Hydrological Sciences-Journal-des Sciences Hydrologiques, 42(4) August 1997 467

Water resources for sustainable development

ZBIGNIEW W. KUNDZEWICZ Research Centre for Agricultural and Forest Environment Studies, Polish Academy of Sciences, Poznan, Poland

Abstract The significance of water availability for sustainable development is discussed. A review of water-related areas of concern in Agenda 21, the blueprint for sustainability, is offered, with particular reference to its Chapter 18 devoted to freshwater resources. The problems of water resources of vulnerable areas are tackled for the examples of arid and semiarid lands, mountains and small islands. The importance of water resources assessment and its building block, hydrological observations, for sustainable development is demonstrated and the adverse tendencies of declining hydrological observation networks are reported. Hydrological network density is seen as one of the indicators of sustainable development. Hydrological and water resources systems are perceived only as a component of the complex global system. Therefore a holistic perspective is advocated, looking at the existing inter­relationships and interfaces with other sub-systems, including social, economic, institutional, etc.

Des ressources en eau pour un développement durable Résumé On examine l'importance de la disponibilité d'eau pour un développement durable. Une revue des thèmes relatifs à l'eau de l'Agenda 21, qui constitue le schéma directeur de la durabilité, est proposée, avec une mention particulière pour son chapitre 18 consacré aux ressources en eau douce. Les problèmes des ressources en eau des régions vulnérables sont abordés dans le cas des zones arides et semi-arides, des régions montagneuses et des petites îles. On montre l'importance, en vue d'un développement durable, de l'évaluation des ressources en eau et de sa composante fondamentale, l'observation hydrologique, alors que l'on peut observer une tendance au déclin de nombreux réseaux de mesures. La densité des réseaux hydrométriques est interprétée comme un des indicateurs du développement durable. Les systèmes hydrologiques et de ressources en eau ne sont cependant que des composantes d'un système planétaire complexe. On propose donc une perspective globale, prenant en compte les interrelations et interfaces avec d'autres soussystèmes sociaux, économiques, institutionnels, etc.

INTRODUCTION

The adjective "sustainable" stems from a Latin verb "sustinere" (to uphold). The corresponding English verb, "to sustain", being in use since the late Middle Ages, has meanings such as: to maintain, to keep going, to keep in being, to keep from falling, to carry on, to withstand, to bear, to support life, to provide for life or bodily needs, to furnish with the necessities of life (Little, 1972). Many of these meanings are encapsulated in the term "sustainable development" which is being broadly used nowadays. In fact, "sustainable development" is an old concept that has been used in the management of renewable natural resources to ensure that the rate of harvesting a resource is smaller than the rate of its renewal. As mentioned in the Brundtland Report (WCED, 1987), "humanity has the ability to make development

Open for discussion until 1 February 1998

468 Zbigniew W. Kundzewicz

sustainable—to ensure that it meets the needs of the present without compromising the ability of future generations to meet their own needs". This aim should be achieved while minimizing the losses (maximizing the gains) to economic, social and environmental systems.

The availability of water in adequate quantity and quality is a necessary condition for sustainable development. Water, the basic element of the life support system of the planet, is indispensable to sustain any form of life and virtually every human activity.

The annual runoff into the oceans exceeds 40 000 km3. Withdrawals currently reaching 3800 km3 constitute only a small portion (about 9%) of the average annual runoff. At first sight this may look like a relative abundance of water. However, these apparently comforting global figures are largely misleading as far as water availability at smaller scales is concerned.

Global water consumption has increased about sevenfold since the beginning of the 20th century. This has been caused both by population growth and by increase of the per capita water use. The continuing population growth with consequences for food production and justified aspirations of nations and individuals towards better living conditions will undoubtedly cause the demand for water to grow further. An adequate and reliable supply of water of proper quality for the entire population of the Globe and for preserving the hydrological, biological and chemical functions of ecosystems is still a remote goal. The increased demand already cannot be met in a number of locations and at all times at present under the natural variabilities of temperature and precipitation.

