Studies reports in hydrology 27

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Studies and reports in hydrology 2 7

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Recent titles in this series

20. Hydrological m a p s . Co-édition Unesco- WMO.

21 * World catalogue of very large floods/Repertoire mondial des très fortes crues.

22. Floodflow computation. Methods compiled from world experience.

23. Water quality surveys.

24. Effects of urbanization and industrialization on the hydrological regime and on water quality. Proceedings of the Amsterdam Symposium, October 1977/Effets de l'urbanisation et de l'industrialisation sur le régime hydrologique et sur la qualité de l'eau. Actes du Colloque d'Amsterdam, octobre 1977. Co-edition IAHS- Unesco/Coédition AISH-Unesco.

25. World water balance and water resources of the earth. (English edition).

26. Impact of urbanization and industrialization on water resources planning and management.

27. Socio-economic aspects of urban hydrology.

* Quadrilingual publication : English — French — Spanish — Russian.

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Socio-economic aspects of urban hydrology

Based on a report on socio-economic aspects of urban hydrology by Gunnar Lindh

Prepared at a workshop, in Lund, Sweden, under the direction of R . M . Berthelot

(unssoo

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Published in 1979 by the

United Nations Educational, Scientific and Cultural Organization Place de Fontenoy, 75700 Paris

Printed by Offset Aubin, Poitiers

T h e designations employed and the presentation of the material in this publication

do not imply the expression of any opinion whatsoever on the part of the publishers concerning the legal status of any country or territory, or of its authorities, or concerning the frontiers of any country or territory.

ISBN 92-3-101702-0

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Preface

The 'Studies and Reports in Hydrology' series, like the related collection of 'Technical Papers in Hydrology', was started in 1965 when the International Hydrological Decade was launched by the General Conference of Unesco at its thirteenth session. The aim of this undertaking was to promote hydrological science through the development of international co-operation and the training of specialists and technicians.

Population growth and industrial and agricultural development are leading to constantly increasing demands for water, hence all countries are endeavouring to improve the evaluation of their water resources and to make more rational use of them. The IHD was instrumental in promoting this general effort. When the Decade ended in 1974, IHD National Committees had been formed in 107 of Unesco's 135 Member States to carry out national activities and participate in regional and international activities within the IHD programme.

Unesco was conscious of the need to continue the efforts initiated during the International Hydrological Decade and, following the recommendations of Member States, the Organization

decided at its seventeenth session to launch a new long-term intergovernmental programme, the International Hydrological Programme (IHP), to follow the decade. The basic objectives of the IHP were defined as follows:

(a) To provide a scientific framework for the general development of hydrological activities;

(b) To improve the study of the hydrological cycle and the scientific methodology for the assessment of water resources throughout the world, thus contributing to their rational use;

(c) To evaluate the influence of man's activities on the water cycle, considered in relation to environmental conditions as a whole;

(d) To promote the exchange of information o n hydrological research and on new developments in hydrology;

(e) To promote education and training in hydrology;

(f) To assist Member States in the organization and development of their national hydrological activities.

The International Hydrological Programme became operational on 1 January 1976 and is to be executed through successive phases of six years' duration. IHP activities are co-ordinated at the international level by an intergovernmental council composed of thirty Member States.

The members are periodically elected by the General Conference and their representatives are chosen by national committees.

The purpose of the continuing series 'Studies and Reports in Hydrology' is to present data collected and the main results of hydrological studies undertaken within the framework of the decade and the new International Hydrological Programme, as well as to provide information on the hydrological research techniques used. The proceedings of symposia will also b e included. It is hoped that these volumes will furnish material of both practical and theoretical interest to hydrologists and governments and meet the needs of technicians and scientists concerned with water problems in all countries.

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1. Introduction—purpose and scope

1.1 BACKGROUND

In 1973 an international Workshop on the Hydrological Effects of Urbanization was convened in Warsaw by Unesco. During this Workshop the preliminary report of the Unesco International Hydrological Decade (IHD) Subgroup on the Effects of Urbanization on the Hydrological

Environment formed the basis of discussion. As a result a publication entitled 'Hydrological effects of urbanization' was printed in 1974 as number 18 in the series of Studies and reports

•in hydrology. The work of the Subgroup was initiated in order to assist the Working group on the Influence of Man on the Hydrological Cycle. The importance of hydrological effects of urbanization was thereby recognized early in the work of the IHD.

The members of the Subgroup, which had worldwide representation, felt strongly the need for a better understanding of the urban problem and its inter-relationship with urban hydrology. From the foreword of the report emanating from the Warsaw Workshop, it appears that one of the major conclusions was that the field of urban hydrology requires more modern research investment. There has been relatively little study to date of the effect of urban man upon natural hydrological conditions, in spite of the significant economic and environmental importance of urban settlements in nearly every nation. It was expected that the report would inspire more extensive research and development in individual countries and would lead to the formulation of improved plans for international cooperation on research subjects of widespread general interest. (McPherson, 1974a).

The results of the work carried out by the Subgroup was reported to the International Conference held in Paris in 1974 (Unesco, 1974a), which discussed the results of the Inter- national Hydrological Decade and future programmes in hydrology. At the first session of the Intergovernmental Council of the International Hydrological Programme (IHP) held in Paris in 1975 it was proposed to prepare a state of the art report or. the known economical, social and environmental relationships of urban hydrology. The intention was that in this report, the growth of urban problems of crowding, water supply, waste disposal and general environmental quality would be emphasized.

At the request of the Intergovernmental Council of the IHP, Professor Gunnar Lindh, University of Lund, Sweden, prepared a draft report which was reviewed during the Workshop on Socio-Economic Aspects of Urban Hydrology held in November 1976 in Lund, Sweden. The draft formed the basis of this publication. A list of participants in the Workshop is given in Appendix 3. They included city planners, economists, sociologists, ecologists, biologists, historians, civil engineers and hydrologists.

