Microsoft Power Point - Rain Water Harvesting [16 Nov 2008]

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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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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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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Documents

Microsoft Power Point - Rain Water Harvesting [16 Nov 2008]