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Michael Acreman, Freshwater Management Adviser to the IUCN, Institute of Hydrology, United Kingdom
Water is the lifeblood of our planet. It is fundamental to the biochemistry of all living organisms. The planet's ecosystems are linked and maintained by water, and it drives plant growth, provides a permanent habitat for many species (such as 8,500 species of fish), and is a breeding ground or temporary home for others, including most of the worlds 4,200 species of amphibians and reptiles described so far. Water is also a universal solvent and provides the major pathway for the flow of sediment, nutrients and pollutants. Through erosion, transportation and deposition by rivers, glaciers, and icesheets, water shapes the landscape and through evaporation it drives the energy exchange between land and the atmosphere, thus controlling the Earth's climate.
Apart from a few minor chemical processes, water is neither created nor destroyed, it only moves from place to place and changes in quality. The total amount of water on Earth is 1.4 billion cubic kilometers (km3), but only around 41,000 km3 circulates through the hydrological cycle, the remaining being stored for long periods in the oceans, ice caps and aquifers. Furthermore, the renewal rate provided by rainfall varies around the world. In the Atacama desert in southern Peru it almost never rains, whilst 6,000 millimeters (mm) of rain per year is not uncommon in parts of New Zealand. In any one place rainfall also varies from year to year. In the early 1980's the world witnessed tragic scenes of drought and starvation in the Sahel, but by August 1988 floods ravaged the same region. Water availability also varies over a longer time scale. Some 10,000-20,000 years ago, during glacial phases in high latitudes, rainfall over the current Sahara desert and Middle East was much higher and percolation of water to underlying rocks led to the build up of substantial groundwater resources (Goudie, 1977). However, the recent drier climate in these regions means that recharge is much reduced and groundwater exploited is not being replaced at the same rate. Superimposed upon natural climate cycles are human induced global changes. The consensus is that during the next century global temperatures will rise by about 0.2 Centigrade per decade (IPCC, 1996), with some areas exceeding this rate and some areas cooling. However, it is uncertain how this will affect water resources. Evaporation is likely to rise, but changes in rainfall patterns are less easy to predict. However, it is feared that many areas will become drier and that floods and droughts may become more frequent and more extreme.
The 20th century has witnessed unprecedented rises in human populations, from 2.8 billion in 1955 to 5.3 billion in 1990 and is expected to reach between 7.9 and 9.1 billion by 2025 (Engelman and LeRoy, 1993). Consequently, human demands for water, for domestic, industrial and agricultural purposes, are also increasing rapidly. The amount of water that people use varies, but tends to rise with living standards. In the United States, each individual typically uses 700 liters per day for domestic tasks (drinking, cooking and washing), whilst in Senegal, the average use is 29 liters per day. In general, 100 liters per person per day is considered a minimum threshold (Falkenmark and Widstrand, 1992) for personal use. However, when agricultural and industrial uses are included, countries with less than 1,700 cubic meters (m3) per person per year (about 4,600 liters per day) are considered to experience water stress, those with less than 1,000 m3, water scarcity (World Bank, 1992). Because of the spatial mismatch between water resources and people, it is predicted that by 2000, (using the African continent as an example) twelve African countries, with a total population of approximately 250 million will suffer severe water stress. A further ten African countries will be similarly stressed by the year 2025 containing some 1.1 billion people, or two thirds of Africa's population, while four (Kenya, Rwanda, Burundi and Malawi) will be facing an extreme water crisis (Falkenmark, 1989).
With such a water crisis facing many countries, it seems an immense task just to manage water so that there is enough for people to drink, let alone enough for agricultural, environmental, and industrial uses. The situation is often presented as a conflict of competing demand, as though it was a matter of choice, say, between water for people, or for wildlife, or for the environment.
