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Rainwater Harvesting

Presented By-Nitin ChhaperwalClass-XRoll No. 1013

Presented To- Sh. Sunil Khichar Sir

Rain Water Rain Water Harvesting?. Harvesting?. • Rain Water Harvesting RWH- process of collecting,

conveying & storing water from rainfall in an area – for beneficial use.

• Storage – in tanks, reservoirs, underground storage- groundwater

• Hydrological Cycle

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What Is Rainwater Harvesting?

RWH technology consists of simple systems to collect, convey, and store rainwater. Rainwater capture is accomplished primarily from roof-top, surface runoff, and other surfaces.

RWH either captures stored rainwater for direct use (irrigation, production, washing, drinking water, etc.) or is recharged into the local ground water and is call artificial recharge.

In many cases, RWH systems are used in conjunction with Aquifer Storage and Recovery (ASR). ASR is the introduction of RWH collected rainwater to the groundwater / aquifer through various structures in excess of what would naturally infiltrate then recovered for use

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Why Rainwater Harvesting?

Conserve and supplement existing water resources

Available for capture and storage in most global locations

Potentially provide improved quality of water

Supply water at one of the lowest costs possible for a supplemental supply source.

Capturing and directing storm water (run-off) and beneficially use it

Commitment as a corporate citizen - showcasing environmental concerns

Public Mandate (India)

Replenishing local ground water aquifers where lowering of water tables has occured

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Why Not RWH?

Not applicable in all climate conditions over the world

Performance seriously affected by climate fluctuations that sometimes are hard to predict

Increasingly sophisticated RWH systems (ASR) necessarily increases complexities in cost, design, operation, maintenance, size and regulatory permitting

Collected rainwater can be degraded with the inclusion of storm water runoff

Collected water quality might be affected by external factors

Collection systems require monitoring and continuous maintenance and improvement to maintain desired water quality characteristics for water end-use

Certain areas will have high initial capital cost with low ROI

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Condensation

Precipitation

Evaporation

Surface Water

Infiltration

Evapotranspiration

Let’s take a look atThe Water

Cycle

Consumption

Surface Runoff

Groundwater

Sea water intrusion

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Condensation

Precipitation

Surface Water

Groundwater

Consumption

Rainfall Definitions

Intensity – Quantity per time of the rainfall event (mm/hour)

Duration – period of time for the precipitation event

Average Annual and Monthly Precipitation – Average rainfall over one year period and monthly intervals and usually based on 30 or more years of data

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1 Roof2 Screen3 Discharge of water

4 Pre-filter5 Storage tank6 Flow meter7 Storm water discharge

Raw water tank or Aquifer

1

2

34

5

6

7

Rain Water as Source WaterDesign Considerations

Rain Water as Source WaterDesign Considerations

Typical Diagram Recomendation

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Ground Water Recharge

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.

Appropriate Technology

Water conservation and groundwater recharge techniques

Water harvesting cum supplementary irrigation techniques in Jhabua

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Ground catchments systems channel water from a prepared catchment area into storage. Generally they are only considered in areas where rainwater is very scarce and other sources of water are not available. They are more suited to small communities than individual families. If properly designed, ground catchment systems can collect large quantities of rainwater.

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Storage

• Storage devices may be either above or below ground• Different types include

Storage Tanks Water Containers Lagoons or Lined Ponds Infiltration Ponds

Size based on rainfall pattern, demand, budget and area

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Percolation PitTo divert rainwater into an aquifer,

The percolation pit is covered with a perforated concrete slab

The pit is filled with gravel/ pebbles followed by river sand for better percolation.

The top layer of sand must be cleaned and replaced at least once in two years to remove settled silt for improving the percolation

• Roof Rain Water Harvesting

• Land based Rain Water Harvesting

• Watershed based Rain Water harvesting

• For Urban & Industrial Environment –

• Roof & Land based RWH

• Public, Private, Office & Industrial buildings

• Pavements, Lawns, Gardens & other open spaces

RWH – Methodologies RWH – Methodologies

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Recharge Wells

The runoff water from rooftops or other catchments can be channelized into an existing /new well via sand filter to filter turbidity and other pollutants

Abandoned wells can also be used

Cost-effective process, which not only conserves rainwater for immediate use but also helps to enhance the local ground water situation