The contents and conclusions of this report were used as an input to the Workshop on the Impact of Urbanization on Regional and National Watermanagement and Planning, held in the Netherlands in October, 1977. At this Workshop, technical and planning aspects, as well as the use of planning models were discussed.

The recommendations from both the Lund and Netherlands workshops will be used for the planning of urban water projects and programmes in the next phases of the International Hydrological Programme.

1.2 IMPORTANCE OF URBAN HYDROLOGY

1.2.1 Comments on the term 'urban hydrology'

The title of this report contains the term 'urban hydrology'. In order to understand what is meant by this term, let us recall that there is an internationally accepted definition of hydrology which reads:

'Hydrology is the science that deals with the waters of the Earth, their occurrence, circulation and distribution, their chemical and physical

properties, and their reaction with the environment, including their relation to living beings.'

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Importance of urban hydrology

Logically urban hydrology should be understood as an application of hydrology (as defined above) to phenomena restricted to the urban region. Hydrology provides the

scientific basis for explaining and understanding the whole range of water-related activities.

However, it was pointed out by many delegates at the First session of the Intergovernmental Council of the Unesco International Hydrological Programme (Unesco, 1975a) that hydrology and water resources formed an inseparable unit and in many countries are merged. The 18th session of the General Conference of Unesco authorized the Director-General 'to stimulate the development of educational activities relating to the water sciences....' (Unesco, 1974b).

Few attempts have been made to define urban hydrology in the literature. However, it is a distinct branch of the broad field of hydrology, because the complex interactions of

human activity with air, water and land must be collectively taken into account in concentrated settlements. In other words, the impact of man on the water cycle is greatest per unit area in urban places (McPherson, 1974a).

A possible definition of urban hydrology is:-

"The interdisciplinary science of water and its interrelationship with urban man.'

The broad, intimate man-water concept of urban hydrology has prompted a new look at traditional urban thinking and approaches (Jones, 1971c).

We propose that by urban hydrology shall be understood those processes occurring in the urban hydrological environment. This environment must include the existing metropolitan area, the area for expected future expansion, and the surrounding area which influences the urban water cycle. Included in the concept of urban hydrology are factors such as

precipitation, surface runoff, groundwater and water supply affecting inflow to the urban hydrological environment. We have also to take into account évapotranspiration, streamflow,

storm drainage, waste water and groundwater as outflow from the urban hydrological environment (McPherson, 1969).

1.2.2 Current problems of urban hydrology

As the title of this report - Socio-economic aspects of urban hydrology - implies, it deals with the relationships between social and economic factors and urban hydrology. Problems encountered in this context originating from the need to provide water supplies for urban areas, affect many people, involve so much water and entail so large an expenditure of money that it is necessary to consider them in detail. The costs of providing metropolitan water services are escalating rapidly. The replacement cost of existing urban systems providing necessary water services in the USA, for example, is in the vicinity of $175 billion and it is estimated that some $15 billion per year will be spent in the next few years for new construction. Combined capital and other current expenditures for water supply, waste collection and disposal in 38 of the USA Standard Metropolitan Statistical Areas were estimated in 1969 at $30.50 per capita and represented 20 per cent of total capital outlays and 4 per cent of other current expenditures. Both the amounts and percentages can be expected to rise dramatically in the future in order to achieve higher standards of water pollution control. (US National Water Commission, 1973).

In order to analyse the role of urban hydrology more closely, it could be broadly stated that water is part of the renewable natural-resource base. Beyond its importance for the support of life, water is essential for the further expansion of urban areas. Its biological function has a parallel in the social and economic metabolism of society.

With regard to urbanization and the role of water, it may be noted that a characteristic feature of urbanization is that it drastically changes the natural conditions where water distribution was governed by climate and the physical character of the land surface. Water is now used both to supply man's need and to carry away his wastes. In that sense, water in the urban environment fulfils the functions of both arteries and veins of urban life (Schneider, Richert and Spieker, 1973).

In analysing the role of water in urban society, water may be regarded not only as

1 American billion: 1,000,000,000

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Marty culture, physical environment - aspects of well-being

a resource serving the social good but also as a nuisance. The role played by water as a resource is almost self-evident but the role as a nuisance may need some consideration especially since social and economic aspects of urban hydrology are so closely related. It should be underlined that many uses of water may reduce quantity and impair quality.

Consequently, the value of water as a natural resource is reduced to the detriment of individuals or the public well-being.

The right to use water is recognized and protected as a property right. Thus if water quality is affected and such is proved, it remains to weigh the merits of the respective rights of all parties involved (Thomas and Schneider, 1970). The right to use water in an urban society is not directly delegated to individuals but the community because individually- held land is generally too small to provide adequate supply, storage, or disposal of water for its occupants. Similarly, each individual may be concerned about water as a nuisance.

Apart from creating minor disturbances of well-ordered life such as puddles, mud in unpaved areas, eroding ground, carrying flood-debris and filth, water itself is a repository of urban wastes. Water pollution is only one aspect of a much more complex problem of handling

urban wastes. The severity of this pollution problem depends upon the degree of waste treatment and the amount of waste in relation to the amount of water available. This in turn reveals one of the most intricate problems of urban water sciences and engineering of today, namely the lack of an overall approach to the treatment of urban wastes.

Since urban hydrology as a science is responsible for the proper analysis of such problems, it may be emphasized that there exists today no correspondence between the degree of treatment, the treatment plant and the treatment desirable for the protection of the receiving body. This is not the only instance where an ambitious engineering achievement has overlooked the integrated approach. Another important example may be found in the

current intensive study of urban-water runoff. The large amounts of money which are allocated for the conveyance of storm water might be better used if the complexity of the problem were better understood.