The Brundtland Report, Our Common Future, and the United Nations Conference on Environment and Development (UNCED) in Rio in 1992 seemed to mark a turning point in modern thinking. A central principle of Agenda 21 and of Caring for the Earth (IUCN/UNEP/WWF, 1991) is that the lives of people and the environment are profoundly inter-linked. Ecological processes keep the planet fit for life, providing our food, air to breathe, medicines, and much of what we call "quality of life." The immense biological, chemical and physical diversity of the Earth form the essential building blocks of the ecosystem. Thus whilst people need access to water directly to drink, providing water to the environment means using water indirectly for people. This concept is so basic that it has permeated all aspects of water resource management, such as the new water law of South Africa, whose Ninth Principle states that: "the quantity, quality and reliability of water required to maintain the ecological functions on which humans depend shall be reserved so that the human use of water does not individually or cumulatively compromise the long term sustainability of aquatic and associated ecosystems."
More attention needs to be given to the role of natural ecosystems in managing the hydrological cycle and their potential as alternatives to major engineering works. As an example, well managed headwater grasslands and forests reduce runoff during wet periods, increase infiltration to the soil and aquifers and reduce erosion, such as sustaining flows during drought periods and reducing runoff during floods. Conserving wetlands in particular, by ensuring that they have adequate supplies of water to maintain their functioning, can be a positive benefit to humanity. Many wetlands provide important fisheries, arable and pasture land, fuelwood and medicines as well as habitats for wildlife. Some wetlands also perform many important natural hydrological functions including flooding reduction, water quality improvement (by removing pollutants) and groundwater recharge. Thus for the millions of people worldwide who depend directly on wetland resources or benefit from wetland functions, providing water for the environment and for people are one and the same.
In preparation for the IUCN/PRB/US-AID workshop on "Water and Population Dynamics" which was held at the IUCN's World Conservation Congress in Montreal, October 1996, I presented some ideas to stimulate discussion and to provide a framework for examples of water and population dynamics from around the world. These are presented as a list in Box 1 and explained more fully below. It is not presupposed that this is a definitive list, but it nevertheless captures many issues that must be addressed if water is to be managed sustainably for people and the environment.
|Box 1. Ten Principles of Water Management for People and the Environment|
1. Value water
2. Use water sustainably
3. Develop suitable institutions to manage water
4. Collect and disseminate information
5. Maintain a social and cultural perspective
6. Ensure equitable access to water
7. Use appropriate technology
8. Try to solve causes not symptoms (but accept practical solutions)
9. Take an ecosystem approach
10. Work as multidisciplinary teams
To decide on the best use of water, an independent measure of benefits of various alternative options is required (Barbier et al, 1997). Monetary value is frequently employed as this is how most goods and services are exchanged in everyday life. The aim is to allocate water to those uses that yield an overall net gain to society, as measured in terms of the economic benefits of each use, less its costs. This is termed economic efficiency. In northern Nigeria, large dams were constructed on the Hadejia River to feed intensive irrigation, which led to a reduction in the Hadejia-Nguru wetlands downstream (Hollis et al, 1995). Barbier et al (1991) demonstrated that the economic value of water when used for intensive irrigation was many times less than its value for supporting fisheries, agriculture and fuelwood in the wetlands downstream (Table 1). Consequently, the Nigerian government is now exploring the potential for releasing water from the dams to restore the wetlands. Economic valuation thus provided a sound basis for water management decision making.
Economic valuation is, however, not a panacea for decision-makers facing difficult choices. One problem is that who actually gains and who loses from a particular water management scheme is not part of the efficiency criterion per se. These distributional effects may be very important since although the scheme may show a substantial net benefit and would be deemed highly desirable in efficiency terms, the principal beneficiaries may not necessarily be the ones who bear the burden of the costs, or suffer any adverse impacts which arise. Kariba dam was the first of the major dams in Africa, built in 1959 and had a great benefit to Zambia, as it supplied power for copper mining. However, since no plans for rural electrification were made, the 50,000 Batongans displaced by the reservoir bore the burden of the costs, but saw no benefit (Acreman, 1996).
A further difficulty facing valuation of water is insufficient information on ecological and hydrological processes, such as the nutrient recycling or groundwater recharge function of wetlands. If this information is lacking, considerable investment of time, resources and effort in further scientific and economic research is required.