Water shortage is therefore likely to be the most dominant water problem in the forthcoming century, jeopardizing sustainable development. The number of countries subject to water scarcity, defined as water availability below 500 m3 per capita per year, reaches 12 at present and is likely to grow to 19 by 2025 (Gleick, 1993). Some assessments foresee that the portion of the global human population subject to water scarcity may grow to 35% around the year 2025. In a number of countries subject to a dynamic population growth, a dramatic drop of the per capita availability of water has already taken place and aggravation of this process is foreseen to substantially below the level recognized now as the threshold of scarcity. The UN Water Conference in 1977 agreed that "all peoples, whatever their stage of development and their social and economic conditions, have the right to have access to drinking water in quantities and of a quality equal to their basic needs". Access to safe water has therefore become a kind of human right. The UN International Drinking Water Supply and Sanitation Decade (1981-1990) had the goal of arranging for access to safe drinking water and sanitation for the whole population of the Globe. Yet, at the end of the Decade, despite all the unquestionable achievements, a large number of human beings (of the order of one billion) still lacked clean and safe water, largely because population growth has outweighed all the progress achieved in water supply. The number of people without safe water supply has been growing up to present.

According to WHO, about 80% of all diseases and one third of all deaths in developing countries are related to water-related diseases, such as diarrhoea, malaria,

Water resources for sustainable development 469

schistosomiasis, river blindness, Guinea worm, and others which kill globally perhaps 25 000 human beings a day—over 17 people in one minute.

FRESHWATER IN AGENDA 21

The need of constraining human activities within the carrying capacity of the Earth system has been ubiquitously and unanimously accepted. Agenda 21 (UNCED, 1993) bearing the subtitle "Programme of Action for Sustainable Development", which serves as "a comprehensive blueprint for action to be taken globally", paves the way forward. Therein water resources issues are dealt with in Chapter 18 entirely devoted to freshwater resources; a number of other chapters are dedicated to several aspects of sustainable development where water components play a significant role.

In Chapter 18 of Agenda 21, seven programme areas are proposed for the freshwater sector, as given in Table 1 which also shows estimates of the average total annual expenditures that have to be borne in the time interval 1993-2000 in order to implement the proposed activities. These costs have been suggested by the Secretariat of UNCED and, as noted in Agenda 21, they are "indicative and order-of-magnitude estimates only" while actual costs and financial terms "will depend upon, inter alia, the specific strategies and programmes Governments decide upon for implementation".

Table 1 Estimated annual costs of implementation of objectives Agenda 21 (Chapter 18) in million US$ (of 1992).

Programme area

Integrated water resources development and management Water resources assessment Protection of water resources, water quality and aquatic ecosystems Drinking water supply and sanitation Water and sustainable urban development Water for sustainable food production and rural development Impacts of climate change on water resources Total for all programme areas identified in Chapter 18:

The estimated costs of implementing Agenda 21, as listed in Table 1, are given in two categories: expenditures by the international community on grant or con­cessional basis and total costs for both international and national communities. Table 1 shows that the three major expenditures are related to such programme areas as drinking water supply and sanitation, water for sustainable urban development and water for rural development/food production. Each of these objectives requires over

Costs for the international community

115

145 340

7 400 4 500 4 500

40 17 040

Total costs

355 1000

20 000 20 000 13 200

100 63 770

470 Zbigniew W. Kundzewicz

US$10 billion a year. However, it may well be that the investments in the "cheaper" water areas such as integrated water resources management and water resources assessment may have a greater leverage effect with excellent cost-benefit rates.

An estimate of the overall average annual costs of implementing all, not only water-related, areas listed in Agenda 21 in developing countries is US$600 billion including about US$125 billion on a grant and concessional basis. However, the sums really disbursed at the global level have been largely below the above estimates of the necessary costs of implementation.

Worldwide acceptance of integrated water resource management is a recent imperative. The notion is based on the perception of water as an integral part of the ecosystem, a natural resource and a social and economic good. It embraces quantity and quality aspects, surface water and groundwater, and multi-interest competing demands. It should enhance the efficiency of water use, sustainable water utilization patterns, water conservation, and wastage minimization. Rational land use and land­scape planning should play an important role in controlling water distribution, and the abatement of pollution and eutrophication of freshwater bodies.

