INTRODUCTION TO URBAN WATER DISTRIBUTION - CHAPTER 1 pdf

This book comprises the training material used in the three-week module ‘Water Transport and Distribution 1’, which is a part of the 18-monthMaster of Science programme in Water Supply E

INTRODUCTION TO URBAN WATER DISTRIBUTION

UNESCO-IHE LECTURE NOTE SERIES

BALKEMA - Proceedings and Monographs

in Engineering, Water and Earth Sciences

Introduction to Urban Water Distribution

NEMANJA TRIFUNOVI_

LONDON / LEIDEN / NEW YORK / PHILADELPHIA / SINGAPORE

© 2006 Taylor & Francis Group, London, UK

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British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

Library of Congress Cataloging in Publication Data

Trifunovi-, N

Introduction to urban water / N Trifunovi-

p.cm – (IHE Delft lecture note series)

1 Municipal water supply 2 Waterworks I Title II Series

The more we learn, the less we know as we realise how much is yet to be discovered.

3.3 Single pipe calculation 74

4.5.7 Service connections 196

Contents IX

APPENDIX 2 DESIGN EXERCISE 304

X Introduction to Urban Water Distribution

A5.5 Gravity supply 445

Contents XI

This book comprises the training material used in the three-week module

‘Water Transport and Distribution 1’, which is a part of the 18-monthMaster of Science programme in Water Supply Engineering Specialisa-tion at UNESCO-IHE Institute for Water Education in Delft, TheNetherlands Participants in the programme are professionals of variousbackgrounds and experience, mostly civil or chemical engineers, work-ing in water and sanitation sector from over 40, predominantly develop-ing, countries from all parts of the world To make a syllabus thatwould be relevant to such a heterogeneous group and ultimately equipthem with knowledge to be able to solve their practical problems wasquite a challenge

The development of the materials started in 1994 based on theexisting lecture notes made by J van der Zwan (KIWA Institute) and

M Blokland (IHE) in 1989 Their scope was widened by incorporatingthe ideas and materials of K Hoogsteen (Drenthe Water Company) and

T van den Hoven (KIWA Institute), prominent Dutch water distributionexperts and then the guest lecturers of IHE

The text was thoroughly revised in 1998 and further expanded byadding the workshop problems In 2000, the design exercise tutorial wasprepared, and finally in 2003 a set of so-called spreadsheet hydrauliclessons was developed for better understanding of the basic hydraulicconcepts, and as an aid to solving the workshop problems All theseimprovements were geared not only by developments in the subject, butalso resulted from a search for the optimal method in which the contentscould be understood within a couple of weeks The way the lecture notesgrew was derived from lively discussions that took place in the class-room The participants reacted positively to each new version of thematerials, which encouraged me to integrate them into a book for a wideraudience

During the work on the book, I came into contact with a number ofUNESCO-IHE guest lecturers who also helped me with useful materialand suggestions J Vreeburg (KIWA Institute & Delft University ofTechnology) and J van der Zwan reviewed the draft text, whilst manyinteresting discussions were carried out with several other Dutch watersupply experts, most recently with C van der Drift (Municipal Water

Company of Amsterdam) and E Arpadzi- (Water company ‘Evides’ inRotterdam) Giving lectures in Delft and abroad on various occasions,where similar programmes were also taking place, has allowed me tolearn a lot from interaction with the participants who brought to myattention many applications and practices that differ from Europeanpractice.

Last but not least, I wish to mention D Obradovi- from BelgradeUniversity, a long-serving guest lecturer at UNESCO-IHE, whose mate-rials were also used in this book Prof Obradovi- was a pioneer of waterdistribution network modelling in former Yugoslavia, an advisor ofWessex Water PLC in UK, and the author of numerous publications andbooks on this subject Sadly, he passed away just a few days before thefirst draft of the text was completed

Nemanja

Trifunovi-Preface XIII

The remains of probably the most remarkable and well-documentedancient water supply system exist in Rome, Italy Sextus Julius Frontinus,the water commissioner of ancient Rome in around the first century AD,describes in his documents nine aqueducts with a total length of over

