rainwater harvesting

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Rainwater Harvesting

2. Rain Water Harvesting?.Rain Water 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 at
The 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 Roof
2 Screen
3 Discharge of water
4 Pre-filter
5 Storage tank
6 Flow meter
7 Storm water discharge
Raw water
tank or
Aquifer
1
2
3
4
5
6
7
Rain Water as Source Water
Design 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.

10. 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 Pit
To 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

14. • 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 – MethodologiesRWH – 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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Quality Issues
Roofs contain: bird droppings, atmospheric dust, industrial and
urban air pollution

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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 PARKING
GARDEN
GREEN ROOF
GREEN ROOF
OZONATION
FILTRATION
BACKUP MUNICIPAL SUPPLY
RAIN WATERHARVESTING FOROFFICES – Developing a GREEN BUILDING in
Nairobi, Kenya
Co nce pt & De sig n Principle s
OVERFLOW
GROUND WATER
REPLENISHING
WELLS
RAIN WATERACCUMULATION IN LIEU OF STORMWATERATTENUATION 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