Water distribution system handbook (part 1)

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DISTRIBUTION

SYSTEMS

HANDBOOK

Larry W Mays, Editor in Chief

Department of Civil and Environmental Engineering

Arizona State University Tempe, Arizona

McGraw-Hill

New York • San Francisco • Washington, D.C • Auckland • Bogota • Caracas • Lisbon

• London • Madrid • Mexico City • Milan • Montreal • New Delhi • San Juan

• Singapore • Sydney • Tokyo • Toronto

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Library of Congress Cataloging-in-Publication Data

Water distribution systems handbook/Larry W Mays, ed.

p cm.

Includes bibliographical references.

ISBN 0-07-134213-3

1 Water—Distributions Hanbooks, manuals, etc.

2 Water—supply engineering Handbooks, manuals, etc I Mays, Larry W.

A Division of The McGraw-Hill Companies

in the United States of America Except as permitted under the United States

Copyright Act of 1976, no part of this publication may be reproduced or distributed in

any form or by any means, or stored in a data base or retrieval system, without the

prior written permission of the publisher.

5 6 7 8 9 0 DOC/DOC 0 4 3 2 1 0

ISBN 0-07-134213-3

The sponsoring editor for this book was Larry Hager and the production supervisor

was Sherri Souffrance It was set in Times Roman by Compuvision.

Printed and bound by R R Donnelley & Sons Company.

This book was printed on acid-free paper.

McGraw-Hill books are available at special quantity discounts to use as premiums and

sales promotions, or for use in corporate training programs For more information,

please write to the Director of Special Sales, McGraw-Hill, Inc., Two Penn Plaza,

New York, NY, 10121-2298 Or contact your local bookstore.

Information contained in this work has been obtained by The

McGraw-Hill Companies, Inc ("McGraw-Hill") from sources

believed to be reliable However, neither McGraw-Hill nor its

authors guarantee the accuracy or completeness of any information

published herein, and neither McGraw-Hill nor its authors shall be

responsible for any errors, omissions, or damages arising out of

use of this information This work is published with the

under-standing that McGraw-Hill and its authors are supplying

informa-tion but are not attempting to render engineering or other

profes-sions) services If such services are required, the assistance of an

appropriate professional should be sought.

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Bayard Bosserman II Boyle Engineering Corporation (CHAPTER 5)

Francious Bouchart Heriot-Watt University (CHAPTER 18)

Donald V Chase University of Dayton (CHAPTER 15)

Robert Clark U S Environmental Protection Agency (CHAPTER 13)

Edwin E Geldreich Consulting Microbiologist (CHAPTER 9)

Fred E Goldman Goldman, Toy, and Associates (CHAPTER 16)

Ian Goulter Swinburne University of Technology (CHAPTER 18)

Walter M Grayman Consulting Engineer (CHAPTER 9, 11)

Bryan W Karney University of Toronto (CHAPTER 2)

Gregory J Kirmeyer Economic and Engineering Services, Inc (CHAPTER 11) Kevin Lansey University of Arizona (CHAPTER 4, 7)

Srinivasa Lingireddy University of Kentucky (CHAPTER 14)

James W Male University of Portland (CHAPTER 17)

C Samuel Martin Georgia Institute of Technology (CHAPTER 6)

Larry W Mays Arizona State University (CHAPTER 1,4, 16, 18)

Lindell E Ormsbee University of Kentucky (CHAPTER 14, 16)

Lewis A Rossman U S Environmental Protection Agency (CHAPTER 9, 12)

A Burcu Altan Sakarya Middle East Technical University (CHAPTER 16, 18)

Yeou-Koung Tung Hong Kong University of Science and Technology (CHAPTER 18) Jim Uber University of Cincinnati (CHAPTER 16)

Thomas M Walski Pennsylvania American Water Co (CHAPTER 8, 10, 17, 18) Mark Ysusi Montgomery Watson (CHAPTER 3)

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At the beginning of year 2000 this is an exciting time to be involved in writing about thedelivery of safe drinking water Today's increased awareness and concern for safe drink-ing water on a national and international basis, coupled with limited budgets of not onlydeveloping countries but also of developed countries, has generated an exponentialincrease in interest in the future of water distribution

In the U S and in other developed countries the populations take the ability to havesafe drinking water at any time and place for granted According to the World HealthOrganization and the United Nations, however, the needs for urban water and rural watersupply are tremendous The urban population in developing countries in 1990 withoutaccess to safe drinking water was approximately 243 million people, and in rural areas indeveloping countries was approximately 989 million people, for a total of 1,232 millionpeople without access to safe drinking water The expected population increase in urbanareas in developing countries from year 1990 to 2000 is expected to be 570 million peo-ple, making the total in urban areas requiring the service of safe drinking water to be 813million people The expected population increase in rural areas in developing countriesfrom 1990 to 2000 is expected to be 312 million people, making the total in rural areasrequiring the service of safe drinking water to be 1,301 million people The total popula-tion needs in developing countries requiring safe drinking water by year 2000 is 2,114million people

The Water Distribution Systems Handbook, referred to herein as the Handbook, has

been an extensive effort to develop a comprehensive reference book on water distributionsystems A substantial amount of new knowledge concerning the design, operation, andanalysis of water distribution systems has accumulated over the past decade In particular,many new developments have taken place on the subjects of water quality of storage,modeling of water quality, optimal operation, reliability of water distribution systems, andmany other subjects Some of this information is dispersed in professional and scientific

journals and reports Within the Handbook the various authors have synthesized this

accu-mulated knowledge and presented it in a concise and accessible form

There are obviously many other topics that could have been covered, making the

Handbook even more comprehensive; however, I had to make choices on the coverage These choices obviously reflect my vision of what is needed most in the Handbook The

topics covered are the ones that I feel are the most important for state-of-the art design,analysis, modeling, and operation of water distribution systems The detail of each topic

is fairly well balanced among the chapters and among the topics in each chapter There

is also a reflection of my perspective on the subject, with the constraint that all the rial fits within one handbook Hopefully, the readers will have an understanding and

mate-appreciation of what is being accomplished in this Handbook.

