Water Supply Systems Lecture 1

8/10/2019 Water Supply Systems Lecture 1

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dr Patryk Wjtowicz

Water Supply Systems

Lecture notes 1

Monday 1 December 14


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Contents

Introduction to water distribution systems History and evolution of water supply systems

Primary function and design criteria of WDS

Anatomy of water supply systems Layouts of water distribution system

Criteria and classification of water systems



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Water distribution system*

Water distribution system (WDS) is a network ofpipelines and structures that distribute water tothe consumers

WDS is designed to adequately satisfy the waterrequirement for a combination of purposes: Domestic

Commercial Industrial

Firefighting purposes

(*also: Water Supply System - WSS)



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History of water distribution systems

The oldest water distribution systems discovered on the island ofCrete are 3500 years old (first usage of pipes). The City of Knossosdevelops an aqueduct system that uses tubular conduits to conveywater. Other ancient civilizations have had surface water canals,but these are probably the first pipes

250 B.C.- Archimedes principle developed 100 A.D.- Roman aqueducts

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Figure 1.Minoan water transfer projects: The proposed course (A- B) of the aqueduct at Knossoswith

higher spring elevation (Angelakis et al.,2007) (left) and water supply pipes (terracotta pipe sections):cross section and dimensions (upper) and today view (down) (Koutsoyiannis et al., 2008) (right).



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Early pipelines were made by drilling stones,wood, clay and lead 1455- first cast iron pipe

ceramic pipelines

wooden pipes



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1664- Palace of Versailles: 35 km long cast ironwater main (flanged joints) from Marly-on-Seineto the Palace of Versailles (still in operation).Used for 1400 fountains of Sun King Louis XIV

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1738 Bernoulli publishes Hydrodynamica. 1770 Chezy develops head loss relationship

1845 Darcy-Weisbach head loss equationdeveloped

1920s Cement-mortar lining of water mains 1936 Hardy Cross method developed

1938 Colebrook-White equation developed



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1960s and 70s Earliest pipe network digitalmodels created 1980 Personal computers introduced

2001 Automated calibration 2002 Integration with GIS

A computer punch card



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Primary function of WDS

The purpose of the water distribution system is todeliver water to consumer with appropriate quality,quantity and pressure

Distribution systems typically also provide storage,as well as provide flow and pressure adequate forfire protection.

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System design criteria

Water qualityshould not get deteriorated in the mainand distribution pipelines on the way from the treatmentfacility to the customer

System should be capable of supplying water to allintended (and planned) places with sufficient pressurehead

System should be also capable of supplying the requiredamount of water during fire fighting



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System design criteria contd.

The layout of the system should be such that noconsumer would be without water supply, during therepair or maintenance of any section of the waternetwork

All the distribution pipelines should be preferably laidabove the sewer lines Pipes should be water-tight to keep water losses due

to leakage to the minimum



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System configuration - anatomy of WDS

Water distribution system

water sources and intakeworks

treatment works andstorage

transmission mains

distribution network

!raw water is transported to treatment plant forprocessing

!water after treatment is stored in clear water

reservoirs

!water reservoirs provides a bu!

er for water demandvariation (treatment plant is designed for average dailydemand)

!rivers, lakes, springs

!man-made reservoirs

!groundwater sources (bores and wells)

!intake structures and pumping stations

to extract water from source

!water is carried over long distances throughtransmission mains

!pumping main if pressure head is created by

pumping!gravity main if flow maintained by gravitational

potential (on account of elevation di!erence)

!There are no intermediate withdrawals

!distribution network delivers water toconsumers through service connections

!water distribution network may have

di!erent layout (branched or looped)



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SYSTEM

COMPONENTS

SUBCOMPONENTS

DISTRIBUTION

PIPING

VALVES

IPESALVE

IPE

ANKS

DISTRIBUTION

STORAGE

WATER DISTRIBUTION

SYSTEM

CONTROLS

PIPING

UMPING

POWER

TRANSMISSION

RIVER

PUMPING STATION

ELECTRICAL

PUMP

STRUCTURAL

SUB SUB OMPONENTS

FIGURE 1 15

Hierarchical relationship of components, subcomponents, and sub-subcomponents for a water distribution system

Cullinane,1989 .