It is important to be aware of the fact that many urban activities are closely related to the development and use of the land. Such activities may affect the natural water-flow system and all other systems may in time be affected by it. In this sense, one must guard against the violation of the individual's and society's rights, either through land development that adversely affects water processes or through water mismanagement which will affect land resources.

To the problems just mentioned, where urban hydrology has to play an important role, may be added urban runoff. The problem of dealing with these sometimes tremendous amounts of water in addition to heavy pollution loads is exacerbated where rainfall flushes contaminants from urban streets. To these urban water problems can be added the problem of disposal of solid wastes in dumps and sanitary landfills. Such disposals often cause severe pollution of groundwater as well as of surface water due to leaching. Both biological and chemical contamination are liable to occur.

Another water-related problem is associated with the construction of housing and highways which may expose bare soil and thereby accelerate erosion. Such erosion may choke streams with sediment and fill reservoirs. This, in turn, may severely limit the use of water

bodies for recreation and aesthetic enjoyment and reduce their capacity to accommodate floods.

Another phenomenon which is amplified in urban areas is the flooding process. Roofs, paved surfaces and installation of storm sewers increase the flooding hazards by concentrating the storm runoff. Besides these physical effects on the water resources, urbanization may also alter the recreational and aesthetic values of water bodies. Degradation of the urban environment may destroy aesthetic appeal and decrease recreational potential of areas in or adjacent to the urban region (Schneider, Rickert and Spieker, 1973).

The above illustrates urban water problems to the solution of which hydrological methods may be effectively applied. It would, however, be a mistake to believe that water-related activities in an urban system are limited to the urban area itself. As water supply becomes increasingly inadequate in relation to domestic and industrial demands, it may have to be augmented from other areas. The necessity to import is not restricted to water, imports of fuel, food and other materials are essential for sustaining urban life. This means that hydrological effects caused by the urban population are not limited to the urban area but affect a wider area. This is particularly so in areas of water shortage. In general, water can no longer be taken for granted as a readily available urban commodity.

Man's activities have also brought to light the interrelationship between water and other natural resources. Very often, however, man's measures to solve problems of water

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Man, culture, physical environment - aspects of well-being

supply and waste removal have been characterized by concentrating on discrete functions and single approaches. The result of such practices has led to rapid eutrophication of lakes, pollution of rivers, and degradation of recreational and aesthetic benefits of water

resources. Urban planning and management must therefore be based on sound consideration of interaction and interdependency of all relevant natural resources, among them water.

We assert that urban hydrology has the important function to provide for the rational and efficient use of water in the urban society. It is implicit that this task is subject to the socio-economic constraint of the urban society.

The foreword of the report of the IHP Subgroup on the effects of urbanization on the hydrological environment ends with the statement that 'so many similarities were found in problems and effects that it is concluded that the findings of this report are more univers- ally representative than the small sample of nations involved would suggest.' However, it is important to realize that there may be considerable differences among urban hydrological problems when we look at the different regions in the world. Considering, for instance, man's intervention in the environment, we may expect that the effects thereof will depend on the locally prevalent specific situation. Thus, not only the characteristic features of the urban area but also climatological, geographical, social, economic and political factors may cause a situation which has its specific importance. This means that it may be difficult to find generally applicable solutions to urban hydrological problems, especially as there could prove to be notable differences between urban areas in developed and in developing areas.

It has been demonstrated in a number of countries that urbanization increases the volume of direct runoff locally and that systems of storm drainage conduits create higher direct runoff peaks with a shorter rise time than in pre-urban conditions. A cause of existing generalizations is that, world-wide, the field of urban hydrology is almost devoid of modern research investment and that there has been relatively little study to date of the effect of human settlements upon natural hydrological conditions (McPherson, 1973).

The hydrology of urban areas is exceedingly complex and is not yet completely understood.

One reason for this may be that in urban hydrology the peculiar nature of the gauging problem, associated with runoff and other processes, have been seriously neglected. Inade- quate data are available for evaluating the effect of urbanization on many hydrological phenomena. In itself, the urban drainage area is highly variable in such characteristics as slope, size, shape, roughness and degree of imperviousness, and because of this many urban hydrological studies have been limited to small, controlled plots with major emphasis on the rainfall-runoff relationship. Moreover, in urban areas crude estimations are often substituted for reliable data. In a peak-flow-frequency analysis, using historical records, the assumption is often made that all events are random. Moreover, the assumptions may be made that they have occurred under similar water-basin conditions. This is not always true because of changes in land use and improvement in drainage facilities accompanying urban development over a period of time (Robey, 1970).

1.3 MAN, CULTURE, PHYSICAL ENVIRONMENT - ASPECTS OF WELL-BEING

The title of the present report indicates that what has to be analysed are the interactions between socio-economic variables and hydrology within the urban domain. In order to understand such a problem, we have to combine experiences from a variety of disciplines, especially sociology, economics and hydrology, each with its own constraints and possible reactions from the physical environment, directly, or through feed-back loops. The attempted understanding must fulfil an expressed desire for what may be called the harmonious relationship among the three parts that comprise the term total environment, ie man, culture and physical

environment. This terminology is taken from Vlachos and Flack (1974) who list a series of problems arising from the expansion of the urban water-resource systems - misuse, abuse, or neglect of the urban water and related land resources :

1. The alteration and even destruction of the natural and hydrological balances in the urban area.

2. The modification of natural runoff patterns by urban development.

3. Environmental degradation, especially through a lack of willingness to design and conduct activity in a manner that may preserve and

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Socio-economic aspects of urban hydrology versus water management and planning

enhance elements of the natural environment.

