Project and Report

Hamza Khalil

2011-Ag-2902

Objectives

History

RWH Definition

Importance of RWH in Punjab

RWH techniques

Factors affecting RWH

RWH components

Storage capacity calculation by Mass curve

RainXchange system

History

Around the third century BC, the farming

communities in Baluchistan (in present

day Pakistan, Afghanistan and Iran), and Kutch

(in present-day India) used rainwater harvesting

for irrigation.

Karez in Baluchistan

Rainwater Harvesting - Definition

Accumulating and storing of rainwater for reuse

before it reaches the aquifer.

Used to provide drinking water, water for

livestock, water for irrigation, as well as other

typical uses.

Rainwater collected from the roofs of houses

and local institutions can make an important

contribution to the availability of drinking water.

The climate in Pakistan

Pakistan is a predominantly dry country. The flat

areas in the south and centre have a desert-like

climate. May and June are the hottest months, when

it is 40 to 45 °C. The best travel period is from

December to March, when it is relatively cool. The

north of the country is visited by the monsoon in

July and August. In a short space of time a lot of

rain can fall and there can be heavy storms.

Importance of RWH in Punjab

The north Punjab areas Rawalpindi, Attock,

Jhelum and Chakwal natives rely on water

sources from rainfall and ground water. Pakistan

is known as an arid country having subtropical

climate and it may be divided into two regions.

1. Indus plain

2. Highlands

Dry climate is dominant in most of the country

parts except northern highlands. On an average

about 750mm of rain fall occurs annually in

northern areas. Baluchistan receives about

250mm of rainfall annually.

There is dire need to address the water shortage

issues across the country.

Need For Rainfall Harvesting in Urban

Areas of Punjab

Groundwater reservoirs have been declining in

urban areas due to rapid urbanization.

Excessive use of groundwater is causing

deterioration of water quality and drying up of

water wells.

The sweet water becoming scarce in urban

areas of Punjab Province.

Up-coning of deep saline water has started in

some parts of Punjab.

Name of city Faisalabad

Population( million) 2.83

There is a need to realistically estimate and

manage water resources for sustainable

development.

Storage of rain water on surface for future

use.

Recharge to ground water for sustainable

water supply in urban areas.

Rainwater harvesting techniques

There may be two rainwater harvesting

techniques for the accumulation of rainwater

that may be used for different purposes.

1. Land-based.

2. Roof-based.

Land-based

When the infiltration requirements of the soil have

been fulfilled and excess amount of rainwater flow

as overland flow and then become the runoff and this

runoff accumulated in reservoirs for agriculture

growth purposes, in ponds for recharging purposes

and in tanks for household, this type of rainwater

harvesting technique is called land-base.

Roof-based

The rainwater that falls on the top of the roof is

harvested for a domestic purpose, small scale

agriculture purposes and is also sometimes used

for drinking water because this water is usually

collected from clean surfaces. This type of water

harvesting is called roof-based water harvesting.

Roof catchment systems

Domestic consumption

Rock catchment systems

Ground catchment systems

Small scale irrigation, nurseries, livestock consumption

Check and sand dams,

hafirs

Factors affecting RWH system design

Rainfall quantity (mm/year)

Rainfall pattern

Collection surface area (m2)

Runoff coefficient of collection (-)

Storage capacity (m3)

Daily consumption rate (liters/capita /day)

Number of users

Cost

Alternative water sources

RWH System Components

Catchment Area/Roof

- the surface upon which the rain falls

Gutters and Downpipes

- the transport channels from catchment

surface to storage

Leaf Screens and Roof washers

- the systems that remove contaminants and

debris

Cisterns or Storage Tanks

- where collected rainwater is stored

Conveying

- the delivery system for the treated rainwater,

either by gravity or pump

Water Treatment

- filters and equipment, and additives to

settle, filter, and disinfect

Design considerations for rooftop

catchment systems

The material of the catchment surfaces must benon-toxic and not contain substances which impairwater quality.

