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8/9/2019 Microsoft Power Point - Rain Water Harvesting [16 Nov 2008]
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BACKGROUND
OF THE TOTAL WATER AVAILABLE 94% IS OCEAN WATER, &
ONLY 2% IS FRESH WATER & BALANCE IN OTHER FORMS.
BUT DUE TO UNPLANNED, WASTEFUL & BLIND USE OF THISPRECIOUS GIFT OF NATURE, THE DAY IS NOT FAR AWAY
WHEN ONE SHALL HAVE TO STARVE FOR WATER.
SO RAIN WATER HARVESTING IS NEED OF THE HOUR DUE TODECREASING TREND OF GROUND WATER
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Water everywhere starts as Rain
Rain is the source of all
water in the world. 98%
of the worlds supply of
water is salt water in the
oceans. 1% of pure wateris in the arctic glaciers.
The last 1% goes
through the water cycle.
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HYDROLOGIC CYCLE
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T E R M I N O L O G Y
Precipitation - it denotes all forms of water that reach earth from theatmosphere as rainfall, snowfall, hail etc
Depression storage - part of precipitation used for filling smalldepressions in the ground
Infiltration - the portion of precipitation which percolates into the ground
Surface runoff - a large portion of precipitation left after infiltration flowsover the ground into the streams
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WHAT IS RAIN WATER HARVESTING ?
The principle of collecting and usingprecipitation from a catchments
surface.
Rainwater harvesting is the capture,diversion, and storage of rainwaterfor later use
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BASICS
OF
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BUYING WATER WHILE IT IS RAINING
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GET FEW BUCKETS OF ROOF WATER
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POUR SOME EXCESS INTO THE SUMP
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CONNECT A HOSE AND DIVERT
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DIVERT THE ENTIRE ROOF WATER
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ADD A FILTER
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Roof top rain water is collected
using a PVC pipe
Filtered using sand and bricks
Underground pipe takes water to
sump for immediate usage.
Excess water from the sump is
taken to the well.
Water from the well recharges the
underground
Take water from the well (later)
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SIMPLEST WAY OF RAINWATER HARVESTING
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NECESSITY OF RAIN WATER HARVESTING
TO ARREST THE DECLINE IN GROUND WATER LEVELS.
TO OVERCOME THE INADEQUACY OF SURFACE WATER
TO MEET OUR DEMANDS.
TO ENHANCE AVAILIBILITY OF GROUND WATER AT
SPECIFIC PLACES & TIME & UTILISE RAIN WATER FOR
SUSTAINABLE DEVELOPMENT
TO INCREASE INFILTRATION OF RAIN WATER IN THE
SUB-SOIL WHICH HAS DECREASED DRASTICALLY
PARTICULARLY IN URBAN AREAS.
TO HARNESS GOOD QUALITY WATER RESOURCE NOW
BEING WASTED
TO AUGMENT THE EXPENSIVE PIPED WATER SUPPLY
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BENEFITS
Save expenditure on water
Inexpensive and simple technology
Aids ecological conservation
Prevent groundwater depletion
Reduces demand on municipal water supply
Makes efficient use of a valuable resource
Reduces flooding, erosion, and contamination of surface
water
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BASIC TYPES
ROOF TOP RAIN WATER HARVESTING &STORAGE IN TANKS.
ROOF TOP RAIN WATER HARVESTING &
RECHARGING OF SUBSURFACE AQUIFER.
SURFACE RUN-OFF HARVESTING &
RECHARGING OF SUBSURFACE AQUIFER
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How Rainwater
Harvesting Works
A rainwater harvesting system consists of
The supply rainwater
The demand The collection system
Simple and complex systems
Simple distribute rainwater immediately
Complex store some or all of rainwater for later
use
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Supply: Rainfall
Supply comes in the form of runoff, rainwaterthat flows off a surface.
If the surface is impermeable, runoff occurs
immediately. Pavement
Concrete
Roofs If the surface is permeable, runoff occurs
when the surface is saturated.
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Demand: Water Requirements
The amount of water needed is determined
by Domestic Water Demand
Industrial Water Demand
Institutional & Commercial Water Demand
Demand for Public Uses
Fire Demand Water Requirement to Compensate Losses
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Simple Rainwater
Harvesting Systems
A simple water harvesting system consists of
Catchment
Distribution System
Landscape Holding Area
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Complex Rainwater
Harvesting Systems
A complex rainwater harvesting systemconsists of catchments, a conveyancesystem, storage, and a distribution system.
Catchments Conveyance Systems
Storage
Distribution System
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Complex Rainwater
Harvesting Systems
Catchments
The yield that a catchment provides depends on itssize and surface texture.
