Management
9. Conserving Water in Industries
10. Conservation of water by Municipal authorities
11. Use rainwater effectively
12. Make effective use of soil water reserves
13. Take measures to avoid run off
14. Avoid wasting water through evaporation
15. Reduce water losses through drainage
16. Plan your irrigation
17. Contour Farming& Contour Ploughing

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Contour Furrows
Bench Terraces

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Grass Strips
Stone Lines

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Retention Ditches
Planting Pits

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Earth Basins
Semi-Circular Bunds

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Cover Crops/Green Manures
Mulching

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Drip Irrigation
Conservation Tillage

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Water Harvesting from External Catchment
Roof Top Harvesting

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Rainwater Harvesting
Rainwater Harvesting is an effective method and a
simple method of collecting water for future usage. Rainwater
harvesting is the process of collecting, filtering, storing and
using rainwater for irrigation and for various other purposes.
Rainwater is collected when it falls on the earth, stored and
utilized for various purposes. It can be purified to make it into
a drinking water facility in some islands and dry land regions.
Rainwater harvesting (RWH) is a simple method by which rainfall is
collected for future usage. The collected rainwater may be
stored, utilised in different ways or directly used for recharge
purposes.

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Benefits of Rainwater Harvesting
Rainwater harvesting has many benefits. The major benefit is
that it is a sustainable water management practice. It can be
implemented by every citizen at various levels. It is a
socially acceptable practice and promotes environmentally
responsible future.
The rainwater that falls on any roof and property is
essentially free. All it needs is to adopt a method to harvest
it and store it in a tank or cistern for future use.
Rainwater harvesting helps to reduce the peak demand of
water expected during summer period, by saving treated
water for more important water uses.

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While rainwater can be a perfect primary water source for
many uses and situations, it is would be a good backup water
supply for emergency situations.
The Environmental Benefits
Rainwater harvesting can reduce storm-water runoff and
wastage from any land. The reduction in runoff volume can
reduce the level of contamination of surface water resources
with pesticides, solid wastes, municipal effluents, sediments,
metals, and fertilizers.
By reducing the storm-water runoff, rainwater harvesting can
reduce the flow volume and velocity in local streams, and
rivers. This also help to avoid the potential for erosion along
river beds.

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Rainwater harvesting systems can be an excellent source of
water for growing plants and carry out landscape irrigation.
The Economic Benefits
Collecting and using rainwater, in place of municipal water
supply, reduces the water bill to some extent. This also
reduces the water service cost to a municipality, for their
people.
Rainwater harvesting can reduce water demand from
municipalities. It helps to provide potable water at a lower
cost. Designing and installing rainwater collection systems
can provide sustainable jobs for people and help to earn more.

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The rainwater harvesting industry can become a leading
employer in the green infrastructure movement. Rainwater
stored onsite in a rainwater harvesting system can avoid
increasing forest fires.
Insurance companies can offer better discounts for those who
implement better water management practices.
Miscellaneous Benefits
Rainwater doesn’t have the any chemicals in it. Rainwater
can be used for irrigation. It is a suitable potable water
source. Rainwater harvesting can provide an independent
water source in areas where other water sources are not
available.

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In some places where the water quality is poor, we may use
rainwater, safely.
Good rainwater provides many advantages.
Rainwater harvesting is the key to the future water
conservation gains.
Rainwater harvesting is a vital resource for the future of
sustainable water resources. Reduce demand on Ground
Water.

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Rainwater harvesting is part of a sustainable water supply strategy
for local communities.
Rainwater for Non-drinking Purposes:
Rainwater can be used for several non-drinking purposes like flushing
toilets, washing clothes, watering the garden, washing cars etc. It is a
unhealthy practice to use pure drinking water some other purposes other
than drinking.
Disadvantages of Rainwater Harvesting
Rainfall is unpredictable. There is an Initial Cost for
establishment.
Rainwater harvesting systems require regular maintenance.

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There are limitations in storage tank capacities.
Techniques of Rainwater Harvesting
Rooftop rainwater harvesting (RTRWH) is the most common
technique of rainwater harvesting (RWH) for domestic
consumption. In urban and rural areas, this is most often
practiced method at a small-scale. It is a simple, low-cost
technique that requires minimum specific expertise or
knowledge.

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Rainwater is collected from the roof top and transported with
gutters in to a storage reservoir, where it provides water at the
point of consumption or can be used for recharging a well or
the aquifer.
Collected rainwater can be the best supplement to other water
sources when they become scarce or are of low quality like
brackish water, saline groundwater or polluted surface water,
in the rainy season.
The technology is flexible and adaptable to a very wide
variety of geographic and geomorphic conditions. It is used in
the developed and the developing societies.