In order to manage water in the age of scarcity, accurate assessment of the available resource is indispensable. This refers to the characteristics both of mean values and of variability, and includes water quality aspects.

It has been recognized that, since the early 1980s, hydrological data collection and analysis worldwide are not keeping pace with the actual water development and management needs, and the new demands being created by pressures for sustainable development. The largely inadequate funds available for maintenance and operation of hydrological services are being further reduced and hydrological observation networks are in decline. When confronted with budgetary cuts, it is a rare practice to strive towards an optimal reduction of a network, minimizing the information loss. More common is the elimination of an observation station which is difficult to access and expensive to run, even if loss of this station may be highly detrimental to global monitoring and to the state of our knowledge and information. Even stations where long time series of observations have been carried out may urgently require up­grading or revitalization.

The situation is particularly sensitive in conflict-prone areas where a number of countries are largely dependent on international rivers. Maintenance of good quality hydrological observation networks and arranging for data to be internationally ex­changed are imperatives.

The enhancement of collection, storage and processing of data is needed to ensure better areal coverage at the global level. This was the rationale for under­taking further multi-disciplinary large-scale research and monitoring programmes and experiments concentrated on energy and water fluxes. An increase of understanding of the availability of water is a prerequisite for the prediction of changes in the hydrological cycle and their impacts. In order to gather high quality uninterrupted streams of data on freshwater resources at the global scale, the World Hydrological Cycle Observing System (WHYCOS) is being launched jointly by the World Meteorological Organization and the World Bank (Rodda et al, 1993). WHYCOS would consist, initially, of about 1000 reference stations (hydrological observatories)

Water resources for sustainable development 471

sited on major rivers worldwide. Each station would monitor about 15 variables such as flow, water chemistry and on-bank meteorological variables, and then transmit the data through satellites to national, regional and global data centres. In WHYCOS, use will be made of those existing observing stations and data bases which meet the required specifications. Actual rehabilitation and expansion of operational monitoring and assessment programmes are being developed as regional components of WHYCOS. Those regional components are at different levels of development. Some, like MED-HYCOS in the Mediterranean Rim and SADC-HYCOS in Southern Africa, are being implemented, while others are in the planning stage.

NETWORK DENSITY AS SUSTAINABILITY INDICATOR

In Agenda 21 (UNCED, 1993), the blueprint for sustainable development, a concern was expressed that commonly used indicators do not provide adequate measures of sustainability. Chapter 40 of Agenda 21 devoted to information for decision making contains a recommendation that indicators of sustainable development "need to be developed to provide solid bases for decision making at all levels and to contribute to a self-regulating sustainability of integrated environment and development systems". In consequence, a number of endeavours have been undertaken aimed at proposing measures which could be used to quantify sustainable development. The United Nations Commission on Sustainable Development established a multi-year thematic programme on indicators.

One of candidate indicators being proposed by WMO is the density of hydro-logical networks defined as the average area served by one hydrological station (Kundzewicz, 1996). Knowledge and understanding of freshwater resources is essen­tial for sustainable development. Therefore, hydrological observations should be recognized as an essential component of sustainable water resources development.

Hydrological information on water levels, discharge, sediment and water quality is necessary for a number of projects, whereas in a particular application information on time series maxima or minima of a variable may be needed (WMO, 1994). Examples of such projects for which hydrological information is indispensable comprise water engineering works (dams, reservoirs, spillways, canals, diversions, hydropower, etc.) as well as those in the area of water quality, zoning, insurance, standards and legislation. Moreover, the availability of hydrological data in real time is needed for the management of water resources, flood forecasting and control.

Before launching a freshwater-related project, or considering forecasts and response strategies, it is essential to know how much water and of what quality has been available in the past-to-present. The basic hydrological network should therefore provide a level of hydrological information that would preclude gross mistakes in decision making related to freshwater.

