water supply systems lecture 1
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dr Patryk Wjtowicz
Water Supply Systems
Lecture notes 1
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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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History of water distribution systems
Early pipelines were made by drilling stones,wood, clay and lead 1455- first cast iron pipe
ceramic pipelines
wooden pipes
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History of water distribution systems
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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History of water distribution systems
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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History of water distribution systems
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