4. The basic lack of knowledge and understanding of the inter- relationship between man, his culture and the surrounding physical environment.

5. The difficulty in identifying beneficiaries in the densely- settled urban areas and the concomitant difficulty in allocating accurately costs and benefits.

6. Inadequate financial capacity.

7. Conflicts of interest and conflicting attitudes of groups with special interests and people in general vis-a-vis public officials.

8. The unwillingness of land owners to contribute to a solution of the problem which does not directly affect them.

9. Lack of comprehensive integrated planning as well as administrative fragmentation and absence of uniform quality of services.

In an attempt to analyse the dimension of the inter-relationship between man, culture and environment, this report attempts to review research around such concepts as quality of life, well-being, etc. Depending on the type of society and political, geographical and other

factors the summarization of, for instance, social well-being and quality of life (SWB/QOL) will be characterized by a set of objective and subjective indicators. Such lists abound

in the literature, but they are subject to theoretical debates, definitional discrepancies and often lack empirical data for specific reference. These indicators and their arrangement in order of importance will, in turn, be influenced by the types of society, etc. Consequently the order will reveal the importance played by water for individuals and societies compared with other factors on the list. Whether or not this is a way to take care of the social aspects of water use in the urban life is still open to question. However, it seems to be a logical way to approach the problem. The success of this approach may depend on the future development of sociological studies in characterizing man's conception of his life as a member of an urban society. The concept of well-being (SWB/QOL) will also be important as seen from the point of view that we need some mechanism by which we may register the response of alternative actions taken. These al terna ti-ves are being presented as economic-technical proposals worked out with proper consideration of possible environmental interactions.

Using the broad criteria SWB/QOL, we may be able to develop criteria for considering, in a systematic fashion, human factors in water resource projects.

In order to overcome the obviously serious difficulties likely to emerge if we use the notion of SWB/QOL, more direct and simpler methods can be used as substitutes. This implies that as a first approach basic life conditions (such as health, transport, and especially economic factors) can be presented as a first step in outlining elementary objective conditions of well-being. More refined indicators and additional social considerations can then be used as constraints that may modify the hydrological-economic relationships. Such an approach will evidently restrict the degrees of freedom of the complex system being considered, and thereby delimit the possibilities of generalizing the results obtained. Due to the lack of complete knowledge of the impact of social factors on the urban water system, the method proposed may be justified. In addition, basic survival life conditions may be the necessary analytical thrust for developing countries. It is at much later stages of development that more complex indicators of well-being become more meaningful or necessary.

1.4 SOCIO-ECONOMIC ASPECTS OF URBAN HYDROLOGY VERSUS WATER MANAGEMENT AND PLANNING This state of the art report on socio-economic aspects of urban hydrology can be considered as basic introductory material for the Netherlands' Workshop, in 1977, on the impact of urbanization on regional and national water planning and management. In this sense, the report cannot be made without due regard to this activity. It should be understood that

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Socio-economie aspeata of urban hydrology versus water management and planning

knowledge of social and economic factors is a prerequisite for successful planning and management. Moreover, we have to explain the constraints of socio-economic factors in technological solutions. Multi-purpose planning - taking into consideration socio-economic aspects of urban hydrology - must establish a wider range of alternatives, since technological solutions also entail changes in life style, level of consumption and similar broader cultural alterations.

The previous considerations have been stressed by many as a vital strategy in urban-water planning. It is a strategy whose main characteristics involve multi-objective, multi-purpose planning. The process itself, through public involvement and successive interactions, is an evolutionary one in both attempted goals and public preferences.

A multi-purpose, multi-objective approach implies taking into account a full range of alternatives, including scientific research as a tool for devising new technologies affecting both demand and supply. For this reason, it would utilize a mixture of public and private administrative instruments, encouraging as much decentralization of choice among individuals and local agencies, as consistent with broad guidelines supported by public consensus.

Standards for water quality, hazard reduction, and social valuation would not be rigid, but decisions would be based on criteria for keeping the range of choice as wide as practicable and working toward short-time horizons within frameworks describing longer-term human needs and physical limits. There would be intensive investigation of resources and the theoretical possibilities and social consequences of altering them. In many cases, the dispersal of population along vast metropolitan areas requires that planning should be based on a larger metropolitan organization (White, 1971).

Thus, aspects of multi-purpose planning are intertwined with social, economic, public and institutional factors, with emphasis on the interrelation between planning and environmental effects. In turn, multi-purpose planning with regard to the urban-water situation leads to modelling of systems. Planning models require a certain amount of intensive hydrological modelling by which parameters and indicators may be established. Thereby one provides a means of understanding hydrological processes so that simplified expedients are not inadvertently misused (McPherson and Schneider, 1974).

The term water management, widely used only in the last decade, has not yet a specific meaning. Although rational control of water is its objective, there is no common understanding of policies and institutions required for achieving rational control. Management functions can be roughly divided into a formulative, or strategic, level dealing with goals and policies, and on administrative, or tactical, level concerned with their implementation

(McPherson, 1970).

Leaving the precise and strict meaning of water management aside for the moment, it is recognized that a close inter-relationship exists between water management and socio-economic development. As a consequence of the latter, water-demands grow at accelerating rates and properties, increasing in value, must be protected from the damages of water. At the same time, and conversely, advanced water-management is one of the prerequisites for socio-economic evaluation, since the scarcity, abundance, or poor quality of water present potential limits to such an evaluation. (Vincze, 1974).

The determination of urban-water-management requirements, resulting from social trans- formation, economic development, international cooperation and rising standards of living, further the exploration of ways of carrying out the task of long-term water-management planning.