First and foremost this handbook is intended to be a reference for those wishing to

expand their knowledge of water distribution systems The Handbook will be of value to

engineers, managers, operators, and analysts involved with the design, analysis, operation,maintenance, and rehabilitation of water distribution systems This handbook can also behttp://www.nuoc.com.vn

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a valuable reference, if not the text in both undergraduate and graduate courses for ing the design and analysis of water distribution systems.

teach-Each of the authors is a leading expert in the field of water distribution systems Theyhave published extensively in the literature on water distribution systems, and many ofthem have had extensive experience in the design, operation, and analysis of distributionssystems Each of the authors was chosen because of their proven knowledge in the spe-cific area of contribution

As editor in chief of the Handbook, I felt that it was important to provide a brief

his-torical perspective (Chapter 1) of the knowledge of water distribution, starting from theancient times to the present This historical perspective begins with the pressurized waterdistribution systems at Knossos (circa 2000 BC) and provides examples of other ancientwater systems The developments during the 19th and 20th centuries are particularlyimportant to understand our present status at the start of year 2000 with this handbook inplace To better understand where we are and where we may be going, it is wise to look

at where we have been

In 1952 Albert Einstein was offered the presidency of Israel but declined because hethought he was too naive in politics Perhaps his real reason, according to Stephen W

Hawking (A Brief History of Time), was different To quote Einstein, "Equations are more

important to me, because politics is for the present, but an equation is something for nity." Hopefully, this handbook is not only for the present, but also will be a contributionfor the future

eter-Each book that I have worked on has been a part of my lifelong journey in water

resources The Handbook certainly is no exception I have gained more from this

experi-ence than can ever be measured in words

I dedicate this handbook to humanity and human welfare

Larry W MaysScottsdale, Arizona

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I must first acknowledge the authors who made this handbook possible It has been a cere privilege to have worked with such an excellent group of dedicated people They areall experienced professionals who are among the leading experts in their fields.References to material in this handbook should be attributed to the respective chapterauthors

sin-During the past twenty-three years of my academic career as a professor, I have receivedhelp and encouragement from so many people that it is not possible to name them all.These people represent a wide range of universities, research institutions, governmentagencies, and professions To all of you I express my deepest thanks

I would like to acknowledge Arizona State University, especially the time afforded me topursue this handbook

I sincerely appreciate the advice and encouragement of Larry Hager of McGraw-Hillthroughout this project Larry has always been a great guy to work with on the three hand-books that we have done together He is always a joy to talk to, as he's one of the few that

is willing to listen to my fly fishing and snow skiing experiences

This handbook has been a part of a personal journey that began years ago when I was ayoung boy with a love of water Books are companions along the journey of learning Ihope that you will be able to use this handbook in your own journey of learning aboutwater Have a happy and wonderful journey

Larry W Mays

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ABOUT THE EDITOR

Larry W Mays is professor of civil and environmental engineering at Arizona State

University and former chair of the department He was formerly director of the Center forResearch in Water Resources at the University of Texas at Austin, where he also held anEngineering Foundation Endowed Profesorship A registered professional engineer in sevenstates and a registered professional hydrologist, he has served as a consultant to many organi-

zations A widely published expert on water resources, he wrote Optimal Control of Hydrosystems (Marcel Dekker) and was editor in chief of both Water Resources Handbook (McGraw-Hill) and Hydraulic Design Handbook (McGraw-Hill) Co-author of both Applied Hydrology and Hydrosystems Engineering and Management published by McGraw-Hill and was the editor in chief of Reliability Analysis of Water Distribution Systems (ASCE), and co-editor of Computer Modeling of Free-Surface and Pressurized Flows (Kluwer Academic Publishers) He has published extensively on his research in

water resources management

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v

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Contents

Contributors xx

Preface xxi

Acknowledgments xxiii

About the Editor xxiv

1 Introduction 1.1

1.1 Background 1.1 1.2 Historical Aspects of Water Distribution 1.3 1.2.1 Ancient Urban Water Supplies 1.3 1.2.2 Status of Water Distribution Systems in

the 19th Century 1.9 1.2.3 Perspectives on Water Distribution Mains

in the United States 1.10 1.2.4 Early Pipe Flow Computational Methods 1.16 1.3 Modern Water Distribution Systems 1.16 1.3.1 The Overall Systems 1.16 1.3.2 System Components 1.20 1.3.3 System Operation 1.26 1.3.4 The Future 1.29 References 1.30

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2 Hydraulics of Pressurized Flow 2.1

2.1 Introduction 2.1 2.2 Importance of Pipeline Systems 2.2 2.3 Numerical Models: Basis for Pipeline Analysis 2.3 2.4 Modeling Approach 2.4 2.4.1 Properties of Matter (What?) 2.5 2.4.2 Laws of Conservation (How?) 2.6 2.4.3 Conservation of Mass 2.7

Species 2.7 2.4.3.2 Steady Flow 2.8 2.4.4 Newton's Second Law 2.9 2.5 System Capacity: Problems in Time and Space 2.10 2.6 Steady Flow 2.13 2.6.1 Turbulent Flow 2.15 2.6.2 Headless Caused by Friction 2.16 2.6.3 Comparison of Loss Relations 2.18 2.6.4 Local Losses 2.21 2.6.5 Tractive Force 2.22 2.6.6 Conveyance System Calculations: Steady

Uniform Flow 2.23 2.6.7 Pumps: Adding Energy to the Flow 2.26 2.6.8 Sample Application Including Pumps 2.28 2.6.9 Networks - Linking Demand and Supply 2.30 2.7 Quasi-Steady Flow: System Operation 2.30 2.8 Unsteady Flow: Introduction of Fluid Transients 2.32 2.8.1 Importance of Waterhammer 2.32 2.8.2 Cause of Transients 2.34

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2.8.3 Physical Nature of Transient Flow 2.35

2.8.6.1 Gate Discharge Equation 2.40

2.8.6.3 Pressure Regulating Valves 2.42 2.8.7 Conclusion 2.42 References 2.42

3 System Design: An Overview 3.1

3.1 Introduction 3.1 3.1.1 Overview 3.1 3.1.2 Definitions 3.2 3.2 Distribution System Planning 3.2 3.2.1 Water Demands 3.2 3.2.2 Planning and Design Criteria 3.7

3.2.2.1 Supply 3.7 3.2.2.2 Storage 3.7 3.2.2.3 Fire Demands 3.8 3.2.2.4 Distribution System Analysis 3.8 3.2.2.5 Service Pressures 3.8 3.2.3 Peaking Coefficients 3.9

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3.2.4 Computer Models and System Modeling 3.9

3.2.4.1 History of Computer Models 3.10 3.2.4.2 Software Packages 3.10

Model 3.11 3.3 Pipeline Preliminary Design 3.11 3.3.1 Alignment 3.11 3.3.2 Subsurface Conflicts 3.13 3.3.3 Rights-of-Way 3.13 3.4 Piping Materials 3.13 3.4.1 Ductile Iron Pipe (DIP) 3.14

