Advance Water Distribution Modeling and Management: Shuming Liu, THU

Advance water distribution modeling and
management
Shuming Liu, THU
Aim of course
• To understand the modeling and optimization techniques
used in water distribution system management
• To understand the problems existing in water distribution
system (WDS)
• To gain the capability of solving water distribution system
management problem using modelling and optimization
techniques
Pre-requirement
• Preliminary knowledge of water distribution system
• Preliminary knowledge of modelling
• Preliminary knowledge of optimization
• Preliminary knowledge of MATLAB
Course content
Part one: to learn how to simulate pipe hydraulic and water
quality (week 1-6)
Part two: to understand the challenges faced in water
distribution system (week 7-9)
Part three: to learn how to tackle leakage problem using
optimization and modelling techniques (week 10-14 )
Course assignment (week15-16)
Course evaluation
• 5% attendance +25% lab + 70%

course assignment
• Total credits: 3
Lecture 1: Introduction of
WDS modelling fundamental
Shuming Liu
SOE, Tsinghua University
Aim of lecture
• To introduce what water distribution modeling is
– by giving an overview of the basic distribution system
components,
– defining the nature and purpose of distribution system
simulation
– and outlining the basic steps in the modeling process
• To review the principle of hydraulics and water
quality analysis that are frequently employed in
WDS modeling software
Anatomy of a water distribution system (WDS)
What is a water distribution
network?
• A water distribution network (WDN) is used to transfer
water from water plant to end users. Within this process,
both water quality and quantity are concerned.
• A WDN normally includes pipe, valves, pump, water tank
etc.
• Within a WDN, not only water pressure, but also water
quality varies temporally and spatially.
Features of WDN management
• Data scarcity: millions of nodes and links, data

availability is always a problem
• Uncertainty: for example, water demand
• Less accessibility: underground
Anatomy of a water distribution system (WDS)
• Transmission/trunk mains:
– Consist of components that are designed to covey large
amounts of water over great distance
• Distribution mains:
– An intermediate step toward delivering water to the end
customers, which are smaller in diameter than trunk mains.
System configurations
• Looped and branched systems
– Branched system: low cost, water have only one possible path
from the source to a customer, low reliability
– Looped system: high cost, more than one possible path from
the source to a customer, higher reliability
Looped and branched networks
Looped and branched networks after network failure
What is a WDS simulation?
• Simulation: refers to the process of imitating the behavior of one
system through the functions of another or using a mathematical
representation of the real system
• With simulation, it is possible to understand the hydraulics and
water quality features of a WDS without sampling throughout.
• Simulation can be used to predict system responses to events
under a wide range of conditions without disrupting the actual
system.
Scenario 1 Scenario 2
Scenario 3 Scenario 4
Type of WDS modeling
• Steady-state simulations (SSS):
– Represent a snapshot in time and are used to
determine the operating behavior of a system
under static conditions.
• Extended-period simulations (EPS):
– Represent the system behavior over time with
pre-defined nodal demand
• Real time simulations (RTS):
– Represent the system behavior the real time
nodal demand
Applications of water distribution models
(WDMs)
• Steady-state simulations :
– Long-range master planning: new development and rehabilitation
– Fire protection studies
• Extended-period simulations
– Water quality investigations
– Energy management
– Daily operations
• Real time simulations
– Emergency response
– System troubleshooting
– ……
Modeling process
What is known and what is unknown?

A brief history of water distribution technologies
• 1500 BC. –first water distribution pipes used in Crete;
• 1455- first cast iron pipe
• 1906- Hazen-Williams equation developed
• 1960s and 1970s-earliest pipe network digital models created;
• 1970s- early attempts to optimize water distribution design
• 1980s- water quality modeling first developed
• 1993- introduction of water quality modeling tool
• 2001- security awareness
• 2002- integration with GIS
• 2009- real time modelling
Fluid dynamics
• The flow of water through municipal water systems is almost always
turbulent, except in the periphery where water demand is low and
intermittent, and may result in laminar and stagnant flow conditions.
• In laminar flow, the fluid particles travel in parallel layers, producing strong shear stress between layers.
The head loss is primarily a function of the fluid viscosity, not the internal pipe roughness.
• Turbulent flow is characterized by eddies that produce random variations in the velocity profiles. The
mean velocity profile exhibits less variation across the pipe than the one for laminar flow.
Energy concepts
• Fluids possess energy in three forms:
– fluid’s movement (kinetic energy): velocity head
– elevation( potential energy): elevation head
– pressure (pressure energy): pressure head
Energy concepts
Energy and hydraulic grade lines
hL
V
2 • Energy grade line (EGL):a line
2g
plotted of total head versus
distance through a system
• Hydraulic grade line (HGL): the
sum of the elevation head and
P pressure head