Surface textures include:
High yield concrete, asphalt, and smooth roofing
material Medium yield bare soil; compacted clay best
Low yield areas with plants, such as grass or
groundcover
Conveyance Systems Direct water from catchments to storage containers
Roof conveyance systems use canals or gutters and
downspouts to direct water into storage containers
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Complex Rainwater
Harvesting SystemsStorage
Storage makes rainwater available when needed.
Filtration water should be filtered before storage.
Filtration considerations include:
Degree of filtration depends on size of distributiontubing and emission devices used; water should be
filtered enough so that particles do not clog distributionsystem
Type of filter inline, leaf screens, diversion byroofwashing to a PVC standpipe
Containers may be made of polyethylene, fiberglass, wood,concrete, or metal; underground or above-ground
Distribution System Network of pipe
Use valves for a gravitational system and a pump for an electricsystem to control flow.
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Did you know that?
A well is not a storage tank to holdwater. It helps to collect the rain
water and charge it underground andlater bring it out.Roof water and run off water can be
diverted into dried up bore wells after fillingof the wells with pebbles and river sand.There should be an effective arrangement
for desilting before diverting the water
into these wells.
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Designing and Building a Complex
Rainwater Harvesting System
Step 1: Site Analysis
Draw the site to scale, using arrows to plot existingdrainage patterns, and showing high and low areas.
Identify possible catchments, such as pavements, roof
surfaces, and bare earth. Identify areas requiring irrigation and sites near them
where storage could be located (above ground orunderground).
Plan ways to move water from catchments to storage
containers or holding areas, using gravity when possible.
Plan ways to move water between landscaped areas.
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Designing and Building a Complex
Rainwater Harvesting System
Step 2: Calculations
Calculate SupplySUPPLY (gal) = Rainfall (in) x 0.623 x Catchment Area (sq ft) x Runoff Coefficient
Multiply rainfall in inches by 0.623 to convert inches to
gallons per square foot. Multiply the result by the area of the catchment in square
feet.
Multiply this result by the runoff coefficient to obtain the
available supply. The runoff coefficient is the percentage of total rainfall that can
be harvested from a particular source.
Runoff coefficients can be found in hydrology textbooks.
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E X A M P L EA = 45 x 25
B = 20 x 25Catchment Area = 1625 sq. ft.
No. of Family Members = 5
Run off Coefficients :-
Character of Surface High Low
Roof
Metal, Gravel, Ashfalt 0.95 0.75
Paving
Concrete, Ashfalt 0.95 0.70
Brick 0.85 0.70
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Example 1: Calculating Supply
32.921.962.583.863.002.572.034.304.722.601.891.751.66
47.843.694.194.504.333.833.185.355.153.603.362.983.68
9.430.770.420.811.611.751.490.870.380.230.260.390.45
34.732.572.574.112.422.032.123.235.153.203.062.371.90
34.722.533.023.992.882.512.033.425.122.632.362.022.21
AnnualDecNovOctSepAugJulJunMayAprMarFebJanCitiesP
Q
R
S
T
Average Monthly Rainfall (inches)
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Example 1: Calculating Supply
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Water requirements and Usage by a family. (in India)
(According to I.S. - 1172)
Litres per day per personBathing 20Flushing 40
Washing clothes 25
Washing utensils 20Gardening 23Total 128
Total Water required by complete family
Per Day = 5 x 128 = 640 LtrsPer Month = 30 x 640 = 1920 Ltrs
= 507.2 Gallon
Example 1: Calculating Demand
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Designing and Building a Complex
Rainwater Harvesting System
Calculations Calculate Maximum Storage/Supplemental Water
Requirements Use checkbook method to balance harvested supply
and demand per month. Determine cumulative storage by adding the previous
months cumulative storage to the current monthsbalance.
Determine storage container requirements by notingthe highest cumulative storage value.
When the cumulative storage goes to zero,supplemental water will be needed.
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LEGISTATION
IN CHENNAI , RWH MADE COMPULSORY.
IN DELHI BLDG. BYE LAWS MODIFIED MAKING RWH
MANDATORY FOR NEW BLDGS. ON PLOTS > 100 Sqm.
DELHI GOVT. HAS COME WITH AN INCENTIVE TO
REIMBORSE 50% COST OF RWH STRUCT. (MAX 50000)
FOR CERTAIN COLONIES
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CONCLUSIONOUR MISSION SHOULD BE :
CONSERVATION OF WATER
SINCE WE CANNOT PRODUCE ENERGY
BUT WE CAN SAVE IT BY PREVENTING
WASTAGE.
IN THE SAME WAY WE CANNOT
PRODUCE WATER BUT WE CAN PREVENT
IT FROM WASTAGE AND PROTECT OURFUTURE.
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NOW BE READY FOR
A GAME
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