3.4.1.1 Materials 3.14

Thicknesses 3.14 3.4.1.3 Joints 3.14 3.4.1.4 Gaskets 3.14 3.4.1.5 Fittings 3.14 3.4.1.6 Linings 3.16 3.4.1.7 Coatings 3.17 3.4.2 Polyvinyl Chloride (PVC) Pipe 3.18

Thicknesses 3.19 3.4.2.3 Joints 3.19 3.4.2.4 Gaskets 3.20 3.4.2.5 Fittings 3.20 3.4.2.6 Linings and Coatings 3.20 3.4.3 Steel Pipe 3.21

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Thicknesses 3.21 3.4.3.3 Joints 3.22 3.4.3.4 Gaskets 3.22 3.4.3.5 Fittings 3.22 3.4.3.6 Linings and Coatings 3.23 3.4.4 Reinforced Concrete Pressure Pipe

AWWA C300 3.28 3.4.5 High-Density Polyethylene (HDPE) Pipe 3.29

Thicknesses 3.30 3.4.5.3 Joints 3.30 3.4.5.4 Gaskets 3.31 3.4.5.5 Fittings 3.31 3.4.5.6 Linings and Coatings 3.31 3.4.6 Asbestos-Cement Pipe (ACP) 3.31

Thicknesses 3.31 3.4.6.2 Joints and Fittings 3.32 3.4.7 Pipe Material Selection 3.32 3.5 Pipeline Design 3.34 3.5.1 Internal Pressures 3.34

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3.5.2 Loads on Buried Pipe 3.34

3.5.2.1 Earth Loads 3.35 3.5.2.2 Rigid Pipe 3.36 3.5.2.3 Flexible Pipe 3.37 3.5.3 Thrust Restraint 3.38

3.5.3.1 Thrust Blocks 3.39 3.5.3.2 Restrained Joints 3.41 3.6 Distribution and Transmission System Valves 3.44 3.6.1 Isolation Valves 3.44

3.6.1.1 Gate Valves 3.45 3.6.1.2 Butterfly Valves 3.45 3.6.2 Control Valves 3.46

3.6.2.1 Pressure-Reducing Valve 3.46 3.6.2.2 Pressure-Sustaining Valves 3.47 3.6.2.3 Flow-Control Valves 3.47 3.6.2.4 Altitude Valves 3.47 3.6.2.5 Pressure-Relief Valves 3.47 3.6.3 Blow-offs 3.47 3.6.4 Air Release and Vacuum-Relief Valves 3.48 References 3.48

4 Hydraulics of Water Distribution Systems 4.1

4.1 Introduction 4.1 4.1.1 Configuration and Components of Water

Distribution Systems 4.1 4.1.2 Conservation Equations for Pipe

Systems 4.3 4.1.3 Network Components 4.3 4.2 Steady-State Hydraulic Analysis 4.5 4.2.1 Series and Parallel Pipe Systems 4.5

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4.2.2 Branching Pipe Systems 4.7 4.2.3 Pipe Networks 4.11

4.2.3.1 Hardy Cross Method 4.11 4.2.3.2 Linear Theory Method 4.17

the Node Equations 4.18 4.2.3.4 Gradient Algorithm 4.20

Methods 4.22 4.2.3.6 Extended-Period Simulation 4.23 4.3 Unsteady Flow in Pipe Network Analysis 4.24 4.3.1 Governing Equations 4.24 4.3.2 Solution Methods 4.25

4.3.2.1 Loop Formulation 4.25

Algorithm 4.26 4.4 Computer Modeling of Water Distribution Systems 4.26 4.4.1 Applications of Models 4.27 4.4.2 Model Calibration 4.27 References 4.28

5 Pump System Hydraulic Design 5.1

5.1 Pump Types and Definitions 5.1 5.1.1 Pump Standards 5.1 5.1.2 Pump Definitions and Terminology 5.2 5.1.3 Types of Centrifugal Pumps 5.6 5.2 Pump Hydraulics 5.8 5.2.1 Pump Performance Curves 5.8 5.2.2 Pipeline Hydraulics and System Curves 5.8

5.2.2.1 Hazen-Williams Equation 5.8

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5.2.2.2 Manning's Equation 5.11 5.2.2.3 Darcy-Weisbach Equation 5.11 5.2.2.4 Comparisons of f, C, and n 5.12 5.2.3 Hydraulics of Valves 5.12 5.2.4 Determination of Pump Operating Points-

Single Pump 5.13 5.2.5 Pumps Operating in Parallel 5.13 5.2.6 Variable-Speed Pumps 5.13 5.3 Concept of Specific Speed 5.18 5.3.1 Introduction: Discharge-Specific Speed 5.18 5.3.2 Suction-Specific Speed 5.19 5.4 Net Positive Suction Head 5.19 5.4.1 Net Positive Suction Head Available 5.19 5.4.2 Net Positive Suction Head Required by a

Pump 5.20 5.4.3 NPSH Margin or Safety Factor

Considerations 5.22 5.4.4 Cavitation 5.22 5.5 Corrected Pump Curves 5.22 5.6 Hydraulic Considerations in Pump Selection 5.27 5.6.1 Row Range of Centrifugal Pumps 5.27 5.6.2 Causes and Effects of Centrifugal Pumps

Operating Outside Allowable Flow Ranges 5.28 5.6.3 Summary of Pump Selection 5.28 5.7 Application of Pump Hydraulic Analysis to Design of

Pumping Station Components 5.30 5.7.1 Pump Hydraulic Selections and

Specifications 5.30 5.7.1.1 Pump Operating Ranges 5.30

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Operating Problems 5.32 5.7.2 Piping 5.32

Piping Installation Guidelines 5.33 5.7.2.2 Fluid Velocity 5.33

Station Design 5.35 5.8.1 Effect of Surge on Valve Selection 5.35 5.8.2 Effect of Surge on Pipe Material

Selection 5.36 References 5.36 Appendix 5.37

6 Hydraulic Transient Design for Pipeline

Systems 6.1

6.1 Introduction to Waterhammer and Surging 6.1

6.2.1 Definitions 6.2 6.2.2 Acoustic Velocity 6.2 6.2.3 Joukowsky (Waterhammer) Equation 6.3 6.3 Hydraulic Characteristics of Valves 6.4 6.3.1 Descriptions of Various Types of Valves 6.5