Friction losses
• When a liquid flows through a pipeline, shear stresses
develop between the liquid and the pipe wall. This shear
stress is a result of friction.
• Its magnitude is dependent on
– the properties of the fluid,
– the flow speed,
– the internal roughness,
– and the length and diameter of the pipe.
Friction losses
Free body diagram of water flowing in an inclined pipe
2
V1 / 2 g
2
V2 / 2 g
P1 /  P2 / 
P 2 A2
 0 NL 
P1 A1
Z2
Z1 A L
Hazen-Williams equation
Cf L
h L  1.852 4.87 Q
1.852
C D
where hL=head loss due to friction(ft, m)

L=distance between sections 1 and 2(ft, m)
C=Hazen-Williams C-factor
D=diameter(ft, m)
Q=pipeline flow rate(cfs, m3/s)
Cf=unit conversion factor(4.73 EnglishUnit, 10.7 System International Unit)
Minor losses
Valve coefficient /equivalent pipe length
• Valve manufactures can provide a chart of percent
opening versus valve coefficient , which can be related to
the minor losses.
• The minor losses can be accounted for by adding an

equivalent length of pipe.
Energy gains--pump
• Pumps are used in a WDS to overcome elevation
differences, friction losses, and minor losses.
• Mechanical energy  total head
• Pump head is a function of the flow rate through the
pump.
• Centrifugal pumps are the most frequently used pumps in
WDSs.
Head-Discharge relationship
• Head-discharge relationship (head characteristic curve) defines the relationship
between the head that the pump adds and the amount of flow that the pump passes.
Variable-speed pumps
• A centrifugal pump’s characteristic curve is fixed for a
given motor and impeller diameter.
• For variable-speed pumps, the following affinity laws is
applicable.
QP1 / QP 2  n1 / n2
hP1 / hP 2  (n1 / n2 ) 2
Where QP1=pump flow at speed 1 (L3/T)
n1=pump speed 1 (1/T)
hP1=pump head at speed 1 (L)

Relative speed factors for variable-speed pumps
Pump discharge rate is directly

proportional to pump speed, and
pump discharge head is
proportional to the square of the
speed. Using this relationship,
once the pump curve at any one
speed is known, then the curve at
another speed can be predicted.
speed
n
fullspeed
System head curves
• The amount of head the pump must add to overcome elevation
differences is dependent on system characteristics and topology.
This is referred to as static head or static lift.
• Static head is independent of the pump discharge rate.
• Friction and minor losses, however, are highly dependent on the
rate of discharge through the pump.
• A system head curve = friction and minor losses + static head for
a series of discharge rates
System head curves
A family of system head curves
Pump characteristic curve VS System head
curve
• The PCC is a function of the pump and independent of
the system.
• The SHC is dependent on the system and independent of
the pump.
• The PCC is fixed for a given pump at a given speed, it is
a unique one.
• The SHC is continually sliding up and down as tank water
levels and demand change.
Reference books
• Water distribution systems, Savic and Banyard, ICE
publishing.
• Advanced Water Distribution Modeling and Management,
Colleen Totz and Kristen Dietrich, Bentley.
Homework
1. Compute the pipe resistance coefficient, KP , for the
following pipelines using Hazen-Williams equation.
2. What type of flow do you think normally exists in water

distribution systems: laminar, turbulent, or transitional?
Justify your selection with sound reasoning.

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Advance water distribution modeling and

• 5% attendance +25% lab + 70%

• Data scarcity: millions of nodes and links, data

What is known and what is unknown?

where hL=head loss due to friction(ft, m)

• The minor losses can be accounted for by adding an

Where QP1=pump flow at speed 1 (L3/T)

n1=pump speed 1 (1/T)

hP1=pump head at speed 1 (L)

Pump discharge rate is directly

2. What type of flow do you think normally exists in water

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