420 km, which conveyed water for distances of up to 90 km to a tion network of lead pipes ranging in size from 20 to 600 mm Theseaqueducts were conveying nearly 1 million m3of water each day, whichdespite large losses along their routes would have allowed the 1.2 millioninhabitants of ancient Rome to enjoy as much as an estimated 500 litresper person per day (Trevor Hodge, 1992)

distribu-Nearly 2000 years later, one would expect that the situation would haveimproved, bearing in mind the developments of science and technologysince the collapse of the Roman Empire Nevertheless, there are still manyregions in the world living under water supply conditions that the ancientRomans would have considered as extremely primitive The records onwater supply coverage around the world at the turn of the twentieth cen-tury are shown in Figure 1.1 At first glance, the data presented in the dia-gram give the impression that the situation is not alarming However, thenext figure (Figure 1.2) on the development of water supply coverage inAsia and Africa alone, in the period 1990–2000, shows clear stagnation.This gives the impression that these two continents may be a few gener-ations away from reaching the standards of water supply in North Americaand Europe Expressed in numbers, there are approximately one billionpeople in the world who are still living without access to safe drinkingwater

The following are some examples of different water supply standardsworldwide:

1 According to a study done in The Netherlands in the late eighties

(Baggelaar et al., 1988), the average frequency of interruptions

affect-ing the consumers is remarkably low; the chance that no water will runafter turning on the tap is once in 14 years! Despite such a high level

of reliability, plentiful supply and affordable tariffs, the average tic water consumption in The Netherlands rarely exceeds 130 litres perperson per day (VEWIN, 2001)

domes-2 The frequency of interruptions in the water supply system of Sana’a,the capital of the Republic of Yemen, is once in every two days Theconsumers there are well aware that their taps may go dry if kept onlonger than necessary Due to the chronic shortage in supply, the waterhas to be collected by individual tanks stored on the roofs of houses.Nevertheless, the inhabitants of Sana’a can afford on average around

90 litres each day (Haidera, 1995)

3 Interruption of water supply in 111 villages in the Darcy district of theAndhra Pradesh State in India occurs several times a day House

2 Introduction to Urban Water Distribution

Rural Urban

Total

0 20 40 60 80 100

Global Africa Asia South and Central America

Oceania Europe North America

Percentage

Figure 1.1 Water supply

coverage in the world

(WHO/UNICEF/WSSCC,

2000).

Rural Urban

Total

0 20 40 60 80 100

Africa in 1990 Africa in 2000 Asia in 1990 Asia in 2000

Percentage

Figure 1.2 Growth of water

supply coverage in Africa and

Asia between 1990–2000

(WHO/UNICEF/WSSCC,

2000).

connections do not exist and the water is collected from a central tankthat supplies the entire village Nevertheless, the villagers of the Darcydistrict are able to fetch and manage their water needs of some

50 litres per person per day (Chiranjivi, 1990)

All three examples, registered in different moments, reflect three ent realities: urban in continental Europe with direct supply, urban inarid area of the Middle East with intermittent supply but more or lesscontinuous water use, and rural in Asia where the water often has to becollected from a distance Clearly, the differences in the type of supply,water availability at source and overall level of infrastructure all havesignificant implications for the quantities of water used Finally, thestory has its end somewhere in Africa, where there is little concern aboutthe frequency of water supply interruptions; the water is fetched in buck-ets and average quantities are a few litres per head per day, which can be

differ-better described as ‘a few litres on head per day’, as Figure 1.3 shows.

The relevance of a reliable water supply system is obvious The mon belief that the treatment of water is the most expensive process inthose systems is disproved by many examples In the case of TheNetherlands, the total value of assets of water supply works, assessed in

com-1988 at a level of approximately US$5 billion, shows a proportion wheremore than a half of the total cost can be attributed to water transport anddistribution facilities including service connections, and less than half isapportioned to the raw water extraction and treatment (Figure 1.4) More

Water Transport and Distribution Systems 3

Figure 1.3 Year 2000

somewhere in Africa.

recent data on annual investments in the reconstruction and expansion ofthese systems, presently at a level of approximately US$0.5 billion, areshown in Figure 1.5.

The two charts for The Netherlands are not unique and are likely to

be found in many other countries, pointing to the conclusion that port and distribution are dominant processes in any water supply system.Moreover, the data shown include capital investments, without exploita-tion costs, which are the costs that can be greatly affected by inadequatedesign, operation and maintenance of the system, resulting in excessivewater and energy losses or deterioration of water quality on its way toconsumers Regarding the first problem, there are numerous examples ofwater distribution systems in the world where nearly half of the totalproduction remains unaccounted for, and where a vast quantity of it isphysically lost from the system

trans-Dhaka is the capital of Bangladesh with a population of some

7 million, with 80% of the population being supplied by the local watercompany and the average daily consumption is approximately 117 litresper person (McIntosh, 2003) Nevertheless, less than 5% of the con-sumers receive a 24-hour supply, the rest being affected by frequentoperational problems Moreover, water losses are estimated at 40% of thetotal production A simple calculation shows that under normal condi-tions, with water losses, say at a reasonable level of 10%, the same pro-duction capacity would be sufficient to supply the entire population ofthe city with a unit quantity of approximately 140 litres per day, which isabove the average in The Netherlands