Valves 6.6

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6.3.3 Definition of Hydraulic Performance of

Valves 6.6

Characteristics 6.8 6.3.5 Valve Operation 6.9 6.4 Hydraulic Characteristics of Pumps 6.9 6.4.1 Definition of Pump Characteristics 6.10 6.4.2 Homologous (Affinity) Laws 6.10

Characteristics 6.12 6.4.4 Representation of Pump Data for

Numerical Analysis 6.15 6.4.5 Critical Data Required for Hydraulic

Analysis of Systems with Pumps 6.16 6.5 Surge Protection and Surge Control Devices 6.18 6.5.1 Critical Parameters for Transients 6.18 6.5.2 Critique of Surge Protection 6.20 6.5.3 Surge Protection Control and Devices 6.22 6.6 Design Considerations 6.24 6.7 Negative Pressures and Water Column Separation

in Networks 6.26 6.8 Time Constants for Hydraulic Systems 6.27 6.9 Case Studies 6.27 6.9.1 Case Study with One-Way and Simple

Surge Tanks 6.27 6.9.2 Case Study with Air Chamber 6.28 6.9.3 Case Study with Air-Vacuum Breaker 6.31 References 6.32

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Contents xv

7 Optimal Design of Water Distribution Systems 7.1

7.1 Overview 7.1 7.2 Problem Definition 7.1 7.3 Mathematical Formulation 7.3 7.4 Optimization Methods 7.4 7.4.1 Branched Systems 7.4 7.4.2 Looped Pipe Systems via Linearization 7.5 7.4.3 General System Design via Nonlinear

Programming 7.7 7.4.4 Stochastic Search Techniques 7.8 7.5 Applications 7.9 7.6 Summary 7.12 References 7.13

8 Water-Quality Aspects of Construction and

Operations 8.1

8.1 Introduction 8.1 8.2 Disinfection of New Water Mains 8.1 8.2.1 Need for Disinfection 8.2 8.2.2 Disinfection Chemicals 8.2 8.2.3 Disinfection Procedures 8.2

8.2.3.1 The Tablet Method 8.2

8.2.3.3 The Slug Method 8.3 8.2.4 Testing New Mains 8.3 8.2.5 Main Repairs 8.3 8.2.6 Disposal of Highly Chlorinated Water 8.3 8.3 Disinfection of Storage Tanks 8.4 8.3.1 Disinfection Procedures for Filling Tanks 8.4

8.3.1.1 Method 1 8.4

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8.3.1.2 Method 2 8.4 8.3.1.3 Method 3 8.5 8.3.2 Underwater Inspection 8.5 8.4 Cross-Connection Control 8.5 8.4.1 Definitions 8.5 8.4.2 Cross-Connection Control Programs 8.5 8.4.3 Backflow Prevention 8.6

8.4.3.1 Air Gap 8.6

Preventers and Double-Check Valve Assemblies 8.6

Vacuum Breakers, and Barometric Loops 8.6

8.4.4 Application of Backflow Preventers 8.7 8.5 Flushing of Distribution Systems 8.8 8.5.1 Background 8.8 8.5.2 Flushing Procedures 8.8 8.5.3 Directional Flushing 8.9 8.5.4 Alternating of Disinfectants 8.9 References 8.10

9 Water Quality 9.1

9.1 Introduction 9.1 9.1.1 Overview 9.1 9.1.2 Definitions 9.2 9.2 Water-Quality Processes 9.3 9.2.1 Loss of Disinfectant Residual 9.3

9.2.1.1 Disinfection Methods 9.4

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9.2.1.2 Rates of Disinfectant Loss 9.5 9.2.1.3 Mitigation of Disinfectant Loss 9.5 9.2.2 Growth of Disinfection By-Products 9.6 9.2.3 Internal Corrosion 9.6

9.2.3.1 Types of Corrosion 9.7 9.2.3.2 Factors Affecting Corrosion 9.7 9.2.3.3 Indicators of Corrosion 9.8 9.2.3.4 Control of Corrosion 9.8 9.2.4 Biofilms 9.9

9.2.4.1 Origins 9.9 9.2.4.2 Composition 9.9 9.2.4.3 Significance 9.10 9.2.4.4 Treatment and Control 9.10 9.3 Water-Quality Monitoring 9.11 9.3.1 Routine Monitoring 9.11

9.3.1.1 Regulatory Requirements 9.11 9.3.1.2 Sampling Methods 9.11 9.3.1.3 Sampling Parameters 9.11 9.3.2 Synoptic Monitoring 9.11 9.4 Water-Quality Modeling 9.15 9.4.1 History 9.16 9.4.2 Governing Equations 9.16

9.4.2.1 Adjective Transport in Pipes 9.17 9.4.2.2 Mixing at Pipe Junctions 9.17 9.4.2.3 Mixing in Storage Facilities 9.17 9.4.2.4 Bulk Flow Reactions 9.17 9.4.2.5 Pipe Wall Reactions 9.18 9.4.2.6 System of Equations 9.18 9.4.3 Solution Methods 9.18

9.4.3.1 Steady-State Models 9.18

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9.4.3.2 Dynamic Models 9.19 9.4.4 Data Requirements 9.20

9.4.4.1 Hydraulic Data 9.20 9.4.4.2 Water-Quality Data 9.20 9.4.4.3 Reaction-Rate Data 9.20 9.4.5 Model Calibration 9.21

Substances 9.21

Substances 9.21 9.4.5.3 Uses for Hydraulic Calibration 9.21 References 9.22

10 Hydraulic Design of Water Distribution Storage

Tanks 10.1

10.1 Introduction 10.1 10.2 Basic Concepts 10.1 10.2.1 Equalization 10.2 10.2.2 Pressure Maintenance 10.2 10.2.3 Fire Storage 10.2 10.2.4 Emergency Storage 10.2 10.2.5 Energy Consumption 10.3 10.2.6 Water Quality 10.3 10.2.7 Hydraulic Transient Control 10.3 10.2.8 Aesthetics 10.4 10.3 Design Issues 10.4 10.3.1 Floating Versus Pumped Storage 10.4 10.3.2 Ground Versus Elevated Tank 10.5 10.3.3 Effective Versus Total Storage 10.6 10.3.4 Private Versus Utility Owned Tanks 10.6

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10.3.5 Pressurized Tanks 10.6 10.4 Location 10.7 10.4.1 Clearwell Storage 10.7 10.4.2 Tanks Downstream of the Demand