As to medium-term water-management plans, they identify the more important water-development objectives envisaged in the long-term plan for a longer period, say five years. For the different urban-water management organizations, the uniform system and quantities of the technical-economic means needed must then be specified. (Bekesi, 1974).

Given all the above, it becomes apparent that urban hydrologists, urban planners and those in other related disciplines have to cooperate in the study of a series of urban

problems. Obviously, there also exist apparent obstacles to such a collaboration. We may use as an example urban hydrologists and urban planners. The former are trained in physical

sciences, or engineering, whereas urban planners' training is in social sciences or landscape architecture. Per se this should be a good thing since we would then have all aspects of urbanization covered by a broad spectrum of joint experiences. However, in reality, there are substantial difficulties in communication as well as approaches to problems and inter- pretation between these two groups. The solution to such dilemmas must be found in an understanding of each other's role in the common work. This means that the planner must be aware of the hydrological factors in his planning and the urban hydrologist must acquire knowledge

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Socio-economic aspects of urban hydrology versus water management and planning

of the rigorous analytic methods nowadays used by urban planners (Schneider, Richert and Spieker, 1973). Together they have to develop an alternative/resource-impact relationship as an essential ingredient for effective decision making. It is necessary that a close team-work has to be established through interdisciplinary dialogue, integrated framework and interrelated field activies. Through continuous exchange of information common checking of the validity of presented alternatives and mutual sensitivity to the integrated nature of urban analysis, a unified approach can become possible. Such an evaluation of an interdisciplinary effort may be graphically illustrated by Figure 1.1. This figure attempts to delineate a common effort starting with the identification of problems and definition of objectives. The ultimate goal is an improved urban development which can be approached through alternative paths as shown in the diagram. While the upper part in the diagram shows how the urban planner acts, the lower part shows the inputs of the water-resources scientist.

Socio-economic aspects as well as technical, institutional, legal and political items are included in the common efforts (Schneider, Richert and Spieker, 1973).

The previous remarks exemplify the central responsibility of the urban hydrologist in judging the merits of alternatives and the need for being informed about urban planning.

However, experience has shown that in many instances, communication becomes a one-way process rather than a meaningful dialogue. There is no doubt that there are technical constraints on effective planning (such as inadequate quantitative hydrological data as

well as inadequate data on environmental and socio-economic matters). More important, however, is the essential need for an effective and legal framework in which planning can take place

(Banks and Williams, 1973).

The importance of teamwork must be repeatedly stressed. One reason, not mentioned so far, is that for the next few decades, we will have to look at urban problems no longer as containing problem areas composed of discrete and essentially closed systems of buildings, utility lines and roads. Instead, we must adopt a broader social system approach. That means that social organization, human needs, and interrelated activities are replacing individual components as the foci of planning inquiry and strategy. This emphasizes the need for an integrated approach beyond specialized disciplines, with particular sensitivity to the social-historical character of technical development. Clearly implied is a problem-oriented approach for investigative and research as opposed to a purely disciplinary approach.

New specialists can claim no loyalties to any one particular discipline and, thus, there is, and will continue to be, an erosion of disciplinary boundaries. This is also due to the accumulation and refinement of integrative theory and the acceptance of once alien

concepts that had been the exclusive property of other disciplines. New computer tools and techniques will play a special role in this context, as well as the legal requirements in a number of countries promoting interdisciplinary integration.

For several years now, civil engineers have found themselves increasingly involved with economists and social scientists and have also become members of problem-oriented teams resulting in the erosion of the dualism that has, in the past, maintained boundaries between different professional groups. However, there still exist certain polar distinctions such as analysis versus design, systems and operations research versus more traditional isolated analysis and design, technical isolation versus total involvement etc. The civil engineer must look particularly to new analytical tools, such as a systems approach to changes in human needs as defined by the environmental ecologists. In lieu of further elaboration of

this topic, interdisciplinary links - both present and suggested for the future - are diagrammatically shown in Figure 1.2. At present (Figure 1.2a), specialist disciplines tend to integrate their work side-by-side and it is difficult to reach beyond neighbouring fields.

The human perspective tends to be subordinated. In the future (Figure 1.2b), the specialist disciplines may work with a common integrating centre I. Inside I are the human sciences and bio-ecology as well as the specialists on integration.

Finally, the new requirements for environmental impact studies, as well as proposed

changes to broaden the basis of planning to include land use, may also contribute significantly to a better understanding of disciplinary inputs in a common approach. This may perhaps

aid an intellectual synthesis of approach, based upon established working relationships.

While there has been much talk of interdisciplinary approaches, too little reality describes the present situation. (Whipple, 1971).

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Concluding remarks

1.5 CONCLUDING REMARKS

Like energy, water has been considered by some people as an inexhaustible resource, available at every place at the right time. Of course a shortage of water in itself reveals a problem but there are other situations which conceal the real problem. It is a well-established fact

that a number of urban areas are extremely vulnerable to variations in their water supply, for example, cities located in the upper catchment of river basins - Hyderabad in India, Denver in the USA, Addis Ababa in Ethiopia, Bogota in Colombia, and Caracas in Venezuela - to name a few. A characteristic of these cities is that in dry years they use the total available water by drawing from the watershed, reservoirs and underlying groundwater reservoirs. This may result in an irreversible process of lowering the water table and causing land subsidence.

Where cities are located along the ocean shores, depletion of groundwater may result in saline intrusion into the aquifer.

A solution of the water problem of an urban area may be to re-use the water several times. This creates social and economic problems. A variant to this is to use water of different qualities for different demands. This again stresses the social and economic, as well as environmental, aspects of water use. Moreover, we may not be unfamiliar with the idea of the use of brackish water for certain demands, or of the use of desalinated water.