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Distribution System Layout

!Grid or loop systems provide greaterflow for fire protection and reduce thenumber of dead-end lines

Water distribution mains may be laid out in grids, loops, or branches (muchlike a tree). Two basic types can be distinguished:

!Branched layouts result in a number ofdead-end lines that can lead tobacteriological, taste, and odor problems

!In addition, they require more frequent

flushing

Usually we have a mix of

branched and loopedlayouts - depends heavily onthe history and general layoutplan of the city roads andstreets

Branched (dead-end) network

layout

Looped network

layout



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Layout of network

Urban water networks have mostly loopedconfigurations Rural water networks have branched (dead-end)

configurations

The cost of a WDS depends upon properselection of the geometry of the network. The

selection of street layout adopted in the cityplanning is important to provide a minimum-costwater supply system



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Advantages of the branched pattern

The design calculation is simple and easy A smaller number of cut-off valves are required

and the operation and maintenance cost is low

Pipe-laying is simple



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Disadvantages of the branched pattern

The system is less successful in maintaining satisfactory pressure in theremote areasand is therefore not favoured in modern waterworks practice

One main pipeline provides the entire city, which is quite risky. Any defect,damageor breakage at one point of this line will disrupt the supply of water beyond

that point, cutting off service to the whole area. This could be dangerous,especially if there is a fire

The head loss is relatively high, requiring larger pipe diameter, and/or largercapacities for pumping units. Water hammer could also cause burst of lines

Dead ends at line terminals might affect the quality of water by allowingsedimentation and encouraging bacterial growth due to stagnation A large number of scour valves are required at the dead ends, which need

to be opened periodically for the removal of stale water and sediment

The discharge available for fire fighting in the streets will be limited due tohigh head loss in areas with weak pressure



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Looped network configurations patterns

The most common water supply configurationsof looped water supply systems are: gridiron pattern

circular or ring pattern radial pattern



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Gridiron pattern

In the gridiron systemthe main supply line runs through the

center of the area and sub- mains takeoff from this in perpendiculardirections

The branch lines interconnect the sub-mains This system is ideal for cities laid out in a rectangular plan (e.g.

New York, most city centres)

All of the pipelines are interconnected and there are no dead ends Water can reach a given point of withdrawal from several directions



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Advantages of gridiron pattern

The free circulation of water, without any stagnationor sediment deposit, minimizes the the chances ofpollution due to stagnation

Water is available at every point, with minimum lossof head, because of the pipeline interconnections

Enough water is available at streets fire hydrants,as the hydrant will draw water from the various

branches of water lines

During repairs, only a small area of distribution isaffected



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Disadvantages of gridiron pattern

A large number of cut-off valves are required The system requires longer pipe lengths with

larger diameters

The hydraulic calculations of discharge,pressure and velocities in the pipes is difficultand inconvenient

The cost of pipe-laying is higher



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Circular (ring) pattern

In circular (also ring) pattern the supply main forms a ringaround the distribution area

The branches are connected cross-wise to the mains and alsoto each other

Circular pattern is most reliable for a town with well plannedstreets and roads



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Advantages and disadvantages of circular pattern

The advantages and disadvantages of circularsystem are the same as those of the gridironsystem

Only in case of fire, a larger quantity of water isavailable, because the available length of thedistribution main is much larger



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Radial pattern

In a radial system, the whole area is divided into a number ofdistribution districts Each district has a centrally located distribution reservoir (elevated)

from where distribution pipes run radially towards the periphery of the

distribution district

This system provides swift service, without much loss of head The design calculations are much simpler



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Water systems classifications - water pressurecriterion

There are two basic types of water supply systems tocreate water pressure within the distribution system: Gravity feedsystems

Pumping pressuresystems

primary pumpingstation

secondary pumping station

tertiary pumping station (orbooster station)



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Gravity water distribution

Gravity distributionis possible when the treated watersource is located at some needed elevation above thesupplied community

In this type of system, sufficient pressure is available due togravity to maintain water pressure in the mains for domesticconsumption and fire service demand.

This is the most reliable and economicalmethod ofdistribution

Higher pressures for firefighting, however, requires the useof mobile fire department pumpers and, in some cases,

stationary booster pumps on the water system to provide

needed fire flows at representative fire hydrants with a

required residual pressureMonday 1 December 14


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Pumps and elevated storage

Through the use of pumps and elevated storage,the excess water pumped during periods of lowconsumption is stored in elevated tanks orreservoirs

During periods of high consumption, the storedwater supplements the water that is being pumped

This method allows fairly uniform flow rates andpressures throughout the water system

Since the stored water supplements the supplyused for fires and system breakdowns, this method

of operation is fairly reliableMonday 1 December 14


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Pumps without storage

When stationary pumps are used to distribute water, and nostorage is provided on the distribution system, the pumps forcewater at the required volume and pressure directly into the mains

This is the least desirable type of distribution system because apower failure could interrupt the water supply

As water consumption varies, the pressure in the water mains ismost likely to fluctuate

To conform to varying rates, several pumps are made available toadd water output when needed, a procedure requiring reliable

and tested automated control at the water plant

Another disadvantage is the fact that the peak power demand ofthe water plant is likely to occur during periods of high electricpower consumption, thus increasing power costs to operate the

water systemMonday 1 December 14


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Classification of water distribution systems - watersource criterion