Without adequate knowledge and understanding, uninformed decisions may be made. Moreover, if the hydrological cycle is not monitored with appropriate spatial and temporal coverage, decision makers and the general public may not be informed of water problems until a moment when the consequences are already severe and it is

472 Zbigniew W. Kundzewicz

late and difficult to implement effective solutions. Hydrological observations provide the basis for essential early warnings of cases where sustainable development is threatened.

The methodology used for estimating network density as an indicator of sustainable development can draw from the experience of WMO's Basic Hydrological Network Assessment Project (BNAP) (Perks et al., 1996). The objective of BNAP was to assess the adequacy of networks in a region and, more specifically, to obtain information from each country on the number of stations in their basic network, to determine actual requirements for such a network, and to prepare proposals to revise network density guidelines given in the WMO Guide to Hydrological Practices (1994). The term "basic network" was understood as principal, base, permanent stations where data have been observed continuously over a long time period.

For the purpose of responding to the BNAP questionnaire, Member countries of WMO divided their areas into "basin/administrative units" (either physical entities such as a river basin, or administrative units such as a state, or a province). Each of them, constituting a more or less hydrologically and physiographically homogeneous area, was allocated to one of the six dominating physiographic units: mountainous, interior plains, hilly/undulating, small islands (with area smaller than 500 km2), coastal and polar/arid. Information was collected on area, elevation, climate, population, total number of existing stations and number of stations the responding national agency felt necessary.

The density is understood as a set (vector) whose elements are values of densities of climatological or hydrometric observation stations for a particular hydrological variable, such as: precipitation (non-recording and recording stations); streamflow; evaporation; snow storage, groundwater; sediment; water quality (for surface water, groundwater and sediment).

The numbers of hydrological stations in operation worldwide, as reported by the WMO Member countries, are very impressive. The INFOHYDRO Manual (WMO, 1995) estimates that there are nearly 200 000 precipitation gauges operating world­wide (over three quarters of this number refers to non-recording gauges) and over 12 000 evaporation stations. At over 64 000 stations discharge is being observed, at nearly 38 000—water level, at 18 500—sediment, at over 100 000—water quality, and at over 330 000—groundwater characteristics. In fact, some specialists estimate that the last number can be even higher if specific purpose observations are also included.

Despite the apparently high global aggregate numbers of operating hydrological observation stations, the situation is not uniform, being deficient over large areas. The results of the BNAP Project (Perks et al., 1996) demonstrated that the network adequacy varies considerably, by hydrological variable, country and physiography.

The products of BNAP made it possible to update the WMO recommendations for the minimum density of hydrological observation networks. Table 2, based on Perks et al. (1996) shows a comparison of densities reported by Member countries for different physiographic units and the updated WMO minimum network density recommendations. In comparison to the WMO guidance offered in the Guide to

Water resources for sustainable development 473

Table 2 Comparison of network densities reported by WMO Member countries and the updated WMO recommendations on minimum network densities (RMD).

Non-recording precipitation BNAP (RMD)

Recording precipitation BNAP (RMD) Water temperature BNAP (RMD) Evaporation BNAP (RMD) Discharge BNAP (RMD)

Sediment BNAP (RMD)

Water quality BNAP (RMD) Groundwater BNAP (RMD)

Polar/arid

6 063 10 000

26 466 100 000 20 269 15 575

20 631 100 000 34 302 20 000 42 762

200 000 4 422

200 000 18 727

100 000

Coastal

2411 900

5 277 9 000

17 562 8 058

10 525 50 000 4 517 2 750 8 322

18 300 4 578

55 000 2 248

50 000

Hilly

2 501 575

4 977 5 075 4 976 3 704 7 783

50 000 6 104 1 875 8 165

12 500 1 982

47 500 200

50 000

Interior plains

3 957 575

12 822 5 075

18 124 10 127 22 480 50 000 9 734 1 875

13 121 12 500 11903 37 500 3 153

50 000

Mountain

3 848 250

4 548 2 050

12 556 7 370

11273 50 000 3 261 1000 5 567 6 700

5 839 20 000

1954 50 000

Small islands

2 224 25

4 479 250

6 769 4 579 3 752

50 000

6 798 300

2 481 2 000

179 6 000

54 50 000

Hydrological Practices (WMO, 1994), stricter limits have been devised for water quality observation networks for all topographies and sediment networks for polar/arid areas. Moreover, new recommendations refer also to groundwater networks.