Hence, transport and distribution systems are very expensive evenwhen perfectly designed and managed Optimisation of design, operationand maintenance has always been, and will remain, the key challenge ofany water supply company Nowadays, this fact is underlined by thepopulation explosion that is expected to continue in urban areas, partic-ularly of the developing and newly industrialised countries in the comingyears According to the survey shown in Table 1.1, nearly five billionpeople will be living in urban areas of the world by the year 2030, which

4 Introduction to Urban Water Distribution

Transport & Distribution

Treatment

Extraction

Others Connections

Figure 1.4 Structure of assets

of the Dutch water supply

Figure 1.5 Annual investments

in the Dutch water supply works

(VEWIN, 2001).

Table 1.1 World population growth 1950–2030 (UN, 2001).

Region Total population (millions)/urban population (%)

1950 1975 2000 2030 North America 172/64 243/74 310/71 372/84 Europe 547/52 676/67 729/75 691/83 Oceania 13/62 21/72 30/70 41/74 South and Central America 167/41 322/61 519/75 726/83 Asia 1402/17 2406/25 3683/37 4877/53 Africa 221/15 406/25 784/38 1406/55 Global 2522/28 4074/38 6055/47 8113/60

is over 70% more than in the year 2000 and three times as many as in

1975 The most rapid growth is expected on the two most populated andpoorest continents, Asia and Africa, and in large cities with between oneand five million and those above five million inhabitants, so-calledmega-cities, as Table 1.2 shows

It is not difficult to anticipate the stress on infrastructure that thosecities are going to face, with a supply of safe drinking water being one

of the major concerns The goal of an uninterrupted supply has alreadybeen achieved in the developed world where the focus has shiftedtowards environmental issues In many less developed countries, this isstill a dream

1.2 DEFINITIONS AND OBJECTIVES

1.2.1 Transport and distribution

In general, a water supply system comprises the following processes(Figure 1.6):

1 raw water extraction and transport,

2 water treatment and storage,

3 clear water transport and distribution

Transport and distribution are technically the same processes in whichthe water is conveyed through a network of pipes, stored intermittentlyand pumped where necessary, in order to meet the demands and pres-sures in the system; the difference between the two is in their objectives,which influence the choice of system configuration

Water transport systems Water transport systems comprise main transmission lines of high and

fairly constant capacities Except for drinking water, these systems may

be constructed for the conveyance of raw or partly treated water As apart of the drinking water system, the transport lines do not directly serveconsumers They usually connect the clear water reservoir of a treatment

Water Transport and Distribution Systems 5

Table 1.2 World urban population growth 1975–2015 (UN, 2001).

Areas Population (millions)/% of total

1975 2000 2015 Urban, above 5 million inhabitants 195/5 418/7 623/9 Urban, 1 to 5 million inhabitants 327/8 704/12 1006/14 Urban, below 1 million inhabitants 1022/25 1723/28 2189/31 Rural 2530/62 3210/53 3337/46 Total 4074/100 6055/100 7154/100

plant with some central storage in the distribution area Interim storage

or booster pumping stations may be required in the case of longdistances, specific topography or branches in the system

Branched water transport systems provide water for more than onedistribution area forming a regional water supply system Probablythe most remarkable examples of such systems exist in South Korea.The largest of 16 regional systems supplies 15 million inhabitants of thecapital Seoul and its satellite cities The 358 km long system of concretepipes and tunnels in diameters ranging between 2.8 and 4.3 metreshad an average capacity of 7.6 million cubic metres per day (m3/d) in2003

However, the largest in the world is the famous ‘Great Man-madeRiver’ transport system in Libya, which is still under construction Itsfirst two phases were completed in 1994 and 2000 respectively Theapproximately 3500 km long system, which was made of concrete pipes

of 4 metres in diameter, supplies about three million m3/d of water This

is mainly used for irrigation and also partly for water supply of the cities

in the coastal area of the country After all the three remaining phases ofconstruction have been completed, the total capacity provided will beapproximately 5.7 million m3/d Figure 1.7 gives an impression ofthe size of the system by laying the territory of Libya (the grey area) overthe map of Western Europe

6 Introduction to Urban Water Distribution

Source – water extraction

Production – water treatment

Distribution

Transport raw water

Transport clear water

Figure 1.6 Water supply system processes.