Center 10.8 10.4.3 Multiple Tanks in the Pressure Zone 10.8 10.4.4 Multiple Pressure-Zone Systems 10.9 10.4.5 Other Sitting Considerations 10.9 10.5 Tank Levels 10.9 10.5.1 Setting Tank Overflow Levels 10.9 10.5.2 Identifying Tank Service Areas 10.10 10.5.3 Identifying Pressure Zones 10.10 10.6 Tank Volume 10.11 10.6.1 Trade-offs in Tank Volume Design 10.11 10.6.2 Standards-Driven Sizing 10.12 10.6.3 Functional Design 10.12

10.6.3.1 Equalization Storage 10.12 10.6.3.2 Fire Storage 10.14 10.6.3.3 Emergency Storage 10.16 10.6.3.4 Combination Equalization, Fire

and Emergency Storage 10.16 10.6.3.5 Summary of Functional Sizing 10.16 10.6.4 Staging Requirements 10.16 10.6.5 Useful Dead Storage 10.17 10.7 Other Design Considerations 10.18 10.7.1 Altitude Valves 10.18 10.7.2 Cathodic Protection and Coatings 10.18 10.7.3 Overflows and Vents 10.18 References 10.19

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11 Quality of Water in Storage 11.1

11.1 Introduction 11.1 11.1.1 Overview 11.1 11.1.2 Definitions 11.2 11.2 Water Quality Problems 11.2 11.2.1 Chemical Problems 11.2

11.2.1.1 Loss of Disinfectant Residual 11.2 11.2.1.2 Formation of Disinfection By-

Products 11.3 11.2.1.3 Development of Taste and

Odor 11.3 11.2.1.4 Increase in pH 11.4 11.2.1.5 Corrosion 11.4 11.2.1.6 Buildup of Iron and Manganese 11.4

Sulfide 11.5 11.2.1.8 Leachate from Internal

Coatings 11.5 11.2.2 Microbiological Problems 11.5

11.2.2.1 Bacterial Regrowth 11.5 11.2.2.2 Nitrification 11.6 11.2.2.3 Worms and Insects 11.6 11.2.3 Physical Problems 11.7

11.2.3.1 Sediment Buildup 11.7 11.2.3.2 Entry of Contaminants 11.7 11.2.3.3 Temperature 11.8 11.3 Mixing and Aging in Storage Facilities 11.8 11.3.1 Ideal Flow Regimes 11.8 11.3.2 Jet Mixing 11.9 11.3.3 Mixing Times 11.9

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Contents xxi

11.3.4 Stratification 11.10 11.3.5 Aging 11.11 11.4 Monitoring and Sampling 11.12 11.4.1 Routine Monitoring 11.12

11.4.1.1 Typical Parameters of Water

Quality 11.13 11.4.1.2 Parameters of Nitrification

Monitoring 11.13 11.4.1.3 Parameters of Sediment

Monitoring 11.13 11.4.1.4 Parameters of Biofilm

Monitoring 11.17 11.4.2 Sampling Methods and Equipment 11.17 11.4.3 Monitoring Frequency and Location of

Samples 11.18 11.4.4 Special Studies 11.20

11.4.4.1 Intensive Studies of Water

Quality and Tracers 11.20 11.4.4.2 Temperature Monitoring 11.20 11.5 Modeling 11.22 11.5.1 Scale Models 11.22

11.5.1.1 Principles of Similitude 11.22 11.5.1.2 Construction of a Model 11.23 11.5.1.3 Types of Tracers 11.24 11.5.1.4 Temperature Modeling 11.25 11.5.2 Computational Fluid Dynamics 11.25

11.5.2.1 Mathematical Formulations of

CFD Models 11.26 11.5.2.2 Application of CFD Models 11.27 11.5.3 Systems Models 11.28

11.5.3.1 Background 11.28

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11.5.3.2 Elemental Systems Models 11.28 11.5.3.3 Compartment Models 11.28 11.5.3.4 Application of Systems Models 11.28 11.6 Design and Operational Issues 11.30 11.6.1 Water-Quality Design Objectives 11.30 11.6.2 Modes of Operation: Simultaneous Inflow-

Outflow Versus Fill and Draw 11.30 11.6.3 Flow Regimes: Complete Mix Versus Plug

Flow 11.30 11.6.3.1 Effects of Flow Regime on Loss

of Disinfectant in Reservoirs 11.31 11.6.3.2 Mixed Flow 11.31 11.6.3.3 Plug Flow 11.32 11.6.3.4 Recommendations 11.33 11.6.4 Stratification in Reservoirs 11.33 11.7 Inspection and Maintenance Issues 11.34 11.7.1 Inspections 11.34 11.7.2 Maintenance 11.35 References 11.36

12 Computer Models/EPANET 12.1

12.1 Introduction 12.1 12.1.1 Need for Computer Models 12.1 12.1.2 Uses of Computer Models 12.2 12.1.3 History of Computer Models 12.2 12.2 Use of a Computer Model 12.3 12.2.1 Network Representation 12.3

12.2.1.1 Network Components 12.3 12.2.1.2 Network Skeletonization 12.4

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Contents xxiii

12.2.2 Compilation of Data 12.4

12.2.2.1 ID Labels 12.5 12.2.2.2 Nodal Elevations 12.5 12.2.2.3 Pipe Diameters 12.5 12.2.2.4 Pipe Roughness 12.6 12.2.2.5 Pump Curves 12.6 12.2.3 Estimation of Demand 12.6 12.2.4 Operating Characteristics 12.7 12.2.5 Reaction-Rate Information 12.7 12.2.6 Model Calibration 12.8 12.3 Computer Model Internals 12.8 12.3.1 Input Processing 12.9 12.3.2 Topological Processing 12.9 12.3.3 Hydraulic Solution Algorithms 12.9 12.3.4 Linear-Equation Solver 12.11 12.3.5 Extended-Period Solver 12.11 12.3.6 Water-Quality Algorithms 12.12 12.3.7 Output Processing 12.12 12.4 EPANET Program 12.13 12.4.1 Background 12.13 12.4.2 Program Features 12.14 12.4.3 User Interface 12.15 12.4.4 Solver Module 12.17 12.4.5 Programmer's Toolkit 12.20 12.5 Conclusion 12.20 References 12.21