The density of hydrological networks is an indicator illustrating the importance which is attributed in a given country to information for sustainable development. It indicates a government policy response to the need to monitor hydrological variables for assessing, developing and managing freshwater resources. Information on the density of hydrological observation networks may be viewed as one of the building blocks which form the foundation of a sound decision making procedure in the water sector, and also as an insurance which is obtained to protect against an uncertain future.

WATER RESOURCES FOR SUSTAINABILITY OF VULNERABLE AREAS

Agenda 21 (UNCED, 1993) emphasizes the sustainability of vulnerable areas, such as arid and semiarid lands suffering from frequent and severe droughts and jeopar­dized by desertification (Chapter 12), vulnerable mountainous environment (Chapter 13) and ecologically fragile small islands (Chapter 15, Area G). Water-related issues of the sustainability of these vulnerable areas are briefly discussed in the following.

474 Zbigniew W. Kundzewicz

Drought and desertification

Drought, that is a prolonged freshwater deficit, is a severe plague that humankind has suffered from the dawn of history. A combination of drought, or a sequence of droughts, and human activities may lead to desertification of vulnerable arid, semiarid and dry sub-humid areas whereby soil structure and soil fertility are degraded and bio-productive resources decrease or disappear. According to Falkenmark (1988), soil permeability and water retention capacity, which secure the infiltration of rainfall and the availability of water for an adequate production of biomass, are conditions of sustainability. Desertification affects about one sixth of the world's population and one quarter of the total land area of the world (UNCED, 1993). The extent of the problems of drought and desertification in general, and in Africa in particular, has raised a global concern. It has forced the international community to adapt the United Nations Convention to Combat Desertification, referring to "arid", "semi-arid" and "dry sub-humid" areas where "the ratio of annual precipitation to potential évapotranspiration falls within the range from 0.05 to 0.65".

Droughts and desertification have been present for a long time in Africa and the Middle East and people have interacted with these features with varying degree of success since history began. Recently, a long lasting Sub-Saharan drought, combined with demographic pressure, has dramatically accelerated the desertification process.

In order to mitigate the impacts of drought and desertification, strengthening the knowledge base of water resources is necessary (Sehmi & Kundzewicz, 1997). This embraces, first of all, the re-vitalization of networks of hydrological observing stations, reversing the tendency in the decline of networks of hydrological observing stations in Africa. The necessary data and knowledge base should extend beyond the water sciences, embracing also economic, political and social systems that are intimately inter-linked. Such socio-economic targets as eradication of poverty and illiteracy, and promoting alternative livelihood systems which may largely contribute to combating desertification, require a substantial knowledge base. Drought may trigger desertification, but human factors play a significant role (Glantz, 1994). Overcultivation, overgrazing, deforestation and poorly drained irrigation can destroy the soil at a very fast pace. It takes a long time for soil to form but only a short time for it to be destroyed. It is estimated that the present annual rate of global soil loss reaches 24 x 109 metric tons.

Without, at least, the basic scientific studies and technical evaluations of various issues pertaining to areas supporting population which suffer from desertification and drought, it will be difficult to implement any mitigating measures. A few of the burning needs are (Sehmi & Kundzewicz, 1997): (a) identification of "water points" used by communities in the areas of concern; (b) demarcating populated areas subject to damage by desertification and severe

drought; (c) carrying out statistical studies of drought duration, intensity and frequency,

starting date of drought and accumulated water deficit, and preparing maps; (d) undertaking detailed water vulnerability studies of each water point/community

Water resources for sustainable development 475

taking into account population growth, economic development level, climate change, climate variability, current and projected water use for various human activities; and