This is of course a situation favourable to urban areas near the coast. If fresh water becomes expensive enough, these areas are favourably situated to meet a minor part of their needs with desalinated water which can be produced as a by-product of power plants. This is likely to happen only when the cost of adding extra water supply capacity equals the maximum experienced by a million-size city in the world today. (Meier, 1974).

Many socio-economic problems related to urban hydrology have their origin in the conflicting situation caused by a competing demand for water. To see how such conflicting situations may arise, a starting point may be to define the geographical region that encompasses the water resources used, for instance, by a city. Expansion of the city, or migration into it, may cause an enlargement of the water-resources region. When the region expands in this way, it may interfere with regions which supply agriculture, or other urban areas. Migration should not be regarded as the only reason for such conflicting situations.

They are liable to occur in areas of water shortage where a combination of extended

activities in industry, agriculture and migration may interact unfavourably. In many areas with a shortgage, water must be transferred from remote districts. This fact does not, however, ensure that no conflicts will arise, as difficulties may arise from competition.

Considering socio-economic aspects of urban hydrology, a possible solution may be to use an increasing amount of water successively for an increasing number of activities within the urban area. The lower limit of the water requirement is the amount of water which is necessary to sustain life. The upper limit may be the amount of water which, if increased would not contribute to further development of social activities. It is assumed that this water would be of suitable quality for the various needs. Social activities would include development of commercial, industrial and other activities, as well as development of water-based facilities, including recreation, for the urban population. This analysis could be performed assuming a constant population, on the basis of an optimal supply of water of a given quality, and then the effects of an increase could be studied. Such considerations may lead to the notion of a city-balanced water supply showing its relationship to a well- balanced environment. The approaches proposed are straightforward. In order to be used in a meaningful way, a series of important constraints must be taken into account. For

instance, the fact that water is not always available. Raising the level of consumption from one or more users may result in severe stresses on the available water resources. Competing use of the resources may aggravate the situation.

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2. Urban population trends

2.1 INTRODUCTION

This chapter draws attention to expansion and concentration of population. Data on these are regarded as necessary base material for a study of social and economic, as well as political, aspects of urban hydrology to be considered later in this report.

Data about population trends in different parts of the world may be regarded as useful in order to examine the relationship between social and economical factors and urban-water

characteristics in the planning for development. More generally, as stated by the United Nations Economic and Social Council (UN, 1973): "The future size, structures and distribution of population are essential for any plan that involves food, housing, employment, education, health or other public services. There is also an area of increasing awareness: of man's unprecedented growth, of the interaction between this growth and the environment, and of the possible implications for the future. Investigations into these complex relationships have aided the demand for population projections'.

It could be added that this is related to urban water management and planning and in turn to urban hydrology as well as to the quality of life. This latter concept must be the guiding one in formulation of the conditions for water demands.

From the figures given in the above mentioned ECOSOC report, it is possible to assemble the data in Table 2.1.

Table 2.1. Urban and rural populations, 1965-2000

Urban population (millions)1

1965 1970 1980 1990 2000 1158 1352 1854 2517 3329 651 717 864 1021 1174 507 635 990 1496 2155

Rural population (millions) 1965 19 70 1980 1990 2000 2131 2283 2614 2939 3186 386 374 347 316 280 1745 1910 2267 2623 2906

Percentage of urban population 1965 1970 1980 1990 2000 World total 35.2 37.2 41.5 46.1 51.1 More developed regions 62.8 65.7 71.4 76.4 80.2 Less developed regions 22.5 25.0 30.4 36.3 42.6 World total

More developed regions Less developed regions

World total

More developed regions Less developed regions

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Introduction

It appears from this table that, in 1970, 37 per cent of the entire world's population were urban; in the year 2000 the urban population is expected to reach 51 per cent of the total. Moreover it is predicted that the combined urban population of the world may increase almost two and a half-fold in the coming thirty years. It is important to note that the urban population growth differs greatly in different parts of the world. If we look at the predicted situation in developed countries we find that the urban population may grow from

717 million in 1970 to 1174 million in the year 2000. This corresponds to an increase of 457 million or 54 per cent. In contrast, the urban population in developing areas may

increase from 635 million in 1970 to 2155 million in the year 2000. If we look at the figures for rural population during the same period there is a 26 per cent decrease in developed countries and a 52 per cent increase in developing countries. The table shows that the percentage of total population in urban localities may rise from 66 to 81 per cent in the more developed regions whereas there may be an increase from 2 5 to 43 per cent in the less developed countries.

If we look closer at the predicted development of some areas of the world we note that the ratio between urban population in the year 2O00 and the year 1970 will amount to the approximate values given in Table 2.2.

Table 2.2. Ratio of urban population in the year 20O0 to that in 1970

Europe 1.5 East Asia 2.7 North America 1.7 Latin America 3.1 USSR 1.8 South Asia 3.3 Oceanic 1.9 Africa 4.2

In contrast we observe that Europe, USSR and North America may show a decrease in rural population from 1970 to 2000. In Eastern Asia an increase by 6 per cent is predicted and for Latin America an increase of 26 per cent. In Southern Asia this is equivalent to an increase of 76 per cent and in Africa 86 per cent. We may conclude that the rural population is likely to grow faster in Southern Asia and Africa than the urban population in North America and Europe. The figures are based on what is called the medium variant of population growth in the world. There are also two other variants presented by the ECOSOC analysis, namely a low and a high. What causes the differences between these variants is the point of time when the population expansion is expected to change to zero growth. According to the notion of a medium variant this is supposed to occur by the year 2125 when the total world population is estimated to reach approximately 12.3 billions . The ECOSOC calculations have, however, assumed different points of time for a state of zero growth for developed and less developed countries. For the more developed countries the medium variant assumes that the state of zero growth will be reached by the year 2095 with a total population of 1.9 billion1. For less developed countries it is assumed that there will be a further growth until the year 2130, from which time we may expect a zero growth. At that time the total population in less developed countries may amount to 10.5 billion¹. There is at present a gap between the population of developed and less developed regions and we may count on a widening gap in the future. In 1970 the total population of the world was about 3.6 billion of which approximately 75 per cent belonged to the less developed countries. Still referring to the medium variant it is forecast that this percentage will amount to 76 per cent by the year 2000, to 84 per cent by the year 2050 and to 85 per cent by the year 2100. There are other studies of the growth of population and resources which have been under international debate for years.