13 Water Quality Modeling-Case Studies 13.1

13.1 Introduction 13.1

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xxiv Contents

13.2 Design of Distribution Systems in the United

States 13.2 13.3 Water Quality in Networks 13.3 13.4 Hydraulic and Water-Quality Models 13.4 13.4.1 Steady-State-Water Quality Models 13.5 13.4.2 Dynamic Water-Quality Models 13.5 13.5 Early Applications of Water-Quality Modeling 13.6 13.5.1 North Penn Study 13.6

13.5.1.1 Network Modeling 13.7 13.5.1.2 Variations in Water Quality

Data 13.8 13.5.1.3 Development of Dynamic Water-

Quality Algoritm 13.8 13.5.2 South Central Connecticut Regional Water

Authority 13.9 13.5.2.1 System Modeling 13.13 13.5.2.2 Design of the Field Study 13.13 13.5.2.3 Results from the Field Study 13.13 13.5.2.4 Verification Study 13.17 13.5.2.5 Presampling Procedures 13.17 13.5.2.6 Analysis of Sampling Results 13.17 13.5.2.7 Modeling of Chlorine Residual 13.21 13.5.3 Case Study of Cabool, Missouri 13.22 13.6 Evolution of Water Quality Modeling 13.22 13.7 Modeling Propagation of Contaminants 13.23 13.7.1 Case Study of the North Marin Water

District 13.24 13.7.1.1 Water-Quality Study 13.29 13.7.1.2 Modeling of Total

Trihalomethane Formations 13.30

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Contents xxv

13.7.1.3 Chlorine Demand 13.34 13.7.1.4 Effect of System Demand 13.34 13.7.2 Complement to the North Marin study 13.34 13.7.3 Waterborne Outbreak in Gideon,

Missouri 13.36 13.7.3.1 Description of the System 13.38 13.7.3.2 Identification of the Outbreak 13.39 13.7.3.3 Possible Causes 13.40 13.7.3.4 Evaluation of the System 13.41 13.7.3.5 Performance of the System 13.41 13.7.3.6 Propagation of the Contaminant 13.43 13.8 Current Trends in Water-Quality Modeling 13.44 13.8.1 Study in Cholet, France 13.44 13.8.2 Case Study in Southington, Connecticut 13.44 13.8.3 Mixing in Storage Tanks 13.45 13.9 Summary and Conclusions 13.45 References 13.46

14 Calibration of Hydraulic Network Models 14.1

14.1 Introduction 14.1 14.1.1 Network Characterization 14.1 14.1.2 Network Data Requirements 14.1 14.1.3 Model Parameters 14.3 14.2 Identify the Intended Use of the Model 14.3 14.3 Determine Estimates of the Model Parameters 14.3 14.3.1 Pipe Roughness Values 14.4

14.3.1.1 Chart the Pipe Roughness 14.4 14.3.1.2 Field Test the Pipe Roughness 14.6 14.3.2 Distribution of Nodal Demands 14.9

14.3.2.1 Spatial Distribution of Demands 14.10

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xxvi Contents

14.3.2.2 Temporal Distribution of

Demands 14.12 14.4 Collect Calibration Data 14.12 14.4.1 Fire-Flow Tests 14.12 14.4.2 Telemetric Data 14.13 14.4.3 Water-Quality Data 14.14 14.5 Evaluate the Results of the Model 14.14 14.6 Perform a Macro-Level Calibration of the Model 14.15 14.7 Perform a Sensitivity Analysis 14.16 14.8 Perform a Macro-Level Calibration of the Model 14.16 14.8.1 Analytical Approaches 14.17 14.8.2 Simulation Approaches 14.17 14.8.3 Optimization Approaches 14.17 14.9 Future Trends 14.21 14.10 Summary and Conclusion 14.21 References 14.21

15 Operation of Water Distribution Systems 15.1

15.1 Introduction 15.1 15.2 How Systems Are Operated 15.2 15.2.1 Typical Operating Indexes 15.2 15.2.2 Operating Criteria 15.3 15.2.3 Water Quality and Operations 15.4 15.2.4 Emergency Operations 15.4 15.3 Monitoring of System Performance with SCADA

Systems 15.5 15.3.1 Anatomy of a SCADA System 15.6 15.3.2 Data Archiving 15.9

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Contents xxvii

15.4 Control of Water Distribution System 15.9 15.4.1 Control Strategies 15.10

15.4.1.1 Supervisory Control 15.10 15.4.1.2 Automatic Control 15.10 15.4.1.3 Advanced Control 15.10 15.4.2 Centralized Versus Local Control 15.11 15.5 Linking of SCADA Systems with Analysis and

Control Models 15.11 15.5.1 Data Requirements of Analysis and

Control Models 15.12 15.5.2 Establishment of the Link 15.13 15.6 Use of Central Databases in System Control 15.15 15.7 What the Future Holds 15.16 References 15.16

16 Optimization Models for Operations 16.1

16.1 Introduction 16.1 16.2 Formulations for Minimizing Energy Cost

Minimization 16.3 16.2.1 Energy Management 16.3 16.2.2 Management Strategies 16.3 16.2.3 Management Models 16.5

16.2.3.1 Hydraulic Network Models 16.5 16.2.3.2 Demand Forecast Models 16.7 16.2.3.3 Control Models 16.8 16.2.4 Optimization Models 16.9

16.2.4.1 Problem Formulation 16.9 16.2.4.2 System Classification 16.10 16.2.5 Summary and Conclusions 16.14 16.3 Formulations to Satisfy Water Quality 16.16

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xxviii Contents

16.4 Solution Methods and Applications for

Water-Quality Purposes 16.19 16.4.1 Mathematical Programming Approach 16.19 16.4.2 Simulated Annealing Approach 16.22 16.4.3 Development of Cost Function 16.24 16.4.4 Sample Application 16.26 16.4.5 Advantages and Disadvantages of the

Two Methods 16.28 16.5 Optimal Scheduling of Booster Disinfection 16.28 16.5.1 Background 1: Linear Superposition 16.33 16.5.2 Background 2: Dynamic Network Water-

Quality Models in a Planning Context 16.34 16.5.3 Optimal Scheduling of Booster-Station

Dosages as Linear Programming Problem 16.36 16.5.4 Optimal Location and Scheduling of

Booster-Station Dosage as a Integer Linear Programming Problem 16.36 16.5.5 Optimal Location of Booster Stations as a

Mixed-Maximum Set-Covering Problem 16.38 16.5.6 Solution of the Optimization Models 16.40 16.5.7 Available Software 16.41 16.5.8 Summary 16.42 References 16.43