(e) drawing up a plan of action for the water sector as a basis for combating desertification and to mitigate the effects of severe droughts. The primary element of desertification is the non-availability or near-absence of

water resources. There is no doubt, therefore, that all action plans to combat drought and desertification must be geared around the possibilities of extending the availa­bility of water. Some of the technical measures of water conservation and augmenta­tion are: improved land use practices; conjunctive use of surface water and ground­water; watershed management (afforestation or reforestation, soil conservation policy, and control of grazing); rainwater/runoff harvesting; recycling water; water transfer studies; erosion control and sand dune fixation; development of water allocation strategies among competing demands. Not least, the improvement of water conservation via reduction of water not accounted for (which soars to over 60% in some places in Africa) deserve attention. Using groundwater reservoirs (aquifers) to store water when available would be more advantageous than surface water storage which is subject to very high évapotranspiration loss. There are also other human factors reducing anthropogenic pressure on the environment such as control of population dynamics, legislation, organization and education.

In order to combat desertification and promote development, a major input of financial and human resources to undertake feasibility studies is necessary. If such an input is not available, there is little hope of halting the process of desertification or mitigating the ravages caused by long droughts. The desire of several developing countries which wish to break the dependency syndrome, i.e. not to count entirely on uncertain external aid (WMO, 1995a) is worth applauding. In any case, countries themselves deploy about 90% of the resources for developing and maintaining water supply systems.

Mountains

In the advent of the 21st century, the age of growing pressure on water resources, water originating from mountains, the water towers of the Earth, particularly counts for sustainable development (Bandyopadhyay et al., 1997). It is essential for security of supply in the lowland areas, where water is being needed for a variety of uses (domestic, industrial, agricultural, navigation, fishery, recreation, etc.).

There are several important water-related issues related to sustainable development of mountainous areas, such as: watershed management to control deforestation, erosion and soil impoverishment, and reducing hazards of water-related disasters.

Mountain rivers extend their importance to an extremely large geographical area reaching far beyond the mountains. Because of the orographically enhanced precipi­tation and high runoff coefficient (due to steep slopes and low natural storage in mountainous catchments), mountains are source of a significant portion of freshwater

476 Zbigniew W. Kundzewicz

resources of the World, and feed many of the largest rivers. There are several reasons for the lack of knowledge of mountain water resources

at the global scale. Difficult access, sparse settlement with limited services (elec­tricity, telephone, etc.) and the harsh environment hinder the development of hydro-logical observations in many mountainous regions. These conditions combine to make it difficult to install and to maintain instruments that often need to be of heavy duty design, capable of withstanding harsh conditions, and functioning without regular maintenance and independent of an external energy source. Because the values of hydrological variables may range across several orders of magnitude, sensors and methods of measurement have to be specially adapted. Field studies of water resources in mountains are therefore more difficult and demanding than most other hydrological activities. The siting of gauges in mountains is also far from being satisfactory. Even if there are only very few gauges in a given mountainous basin, they are likely to be sited down in the valley, for convenience of access, rather than on slopes. This constitutes another important source of error in the assessment of precipitation (Sevruk, personal communication).

The adequacy of the density of basic hydrological observation stations based on physiography was studied in the BNAP Project of WMO (Perks et al., 1996). It was found that the WMO recommendations for minimum density (WMO, 1994; Perks et al., 1996) were not reached in 74% of mountainous basins for non-recording precipitation, 52% for recording precipitation, 65% for water temperature, evaporation and discharge, 58% for sediment and 44% for groundwater. Summarizing these numbers one can say that, for the majority of mountainous areas, the WMO recommendations on minimum network density are not met.

Recommendations on data and information activities in Chapter 13 of Agenda 21 (UNCED, 1993) devoted to managing fragile ecosystems and, in particular, to sustainable mountain development read: "governments at the appropriate level, with the support of the relevant international and regional organizations; should ... maintain and establish ... hydrological ... monitoring, analysis and capabilities that would ... encompass ... water distribution of various mountain regions of the world,... build an inventory of different forms of ... water use". Yet the practical results of implementation of these Agenda 21 recommendations are to date non­existent.