Roof surfaces should be smooth, hard and densesince they are easy to clean and are less likely tobe damaged and shed materials into water.

Precautions are required to prevent the entry ofcontaminants into the storage tanks.

No overhanging tree should be left near theroof.

All gutter ends should be fitted with a wiremesh screen to keep out leaves.

The storage tank should have a tight-fitting roofthat excludes light, a manhole cover and aflushing pipe at the base of the tank.

The nesting of the birds on the roof should beprevented.

A sloped bottom and a provision of a sump

and a drain are useful for collection and

discharge of settled grit and sediment.

Taps/faucets should be installed at 10 cm

above the base of the tank as this allows any

debris entering the tank to settle on the bottom

where it remains undisturbed, will not affect

the quality of water.

Design Consideration

An estimate of mean annual runoff from a givencatchment can be obtained using the equation.

S = R * A * C

Where

S = Rainwater supply per annum

R = mean annual rainfall

A = Area of the catchment

C = Runoff coefficient

Mean annual runoff

Catchment Area Size

Runoff depends upon the area and type of the

catchment over which it falls as well as surface

features.

Runoff coefficient for any catchment is the ratio of

the volume of water that runs off a surface to the

volume of rainfall that falls on the surface.

(C = V1/V2)

Type of Catchment Coefficients

Tiles 0.8 – 0.9

Corrugated metal sheets 0.7 – 0.9

Storage System

There are several options available for the storage

of rainwater. A variety of materials and different

shapes of the vessels have been used. In general,

there can be two basic types of storage system.

Underground tank or storage vessel

Ground tank or storage vessel

The choice of the system will depend on several

technical and economic considerations like, space

availability, materials and skill available, costs of

buying a new tank or construction on site, ground

conditions, local traditions for water storage etc.

Selection of System

Storage capacity

Knowledge of the rainfall quantity and

seasonality, the area of the catchment surface

and volume of the storage tank, and quantity

and period of use required for water supply

purposes is critical.

A better estimate of storage requirement can be

made using the mass curve technique based on

rainfall and water demand pattern.

Cumulative rainfall runoff and cumulative water

demand in year is calculated and plotted on the

same curve.

The sum of the maximum differences, on the

either side, between the rainfall curve and water

demand curve gives the size of the storage required.

Storage capacity calculations

Faisalabad

Rain fall harvest =

Area*Amount of Rain*Efficiency

Calculations

Area of catchment = 100*100 = 10,000m2

= 1ha

Runoff coefficient = .6

ET0 For Faisalabad = 6.5 mm/day

Kc for wheat = 1.2

CWR = 7.8 mm/day

Cropping area = 400 m2

Average daily demand = 3.12 m3

Yearly demand = 3.12*365 = 1138.8 m3

Average monthly demand = 94.9 m3

Approximately = 95 m3

Calculation of Required storage Capacity

Required storage capacity = (1734+16)= 1750 m3

Mass curve for the calculation of required

storage capacity

Faisalabad(1951-2004)

Required storage capacity = 1226 m3

The RainXchangeTM allows you to collect

thousands of gallons of water anywhere, even in

the Desert.

THE RAINXCHANGE™ SYSTEM

RainXchange system

THE RAINXCHANGE™ SYSTEM

The Aquascape RainXchange™ Harvesting

Systems are a revolutionary design that combines a

recirculating decorative water feature with a sub-

surface rainwater harvesting collection system.

Clean, Filtered Water Collection & Storage

While you enjoy the benefits of a decorative water

feature, the RainXchange™ Rainwater Harvesting

System filters the stored water to prevent

stagnation and growth of unhealthy bacteria.

The RainXchange™ Rainwater Harvesting

System reveals only a beautiful water

feature that integrates easily into existing

landscape.

Collecting and storing the water

underground maintains the integrity and beauty

of your home and landscape.