17 Maintenance and Rehabilitation/Replacement 17.1

17.1 Introduction 17.1 17.1.1 Maintenance and Rehabilitation

Problems 17.1 17.1.1.1 Normal Wear 17.1

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Contents xxix

17.1.1.2 Corrosion 17.2 17.1.1.3 Unforeseen Loads 17.2 17.1.1.4 Poor Manufacture and

Installation 17.2 17.1.2 Preview of the Chapter 17.2 17.2 Unaccounted-for Water 17.2 17.2.1 Indicators for Unaccounted-for Water 17.3 17.2.2 Understanding the Causes of

Unaccounted-for Water 17.3 17.2.3 Components of Unaccounted-for Water 17.5

17.2.3.1 Water Main Leakage 17.5 17.2.3.2 Service Pipe Leakage 17.7 17.2.3.3 System Pressure 17.7 17.2.3.4 Fire Fighting 17.7 17.2.3.5 Main Flushing 17.8 17.2.3.6 Blowoffs 17.8 17.2.3.7 Flat rate Customers 17.8

17.2.3.9 Meter under Registration 17.8 17.2.3.10 Theft of Water 17.9 17.2.4 Summary 17.9 17.3 Pipe Breaks 17.10 17.3.1 Corrosion 17.10

17.3.1.1 External Soil Corrosion 17.10 17.3.1.2 Internal Corrosion 17.11 17.3.1.3 Stray Current Corrosion 17.11 17.3.1.4 Bimetallic Connections 17.11 17.3.2 External Loads 17.11 17.3.3 Poor Tapping 17.13 17.3.4 Pressure-Related Breaks 17.13

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xxx Contents

17.3.5 Repair Versus Replacement 17.14 17.4 Hydraulic Carrying Capacity 17.16 17.4.1 Diagnosis of Pressure Problems 17.16

17.4.1.1 Pressure Gauges 17.16 17.4.1.2 Hydraulic Modeling 17.16 17.4.2 Correction of Pressure Problems 17.17

17.4.2.1 Closed Isolating Valves 17.17 17.4.2.2 Elevation and Pressure Zone

Issues 17.18 17.4.2.3 Carrying Capacity 17.18 17.4.2.4 Inadequate Capacity 17.19 17.4.3 Pipe Rehabilitation Technology 17.20 17.4.4 Evaluation of Pipe Rehabilitation 17.21 17.5 Maintenance Information Systems 17.21 17.5.1 System Mapping 17.22 17.5.2 System Database 17.22 17.5.3 Geographic Information Systems 17.22 17.5.4 Maintenance Management Systems 17.23 17.5.5 SCADA Systems 17.23 References 17.24

18 Reliability Analysis for Design 18.1

18.1 Failure Modes for Water Distribution Systems 18.1 18.1.1 Need and Justification 18.1 18.1.2 Definitions of Distribution System

Repairs 18.3 18.1.3 Failure Modes 18.4

18.1.3.1 Performance Failure 18.4

Failure 18.5

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Contents xxxi

18.1.4 Reliability: Indexes and Approaches 18.5 18.2 Practical Aspects of Providing Reliability 18.6 18.2.1 Improving the Reliability of Water

Distribution Systems 18.6 18.2.1.1 Piping Materials 18.6 18.2.1.2 Construction Methods 18.7 18.2.1.3 Pipe Sizing 18.7 18.2.1.4 Looped Water Distribution

System 18.7 18.2.1.5 Emergency Storage 18.8 18.2.1.6 Backup Pumping and Control

Valves 18.8 18.2.1.7 Standby Power 18.8 18.2.1.8 Emergency Controls 18.8

18.2.1.10 Water Distribution System

Modeling 18.9 18.2.1.11 Transient Analysis 18.9 18.2.1.12 Operational Considerations 18.9 18.2.1.13 Maintenance Considerations 18.10 18.2.2 Analyzing the Effect of Valving on System

Reliability 18.10 18.2.2.1 Background 18.10 18.2.2.2 Diagrams of Distribution

Segments 18.10 18.2.2.3 Loops Served from Transmission

Mains 18.11 18.2.2.4 Emergency Interconnections 18.11 18.2.2.5 Transmission lines Connected to

Old Systems 18.13 18.2.2.6 Typical Cross-Intersections 18.13

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xxxii Contents

18.2.2.7 Application of Segments in Valve

Locations and Reliability Evaluation 18.14 18.3 Component Reliability Analysis 18.15 18.3.1 Failure Density, Failure Rate, and Mean

Time to Failure 18.15 18.3.2 Availability and Unavailability 18.19 18.4 Review of Models Fore Reliability of Water

Distribution Systems 18.22 18.4.1 Reliability of a System Failure 18.22 18.4.2 Failure Modes 18.23 18.4.3 Approaches to the Assessment of

Reliability 18.26 18.4.4 Models and Techniques for Assessing

Network Reliability 18.29 18.4.4.1 Simulation Models 18.29 18.4.4.2 Analytical Approaches 18.33 18.4.4.3 Heuristic Techniques 18.39 18.4.4.4 Redundancy Based Measures 18.39 18.4.5 Overview of Reliability Measures 18.40 18.4.6 Observations 18.42 18.5 Measure of Link Importance 18.43 References 18.49

Index I.1

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CHAPTER 1

INTRODUCTION

Larry W Mays

Department of Civil and Environmental Engineering

Arizona State University Tempe, AZ

Because of the importance of safe drinking water for the needs of society and forindustrial growth, considerable emphasis recently has been given to the condition of theinfrastructure Large capital expenditures will be needed to bring the concerned systems

to higher levels of serviceability and to lend vigor to U.S industry and help it remain petitive in the world economy One of the most vital services to industrial growth is anadequate water supply system—without it, industry cannot survive

com-The lack of adequate water supply systems is due to both the deterioration of agingwater supplies in older urbanized areas and to the nonexistence of water supply systems

in many areas that are undergoing rapid urbanization, such as in the southwestern UnitedStates In other words, methods for evaluation of the nation's water supply services need

to consider not only rehabilitation of existing urban water supply systems but also thefuture development of new water supply systems to serve expanding population centers.Both the adaptation of existing technologies and the development of new innovative tech-nologies will be required to improve the efficiency and cost-effectiveness of future andexisting water supply systems and facilities necessary for industrial growth

An Environmental Protection Agency (EPA) survey (Clark et al., 1982) of ous water supply projects concluded that the distribution facilities in water supply

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previ-Source: From Gleick (1993).