Community water systems can be divided into four basic

classifications according to the water source:

High or low reservoirsthat hold water for gravity feed Pumping station systemswhere the raw water is pumped from

the source point to the treatment plant and then either pumped

directly into the distribution system or into storage to be used ondemand by the community

Pumps at well sitesthat pump water to the treatment facility.Based on the difference in elevation between the treatment facility

and the community to be served, the water may flow by gravity

through the distribution systems, or there may be the need for

another pumping station

A combination of gravity flow and one or more pumpingstationsto transport the water from the source point to all of the

water demand points on the distribution systemMonday 1 December 14


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High-level reservoir system

In a high-level reservoir systema water source must be at proper elevation above thetreatment facility in order to provide sufficient head pressure so that no pumping station isrequired (usually at least 30 meters)

If there is sufficient elevation difference between the treatment facility and the distribution pipingin the community, it is possible to design a water system that does not require pumping stations

The head pressure for supplying water to the distribution system must be sufficient to meet bothconsumer demand and needed fire flows at any conditions

Gravity feed systems are highly reliable under all weather conditions that may cause disruption tothe pumped systems. There is no mechanical component to break down or fail when the powersource goes down.

This is a very economical system since there is no substantial power requirement to run thewater system

I I I I



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Low level reservoir systems

A low level reservoir systemstypically require a pumping station totransport water to the treatment plant If the land area is relatively flat, a second pumping stationto pump

treated water directly to the distribution system or to elevated storage

to provide the required pressure and volume to meet instantaneous

flow demand

The elevated storage can be designed to minimize the direct pumpingrequirements



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Direct pumping systems

Direct pumping systemsfeeds water to thetreatment plant and then a second pumping systemtransports water to a storage holding area (clear well,standpipe storage tank)

This combination of pipe and tank minimizes the timethe pump or pumps actually have to run

PUMP STATION PUMP STATION

FILTRATION

PLANT

WELL

CASING

DISTRIBUTION

SYSTEM



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Pumping station at well sites + gravity storage

In pumping station from well sites to a gravity storage,one ora field of drilled well, feed water to a ground-level pumping station The treated water either flows by gravity to the distribution system

or is pumped to one or more elevated storage tanks

Elevated tanks may be located at the beginning, centre or end ofwater network



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Composite water supply systems

In some specific conditions of areas served by the water system, especially

topography may require using a composite system(mixed type) that usescomponents from more than one of the typical water systems

Examples of mixed water supply systems: Adding pumping stations to a gravity reservoir system to increase

pressure and volume during peak demand periods (esp. for a fire flowrequirement)

Booster pumping stations may be installed where there is a need formore than one service level based on pressure demand

Direct pumping into the distribution system may be supplemented bygravity tanks that "float" on the system to maintain pressure and flowcharacteristics during different demand periods through the day andnight

Gravity tanks are especially useful for improving the reliability of anywater system, care must be taken to allow for proper mixing of water

stored



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Supplementary reading

Larry Mays (2000) Water Distribution SystemHandbook, Chapter 1, McGraw-Hill, New York.

Assignment:Prepare short paper (4 A4 pages) summarizingall important information from supplementaryreading.Paper should include introduction and severalsubchapters.



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Literature

Mays et al. (2000) Water distribution systems handbook,

McGraw-Hill, New York.

Savic et al. (2011) Water distribution systems, ICEPublishing, Thomas Telford Ltd, London.

Swamee and Sharma (2008) Design of water supply pipenetworks, Wiley. Computer Modeling of Water Distribution Systems - Manual

of Water Supply Practices, M32 (3rd Edition). American

Water Works Association (AWWA).

Online version available at: http://app.knovel.com/hotlink/

toc/id:kpCMWDSM0G/computer-modeling-water/computer-

modeling-water
http://app.knovel.com/hotlink/toc/id:kpCMWDSM0G/computer-modeling-water/computer-modeling-waterhttp://app.knovel.com/hotlink/toc/id:kpCMWDSM0G/computer-modeling-water/computer-modeling-waterhttp://app.knovel.com/hotlink/toc/id:kpCMWDSM0G/computer-modeling-water/computer-modeling-waterhttp://app.knovel.com/hotlink/toc/id:kpCMWDSM0G/computer-modeling-water/computer-modeling-waterhttp://app.knovel.com/hotlink/toc/id:kpCMWDSM0G/computer-modeling-water/computer-modeling-waterhttp://app.knovel.com/hotlink/toc/id:kpCMWDSM0G/computer-modeling-water/computer-modeling-waterhttp://app.knovel.com/hotlink/toc/id:kpCMWDSM0G/computer-modeling-water/computer-modeling-waterhttp://app.knovel.com/hotlink/toc/id:kpCMWDSM0G/computer-modeling-water/computer-modeling-water

Water Supply Systems Lecture 1

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