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•Storage tank – dark materials to exclude light and

algae formation

•Corrosion resistant materials

•Tank in protected shaded area – lower temperature

•For multiple storage tanks – design for frequent

turnover

•Regional wind direction and industrial activity –

Lead, Mercury, other heavy metals

Operational Procedures and Design Considerations

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MANICURED LAWN

POROUS PARKINGGARDEN

GREEN ROOF

GREEN ROOF

OZONATION FILTRATION

BACKUP MUNICIPAL SUPPLY

RAIN WATER HARVESTING FOR OFFICES – Developing a GREEN BUILDING in Nairobi, Kenya

Concept & Design PrinciplesOVERFLOW GROUND WATER REPLENISHING WELLS

RAIN WATER ACCUMULATION IN LIEU OF STORM WATER ATTENUATION POND

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PRINCIPLES OF A GREEN BUILDING - WATER

SYSTEM OF RAIN WATER HARVESTING AND GREY WATER ARE COMBINED TO ACHIEVE THE FOLLOWING:

• 25% OF POTABLE WATER CONSUMPTION REDUCTION

• 100% OF POTABLE WATER PROVIDED BY RAIN

• 50% REDUCTION OF SEWER QUANTITIES

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Water harvesting structures in India

Not new to India

Rainwater storage reservoir at Dholavira (Rann of Kutch) – Harappan civilization (2500-1900 BC)

Centuries old ‘Kul irrigation’ in the Western Himalayan mountainous rain-shadow regions like Spiti valley

Glacier melt is diverted into the head of a ‘kul’ or a diversion channel

These ‘kuls’ channel the water over

many kilometers

They lead into a tank in the village from which water flow is regulated

Inundation channel Bengal Flood plains

River

Kana/ Nadi

Emban

kmen

t

Fields

Fields

Floodwater entered the fields through the inundation canals

The waters brought in rich silt and fish

The fish fed on mosquito larva and helped check malaria in this region.

Khadins of Jaisalmer(harvesting structures for agricultural fields)

Designed by the Paliwal Brahmins of Jaisalmer, in 15th century Similar system also practised in Ur (Iraq), the Negev desert, and in south west Colorado An embankment prevents water from flowing away. Collected water seeps into the soil. This water saturates land, which is then used for growing crops

Johads of Rajasthan(provide water for domestic use) Earthen or masonry rainwater harvesting structure,

for providing water for domestic use to the communities.

Photo by L R Burdak

Photo by Farhad Contractor, taken in Alwar district of Rajasthan

Johads of Rajasthan(provide water for domestic use)

Read about revival of Johads in ‘Reviving India’s water harvesting systems’

Tankas of Bikaner, Barmer, Phalodi - Rajasthan

Note the slope provided for the rainwater (palar pani) to flow into the tanka

Pipes from the rooftop lead rainwater into the tanka catchment

Tankas for storing drinking water Thar desert region of Rajasthan (Barmer, Bikaner, Pallodi)

Unique underground structures of various shapes and sizes to collect rain water for drinking purposes

Sometimes used to store drinking water brought from far off wells in case the rainwater gets exhausted

Constructed in court yards or in front of houses and temples,

Built both for individual households as well as for village communities

Main source of drinking water in these areas

People protect and maintain them

Just before the on-set of the monsoon, the catchment area of the Tanka is cleaned up to remove all possible pollutants

Human activity and grazing of cattle in the area is prohibited

First spell of rain not collected

Tankas of Bikaner, Barmer, Phalodi - Rajasthan

Tankas of Bikaner, Barmer, Phalodi - Rajasthan Provide enough drinking water to tide over the water scarcity during the summer months even though average annual rainfall is as less as 200 mm to 300 mm.

In many cases the stored water lasts for the whole year.

These simple traditional water harvesting structures are useful even during years of below-normal rainfall.

Bamboo drip irrigation in Meghalaya

Bamboo drip irrigation in Meghalaya

200-year-old system

Used by tribal farmers of Khasi and Jaintia hills

Bamboos divert water from perennial springs on hilltops to the lower reaches by gravity

Used to irrigate the betel leaf or black pepper crops

18-20 litres of water entering the bamboo pipe

system per minute gets transported over several

hundred meters and finally gets reduced to 20-80

drops per minute at the site of the plant.

Attempts made to introduce modern pipe systems but farmers prefer to use their indigenous form of irrigation.

Rainwater harvesting today

Collection (Catchment)Flat / sloping roofs

Leaf and grit filter, First flush device

Transportation: Downtake pipes

Storage in tanks

Recharge into open wells / borewells / percolation pits / trenches

Thank You

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