Small islands

The rise in sea level poses a threat to low lying areas which appear to be very vulnerable and sensitive to climatic change. This particularly refers to small islands in developing stages, where climate change may invoke serious disturbances in socio­economic development. Freshwater resources of coastal areas, and small islands in particular, are endangered by climate change due to the following five mechanisms: - a rise in the sea level endangers fresh groundwater sources through reduction in

island area and intrusion of saline water; - a change in rainfall amount, duration and seasonal distribution may affect the

Water resources for sustainable development All

water supplies of small islands that use rainwater harvesting systems, and groundwater recharge;

- a growth in frequency and severity of storms caused by tropical cyclones, hurricanes and typhoons may be observed due to higher sea surface tempera­tures, thus increasing the risk of flooding and storm damage, which will be exaggerated by higher sea levels;

- demand for water (for public supply and agriculture) may grow as temperature rises with the increase of levels of greenhouse gases. The demand growth induced by the climate change will be superimposed on the one resulting from the expected rise of population; and deterioration of water quality due to a decrease in the dilution of wastes discharged to surface water, groundwater and to the marine environment.

Where these changes occur together, the impact of climate change will be most severe. The need of a study of the consequence of climate change for the freshwater resources of small islands is gathering an increasing recognition. Such a study should develop a methodology for identifying and estimating impacts, apply the methodo­logy, generalize results, outline a response strategy, and indicate the needs in data and monitoring systems.

UNSUSTAINABLE POLICIES

A fair measure of sustainability of water use is the ratio of annual water withdrawals to internal renewable supplies (the use-to-resource ratio). One can define a value (e.g. 25%) which can be accepted as the lower limit of water stress. It is likely that the use-to-resource ratio will dramatically rise in some regions in the forthcoming decades (Raskin et al, 1996): it may attain in 2050 the regional values of 94% and 66% in the Middle East and in Eastern Europe, respectively.

What is a sustainable development and what is not? Typically, the border between both categories is rather fuzzy, though one can easily demonstrate examples which can be rated as unsustainable development in an unambiguous way.

An example of a clearly unsustainable case is the Aral Sea. The sea, or in fact salty lake, located in a desert where annual precipitation totals do not exceed 100 mm, is fed by two large international rivers, Syr Darya and Amu Darya, whose flow originates largely from mountainous areas. Annual runoff into the Sea dropped from 50-60 km3 in the 1950s to virtually zero in some years in the late 1970s and 1980s. Rivers ran dry because of excessive diversions of water mainly for irrigating cotton fields, that is specialized yet unsustainable agriculture. In effect, the water balance of the Aral Sea has been dramatically changed: the sea is shrinking considerably (reduction of surface area by half and of volume by two thirds in the last 30 years, and a retreat of the shoreline by as much as 120 km in some places) and its water becomes increasingly saline. This has led to further environmental problems (soil salinization, waterlogging due to inadequate flushing, and deterio­rating quality of water) in the basin of the Sea where nearly 40 million people live. The environmental disaster has caused an economic one since nearly the whole

478 Zbigniew W. Kundzewicz

national product of the five countries in the Aral Sea basin is strongly water-dependent.

A reduction of the monitoring systems in critical areas below the level of adequacy is also an unsustainable policy. Pieyns & Sehmi (1995) reported a continuous weakening of National Hydrological Services in the Aral Sea basin. The number of meteorological stations in the Amu Darya headwaters has dropped from 25 to 10 since the disintegration of the Soviet Union, and in the Syr Darya headwaters from 20 to 12. Snow measuring by helicopters has ceased and about 30 snow measuring transects have been closed. A general impoverishment of the area has also hit the dilapidating infrastructure with immense problems of ageing, failures, spare parts, etc.

As shown by Gleick (1993), there are nine countries, all in the Middle East, that now withdraw more than their annual renewable supply. They either import additional fresh water, or desalinate sea water, or pump groundwater at a rate exceeding the natural recharge rate, i.e. the renewal potential.

Libya is withdrawing 374% of its internal renewable supply (Gleick, 1993). There are abundant reserves under the Sahara Desert in Southern Libya, of the order of many tens of cubic kilometres, partially at a depth of 2000 m and more. Mining fossil water reserves, dating back to the time when the climate was wetter, at considerable depths is not a sustainable policy, as it means irreversible exploitation of a non-renewable resource.