An interesting model was set up by J^rgensen, in 1975, for the growth of Gross National Product (GNP) and the population. The model shows that there is a relationship between GNP and the population and moreover that GNP is following a logistic growth. The model also shows where the problems are to be found. The author claims that the industrialized countries

1 American billion 1000,000,000

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Urban growth, migration, density of population, standard of living and demand for water for different purposes

carry their development too far and new countries aim at more industrialization. The result is that the production of countries with a GNP higher than $2000 per inhabitant/year would increase by eight times as much from 1970 to 2030. The developing countries are likely to continue to increase their population beyond that date as it will take longer to obtain a high enough GNP/inhabitant year to enable the birthrate to be reduced.

The way in which development of urban areas progresses is of utmost importance for the following discussion, because different kinds of societies may show different social and economical characteristics. It is a well-known fact that socio-economic development is

closely connected with the territorial concentration of productive activity and the population, ie with the agglomeration. We also know socio-economic characteristics are closely interrelated to urban hydrology and urban-water resource development. Thus, there is an apparent connection between urban regional expansion and urban hydrology. We may ask if urbanization will show a tendency to concentrate into a relatively few large urban centres which should then be a continuation of an ongoing process. Or may we expect that the migration to urban areas will be resolved into a distribution among numerous, geographically more widely distributed, urban areas of lower orders and magnitudes?

The ECOSOC report gives some answer to this last question: 'Cities with one million or more inhabitants numbered 162 in 1970 of which 83 in more developed and 79 in less developed regions. By the year 1985, there may be a total of 273 such cities, 126 in more developed and 147 in less developed regions. The population contained in this increasing number of cities may nearly double in fifteen years, from 416 million in 1970 to 805 million in 2000. The million-cities contained 31 per cent of the urban population in the year 2O00; in this respect the urban population will be more or less concentrated in large centres in the less developed, as compared with the more developed regions. By 1985 the million-cities may comprise 27 per cent of the total population in more developed regions, and 13 per cent of the total (rural and urban) populations in the less developed regions'.

2.2 URBAN GROWTH, MIGRATION, DENSITY OF POPULATION, STANDARD OF LIVING AND DEMAND FOR WATER FOR DIFFERENT PURPOSES

In order to sample information from different cities and countries a questionnaire was sent out asking for comments on:

1. Urban growth, migration and density of population (statistical data) 2. Demand for water for different uses (residential, industrial, cooling

water, etc)

3. Waste-water disposal

4. Ways of fulfilling water demands.

The enquiry was sent by Unesco to IHP National Committees in:

Australia Netherlands Austria New Zealand

Federal Republic of Germany South America

Hungary Switzerland India Turkey Italy USA Mexico

The returns were not complete nor were they in a comparable form that would have enabled the Workshop to analyse them and draw conclusions.

During the Workshop, a subgroup drew up a form (Appendix 1) for the data presented in response to the enquiry. The Workshop suggested that this form might serve as a guide for organizing and unifying similar data from other sources in the future in order to promote exchange of information between nations and research in the field of urban hydrology. The form has been used in Appendix 1 to summarize returns for Sekondi in Ghana and Hannover in the Federal Republic of Germany.

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3. Urban systems

3.1 CONCEPTS

In order to deal with water technology, water policy and management we need a terminology which, among other things, is able to relate the arguments clearly to geographical space.

There are two fundamentally different ways of approaching this matter.

The first, is to divide the land area into compact, bounded areal units that cover the whole area and do not overlap. Water basins, or government territories, are examples of such units. As a rule both decision-making competence and statistical information are attached to such units. The second, is to adopt a systems terminology and group functionally-linked elements into systems and subsystems. The elements of such systems are most frequently scattered with respect to location and extension. The intertwining of elements in space makes it impossible to draw clearcut boundaries around systems. They cannot, therefore, be easily made to coincide in a neat way with compact, bounded areal units.

As is well known any system can be viewed as part of a hierarchy of systems, with other systems placed above as well as below. In the case of urbanization it is now increasingly recognized that for purposes of regional economic and social development policies, as well as infrastructure policies (eg transportation), all urban settlements of a nation should be looked upon as forming an interacting system. This level is called 'the national settlement system' or sometimes 'the national urban system'. On the level below, we may recognize the individual urban nucleus with all its linked elements in the closer or more distant surround- ings as an 'individual urban system' or shorter an 'urban system'. This in turn is then made up of subsystems of various nature. In this report the term 'urban system' will be used for the individual subsystem in the national settlement system.

From what has been said above it is clear that we have to face a rather difficult conceptual contradiction. For empirical description, and in discussions of planning and implementation, we will have to rely mainly on the concept of bounded areal units, eg the administrative territories of cities. But, at least from a human and technological point of view, it is increasingly true that the world cannot be divided into neat, territorial compart- ments. Interaction between distant points in space has made the systems terminology preferable as a tool for real-world description and analysis. Systems concepts will therefore dominate in the present report. But it must be kept in mind that it is becoming a major problem, both in theory and in practice, to find acceptable links between the two world-views which these two predominant concepts represent.