These data present the drinking water and sanitation service needs in developing countries only and use United Nations population estimates for 2000 The level of service is typically defined by the World Meteorological Organization As used here by the World Health Organization (WHO), safe drinking water includes treated surface water and untreated water from protected springs, boreholes, and wells The WHO defines access to safe drinking water in urban areas as piped water to housing units or to public standpipes within 200 m In rural areas, reason- able access implies that fetching water does not take up a disproportionate part of the day.

systems will account for the largest cost item in future maintenance budgets The aging,deteriorating systems in many areas raise tremendous maintenance decision-making prob-lems, which are further complicated by the expansion of existing systems Deterioration

of the water distribution systems in many areas has translated into a high proportion ofunaccounted-for water caused by leakage Not only does this amount to loss of a valuableresource; it also raises concerns about safe drinking water because of possible contami-nation from cracked pipes

The reliability of the existing aging systems is continually decreasing (Mays, 1989).Only recently have municipalities been willing or able to finance rehabilitation of deteri-orating pipelines, and needed maintenance and replacement of system components is stillbeing deferred until a catastrophe occurs or the magnitude of leakage justifies the expense

of repair Water main failures have been extensive in many cities

As a result of governmental regulations and consumer-oriented expectations, a majorconcern now is the transport and fate of dissolved substances in water distribution systems.The passage of the Safe Drinking Water Act in 1974 and its Amendments in 1986(SDWAA) changed the manner in which water is treated and delivered in the United States.The EPA is required to establish maximum contaminant level (MCL) goals for each cont-aminant that may have an adverse effect on the health of persons These goals are set to thevalues at which no known or expected adverse effects on health can occur By allowing amargin of safety (Clark, 1987), previous regulatory concerns were focused on water as it leftthe treatment plant before entering the distribution system (Clark, 1987), disregarding thevariations in water quality which occurred in the water distribution systems

To understand better where we are and where we may be going, it is sometimes wise

to look at where we have been This is particularly true in water management, whereunderstanding the lessons of the history of water management may provide clues to solv-

TABLE 1.1 Developing Country Needs for Urban and Rural Water Supply and Sanitation,

243 989

1232

377

1364 1741

Expected Population Increase 1990-2000 (W 6 )

570 312 882

Total Additional Population Requiring Service by 2000 (W 6 )

813

1301 2114

947

1676 2623

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ing some of the present-day and future problems The next section is devoted to theaspects of the historical development of water distribution systems.

7.2 HISTORICAL ASPECTS OF WATER DISTRIBUTION

1.2.1 Ancient Urban Water Supplies

Humans have spent most of their history as hunters and food gatherers Only in the last9000-10,000 years have human beings discovered how to raise crops and tame animals.This agricultural revolution probably took place first in the hills to the north of present-day Iraq and Syria From there, the agricultural revolution spread to the Nile and IndusValleys During the time of this agricultural breakthrough, people began to live inpermanent villages instead of leading a wandering existence About 6000-7000 years ago,farming villages of the Near and Middle East became cities The first successful efforts tocontrol the flow of water were made in Mesopotamia and Egypt Remains of these pre-historic irrigation canals still exist Table 1.2 from Crouch (1993) presents a chronology

of water knowledge Crouch (1993) pointed out, traditional water knowledge relied ongeological and meteorological observation plus social consensus and administrative orga-nization, particularly among the ancient Greeks

Knossos, approximately 5 km from Herakleion, the modern capital of Crete, was one ofthe most ancient and unique cities of the Aegean Sea area and of Europe Knossos was firstinhabited shortly after 6000 B.C., and within 3000 years it had became the largest Neolithic(Neolithic Age, ca 5700-28 B.C.) settlement in the Aegean During the Bronze Age(ca 2800-1100 B.C.), the Minoan civilization developed and reached its culmination as thefirst Greek cultural miracle of the Aegean world During the neopalatial period (1700-1400

TABLE 1.2 Chronology of Water Knowledge

Long-distance water supply lines with tunnels and bridges as well as intervention in and harnessing of karstic water systems Public as well as private bathing facilities consisting of: bathtubs or showers, footbaths, washbasins, latrines or toilets, laundry and dishwashing facilities

Utilization of definitely two and probably three qualities of water: potable, subpotable, and nonpotable, including irrigation using storm runoff, probably combined with waste waters Pressure pipes and siphon systems

Source: Crouch (1993).

* Indicates an element discovered, probably forgotten, and rediscovered later.

? Indicates an educated guess.

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B.C.), Knossos was at the height of its splendor The city occupied an area of 75,000-125,000

m2 and had an estimated population on the order of tens of thousands of inhabitants Thewater supply system at Knossos was most interesting An aqueduct supplied water throughtubular conduits from the Knunavoi and Archanes regions and branched out to supply thecity and the palace Figure 1.1 shows the type of pressure conduits used within the palacefor water distribution Unfortunately, around 1450 B.C the Mycenean palace was destroyed

by an earthquake and fire, as were all the palatial cities of Crete

The Acropolis in Athens, Greece, has been a focus of settlement starting in theearliest times Not only its defensive capabilities, but also its water supply made it the log-ical location for groups who dominated the region The location of the Acropolis on anoutcropping of rock, the naturally occurring water, and the ability of the location to savethe rain and spring water resulted in a number of diverse water sources, including cisterns,wells, and springs Figure 1.2 shows the shaft of one archaic water holder at the site of theAcropolis

Anatolia, also called Asia Minor, which is part of the present-day Republic of Turkey,has been the crossroads of many civilizations during the last 10,000 years In this region,there are many remains of ancient water supply systems dating back to the Hittite period(2000-200 B.C.), including pipes, canals, tunnels, inverted siphons, aqueducts, reservoirs,cisterns, and dams

An example of one ancient city with a well-developed water supply system is Ephesus

in Anatolia, Turkey, which was founded during the 10th century B.C as an Ionian city rounding the Artemis temple During the 6th century B.C., Ephesus was reestablished atthe present site, where it further developed during the Roman period Water for the greatfountain, built during 4-14 A.D., was diverted by a small dam at Marnss and was conveyed

sur-to the city by a 6-km-long system consisting of one larger and two smaller clay pipe lines.Figure 1.3 shows the types of clay pipes used at Ephesus for water distribution purposes

FIGURE 1.1 Water distribution pipe at Knossos, Crete (Photograph by L.W Mays).

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FIGURE 1.3 (A, B) Water distribution

pipe in Ephesus, Turkey (Photographs by

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