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Roof Top Rain Water Harvesting
Basic design principles
Each rainwater harvesting system consists of at least the
following components:
 A catchment area in the roof surface to collect rainwater.
 A delivery channel (gutters) to transport the water from the
roof or collection surface to the storage reservoir.
 Storage tanks or reservoirs to store the water until it is used.
 An extraction device (depending on the location of the tank).

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(Three basic components of a rainwater harvesting system. Source: HATUM & WORM (2006)).

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Surface tank madde out of ferro‐cemment for the storaage of collected ra
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ainwater. Source: DOLMAN & LUNDDQUIST (2008))

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Factors to be considered
 Type and size of catchment area
 Local rainfall data and weather patterns
 Length of the drought period
 Alternative water sources
 Cost of the rainwater harvesting system.
 When rainwater harvesting is mainly considered for
irrigation, several factors should be taken into
consideration. These include: Rainfall amounts,
intensities, and evapo-transpiration rates. Soil infiltration
rate, water holding capacity, fertility and depth of soil .
 Crop characteristics such as water requirement and length
of growing period .

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 Hydrogeology of the site .
The Basic Calculation
Roof top flat area:
4m by 5m = 20 Sq.m
total annual total annual rainfall in mm = 500 mm
efficiency factor / runoff coefficient = 0.9
Annual water supply in liters = 20 x 500 x 0.9 = 9000 liters

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Rainwater Collection
Calculation Formulas and Equations
Roof Area (ft2) X Precipitation Amount (in) X 0.623 =
Amount Collected (gallons)
How to choose the size of the storage tank:
A house with a roof area of 9.00 x 6.50 m is to be furnished
with catchment and storage facilities. The mean annual
rainfall is 450 mm.
Calculation of rainwater:
9.00 x 6.50 x 450 x 0.9 = 23895 litres

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Tamil Nadu:
Tamil Nadu was the first state to make rainwater harvesting
compulsory for every building to avoid groundwater
depletion. The scheme was launched in 2001 and has been
implemented in all rural areas of Tamil Nadu.
Karnataka -World’s largest rainwater harvesting project:
The World’s largest rainwater harvesting project was carried
out in Karnataka.
Rainwater harvesting in rural Karnataka’ funded by Rural
Development and Panchayat Raj Department (RDPR),
Government of Karnataka is probably the largest rainwater

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harvesting project in the world. All the schools of Karnataka
were carefully studied for the water availability, quality
(fluoride contamination) and proximity to the secondary
water source.
Almost 23,683 schools were identified in the first phase to
provide drinking water through rooftop rainwater harvesting
systems.
Steps taken by the Central Government to promote rain water
harvesting in the country are as follows:
1. Central Ground Water Board (CGWB). Govt of India,
has prepared a conceptual document titled “Master Plan for
Artificial Recharge to Ground Water – 2013.

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2. The National Water Policy (2012) formulated by Ministry
of Water Resources, RD & GR, inter-alia, advocates
conservation, promotion and protection of water and
highlights the need for augmenting the availability of water
through rain water harvesting, direct use of rainfall and other
management measures.
3. CGWA( Water Authority) has issued advisories to States
and UTs to take measures to promote/adopt artificial recharge
to ground water/rainwater harvesting. 30 States/UTs have
made rainwater harvesting mandatory by enacting laws or by
formulating rules & regulations or by including provisions in
building bye-laws or through suitable Government Orders.

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4. CGWB has taken up Aquifer Mapping and Management
programme (NAQUIM) during XII Plan, under the scheme of
Ground Water Management and Regulation.
5. Model Building Bye Laws, 2016 circulated by Ministry of
Urban Development include the provision of Rainwater
Harvesting. As per Model Building Bye Laws, water
harvesting through storing of water runoff including rainwater
in all new buildings on plots of 100 sq.m and above will be
mandatory.
6. The Ministry of Rural Development in consultation and
agreement with the Ministry of Water Resources, RD & GR
and the Ministry of Agriculture & Farmers’ Welfare has
developed an actionable framework for Natural Resources

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Management (NRM), titled “Mission Water Conservation” to
ensure gainful utilization of funds.
Types of common works undertaken under these
programmes/schemes are water conservation and
management, water harvesting, soil and moisture
conservation, groundwater recharge, flood protection, land
development, Command Area Development & Watershed
Management.
The government of India is working on a master plan
envisaging construction of about 23 lakh artificial recharge
and rainwater harvesting structure in rural areas and 88 lakh
in urban areas, as informed in the Lok Sabha, already.

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Conclusion:
In many cases, groundwater or surface water may be
unavailable for drinking water. The groundwater level may be
too deep, groundwater may be contaminated with minerals
and chemicals such as arsenic or salt, surface water may be
contaminated with faeces or chemicals. In these cases,
rainwater harvesting can be an effective and low-cost
solution.