In the light of the unsustainable policies described above, the practical question arises, as posed by Loucks (1997): should humans strive to sustain every region, every small piece of land? or alternatively, should perhaps some areas be sacrificed for the benefit of the whole? It is easy to criticize the concept of sacrifice but, as mentioned earlier, the resources for achieving sustainability of all areas of the planet are not available in any case.

Even if the consumption of non-renewable resources is considered unsustainable per definition, Loucks (1997) suggests that use of such resources may "improve technology, enhance our knowledge, create a greater degree of societal stability and harmony and contribute to our culture". Thus, there may be a number of advantages to compensate the loss of a portion of a non-renewable resource. It is not excluded that the use of a non-renewable resource may enhance the welfare of future generations thus fulfilling one of the conditions of sustainability.

CONCLUDING REMARKS

Sustainable development requires an integrated approach and a holistic perspective, in which a structure of inter-linked components is taken into account. This structure contains not only hydrological or water resources components but also a number of other components, such as environmental, economic, demographic, socio-cultural and institutional subsystems.

Institutional issues play an extremely important part in striving towards sus­tainable development. Typically, water management is fragmented among several

Water resources for sustainable development 479

institutions. At the national level, the existence of a central water office, such as a Ministry of Water Resources, that deals with all aspects of water management is very rare. Usually several ministries (e.g. environment, agriculture, forestry, industry, navigation, construction, interior, etc.) hold responsibilities for portions of water problems. Frequently the coordination between these national bodies is very limited or non-existent. The advent of strong water agencies with a clear mandate, adequate resources and technical skills is very welcome. Due to the multi-faceted nature of water issues, it is necessary, though difficult, for an agency to operate across disciplinary and jurisdictional lines.

In the WMO's survey INFOHYDRO (WMO, 1995), 175 countries reported on hydrological data collection activities. However, among the respondents there were 480 agencies, that is on average nearly three agencies per country. This illustrates the fragmentation of hydrology at the national level.

A similar fragmentation of water affairs can also be observed at the international level. There exists no powerful intergovernmental water agency. There are two dozen or so agencies of the United Nations family dealing with water. However, water units or projects in these agencies are usually outsiders, clearly beyond the mainstream.

It is proposed (UNCED, 1993) to base sustainable development on the principles of: (a) decentralization and devolution of responsibility in water and environmental matters to the parties involved at the lowest level in society (subsidiarity principle); (b) local and private sector participation; and (c) a demand-driven cost recovery approach and equitable charging to enhance sustainability and enforceable legislation at all levels. Further, it is essential to reach significant portions of communities and involve them in the process of consultation to make them understand, accept and support plans. The principles of decentralization and involvement of communities pose ambitious challenges for education and training.

Agenda 21 (UNCED, 1993) proposes that sustainability be built into national accounting. Nations should set priorities and construct implementation plans for sustainable development.

Water is not a free good any more but rather an economic good. A change of philosophy is needed; rather than trying to fulfil increasing water demands and devise new costly supply sources, one should strive towards increasing the efficiency of water use, trying to "do more with less".

There is still much to achieve in the area of water demand management. Water pricing is likely to be increasingly important, covering not only the cost of development and water supply but also the cost of resource, in the sense of foregone opportunities. Tradeable water permits offer another mechanism.

There are several cases when the recent behaviour of time series of hydrological variables differs significantly from the historical means. To a large extent this has been caused by direct anthropogenic reasons—human activities like deforestation, urbanization, etc. However, many scientists attribute a part of these changes to man-induced nonstationarity of the natural climatic system; to climate variability and change (greenhouse effect). For example, decreases of precipitation and water levels in a number of rivers and lakes in Africa have been observed. An increasing severity

480 Zbigniew W. Kundzewicz

of extreme events has been reported, with such examples as the recent floods on the Mississippi and on the Rhine. Some experts explain the above observations by such physical mechanisms as changes of prevailing atmospheric circulation patterns and of directions of atmospheric moisture advection. The possibility of climate change may add another dimension to the context of sustainable development.

Acknowledgements Sincere thanks are due to colleagues in the Hydrology and Water Resources Department of the World Meteorological Organization for their interactions and collaboration in 1993-1997.

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