It is also important to consider here the concept of urbanisation. Urbanisation is the process of concentration of large numbers of people in a relatively small geographical space enabling and causing a high degree of division of labour, a great variety of activities, as well as intensive and complex interactions. This process created, until recently, compact built-up areas which are virtually man-made environments clearly distinct from the rural areas.

Due to improvements in transportation and tele-communication, the urban settlements could grow further, or could be established anew in a much less concentrated way to such an extent perhaps that groups of smaller and larger settlements, with higher or lower densities, interspersed by open spaces, could come into existence, but without a breakdown of the functional relations which characterise the spatial pattern as a system. The larger urban systems are called urban regions because they are no longer a city in the classical (morphological) sense, but, never- theless, they functionally form a socio-spatial unit. Although urban regions are in many countries still growing in area, there are indications that, ultimately, this will lead to a breakdown of the system, because time and cost of transportation remain limiting factors. In several countries, planning policies aim at reconcentration of urban regions in order to regain the qualities which initiated the process of urbanisation in the past.

The gradual transition from urban to rural areas, and further to an adjacent urban area, may cause a number of hydrological as well as socio-economic problems in what is usually called a watershed in transition. Among others, Roberts (1972) has pointed out the complexity of hydrological and socio-economic problems that are to be encountered in watersheds in the rural-urban fringe.

Similarly, the creation of the megalopolis in the future may cause a series of cultural,

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The urban system

social and environmental problems. De Meló Carvalho (1969) discusses these and remarks:

"There is a great need for integration of town and country in order to avoid the artificiality of meglopolis and to bring man as close as possible to his original natural environment1. 3.2 THE URBAN SYSTEM

An urban system may be defined through identification of those entities, or subsystems, which constitute the urban system in question. The nomenclature we use depends upon the way we approach the study of an urban system. One way of naming such entities may be by the aid of those subsystems indicated in Figure 3.1, see MAB report 31 (Unesco, 1975b). Although the literature abounds with both subtly and widely-diverging definitions of an ecosystem, the one which proves most compatible with the inclusion of the urban environment as an ecosystem is, in fact, the original definition. Here an ecosystem is regarded as an open-ended, not necessarily self-sustaining, portion of a larger system with which there may be a constant exchange, or input, of organic and inorganic materials, energy and information as well as, and including, organisms. Figure 3.1 depicts the urban ecosystem as a whole. An urban ecosystem is, of course, a dynamic system, and the preservation of its integrity requires an inward and outward flow of energy, as well as an organic circulation of numerous material, especially water.

In the urban ecosystem, non-biotic components include machines and the built environment, as well as the usual materials and processes such as water, its flow and evaporation, which are included in this category in a natural ecosystem. Also, since in urban ecosystems the human population is the most important biotic element in terms of biomass and influence on the system, the human population is shown separately from the other biotic components. Culture which, for example, includes, beliefs, ideas and laws, can have no impact on the system, nor any of its components except through the intermediary of the human population. In this sense the arrows which pass directly between culture and other components of the system reflect a certain inaccuracy. However, this convention will be retained with the expectation that the involvement of human behaviour in the interactions will be taken for granted. In the content of urban hydrology we can recognise, from Figure 3.1, that the flow of water through an urban ecosystem is effected by, and has an impact on, the non-biotic and biotic components (especially the human population component) as well as the cultural components, which include social,

political and economic subsystems.

However, there are many ways of visualising an urban area as a series of subsystems. In fact, various authors have offered classifications and diagrams showing what they consider as a systems concept of the urban region. In order to deal with such intriguing considerations, Vlachos and Flack (1974) maintain that irrespective of what the system and its subsystems are there are two major categories of interrelated parts: the physical subsystem and the

non-physical subsystem. They continue: 'Each one of these has its own subsystems, important variables, and inter-relationships. Furthermore, the urban system and its subsystem become much more complex when one introduces such intangibles as environmental amenity, quality of life, social well-being, and similar dimensions'.

The authors just mentioned also give a pictural view of their text. Figure 3.2 shows how a series of independent variables, or constraints, affect, through the particular organization of urban engineering (urban institutions), the quality of life (output) by meeting both needs of survival and needs of fulfilment (the good life). An essential point to have in mind, in discussing how well different systems represent the dynamic processes, is that the model of a system helps in understanding the interconnection of various subsystems in the total

environment. (The schematic representation shown in Figure 3.2 does not portray the situation in which there is deliberate planning for a specified future situation). A further major task is to explore how different series of constraints may hinder not only the adoption of

appropriate control system for management and operation of, for instance, runoff systems, but also a series of quite different constraints.

3.3 THE URBAN WATER MANAGEMENT SYSTEM

In the discussion at the end of the preceding section we had already entered into the concept of an urban-water management subsystem. The hydrological component of such a system is the

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energy

materials (eg water)

Figure 3.1

energy

materials (eg water) Schematic representation of an urban ecosystem

INDEPENDENT

- RATE OF URBANISATION - RESOURCES

- SIZE, SHAPE OF CITIES - STRUCTURE, ORGANIZATION

- TECHNOLOGY

J

INTERMEDIATE

URBAN HYDROLOGY

DEPENDENT

•+ QOL/SWB

INPUT THROUGHPUT OUTPUT

( REGIONAL j

LOCAL

CONSTRAINT!

RESOURCES DEMANDS SUPPORT

INFRAS TRUCTURE

URBAN INSTITUTIONS

FEEDBACK LOOP

^ >

GOODS

SERVICES

pSURVIVAL

•-FULFILMENT

Figure 3.2 System analysis concepts (QOL = Quality of life, SWB = Social well-being)