Finally, some members of society may argue that certain environmental systems, such as a tropical rainforest, may have an additional 'preeminent' value in itself beyond what it can provide in terms of satisfying human preferences, particularly when water management may lead to the degradation of essential (life-support) functions of ecosystems, such as nutrient cycling or loss, or decline, of rare species. From this perspective conserving an ecosystem or species is a matter of moral obligation rather than efficient or even fair allocation of the water. Thus, economic values represent just one input into water management decision-making, alongside other important considerations.
When water resources are used at a rate greater than they are being replenished, the resource will decline and the usage becomes unsustainable. In many areas of the world, for example, groundwater is being extracted from the underlying aquifer more rapidly than it is being replenished. Around Quetta in Pakistan, where the abstraction rate is 2.5 cubic meters per second(cumecs), whilst the recharge rate is 2.0 cumecs, the groundwater level is falling at around one meter per year (Acreman, 1993). Furthermore, the problem is likely to worsen as the population is growing at seven percent per year (i.e. a doubling in ten to 11 years). In some areas of Libya, no recharge currently occurs, the sustainable use rate is zero and thus the water is effectively being mined. Even where groundwater abstraction might be reduced to equal the recharge, the groundwater levels have often been lowered to a point where key ecosystems have been destroyed. For example, pumping of the aquifer to supply the rapidly expanding population of Amman in Jordan has led to degradation of the Azraq oasis (Fariz and Hatough-Bouran, this volume). Similarly, intensive use for irrigated agriculture of the water from aquifers underlying the upper Guadiana river basin in central Spain (Figure 1) has resulted in almost complete and irreversible destruction of the Tablas de Daimiel wetlands (Llamas, 1988). Part of the problem is that planning has often taken place by deciding first how much water is needed and then trying to find a source. In contrast, the opposite process is likely to lead to more sustainable water use, by first assessing the available water resource and then deciding how best it can be used.
There are many ways in which water can be used more sustainably:
Institutions at various levels are essential for equitable allocation of water. At the global level two initiatives are currently underway, first the World Water Council, that aims to assess global water resources and policy issues, and second the Global Water Partnership, which has proposed coordination of large scale programs on water and sanitation, agriculture and irrigation. For some international river basins, a special management authority has been established. OMVS (Organisation pour la mise en valeur du fleuve SÈnÈgal) has defined a water sharing agreement for the Senegal River between Mali, Mauritania and Senegal. This includes water for river navigation, irrigation, hydropower generation and, currently, artificial flood releases to maintain the traditional agriculture of the riparian wetlands, although the best allocation between the uses is hotly disputed (Horowitz and Salam-Murdock, 1990; Hollis, 1996). Mpande and Tawanda (this volume) argue for the establishment of a regional water management commission for the Zambezi basin, which includes parts of eight southern Africa countries. This is required to avoid future conflicts over water resources, where the average population growth is three percent per year (a doubling in 22 years) and the demand for domestic, agricultural and industrial water use is rising rapidly.
Effective institutions are also required at national, provincial and local level, to ensure that all stakeholders can contribute to the decision making process. A good example is provided by the Pongolo River in northeast South Africa near its borders with Swaziland and Mozambique (Breuwer et al, 1996), where a dam was constructed in the late 1960s to irrigate agricultural land for white settlers. In the event, no settlers came to use the irrigation scheme. The dam changed the whole flooding regime of the river which led to crop failure on a massive scale downstream. In 1978 a workshop led to a plan for controlled releases to rehabilitate the indigenous agricultural system and the wildlife. However, initial releases of water from the dam were made at the wrong time of the year and crops were either washed away or rotted (Poultney, 1992). In 1987 the Department of Water Affairs and the tribal authorities agreed to experiment with community participation. As a result, water committees were established, representing five user groups: fishermen, livestock keepers, women, and health workers (both modern primary health care workers and traditional herbalists and diviners), and were given the mandate to decide when flood waters should be released. These committees were very successful at carrying out people's views and have led to management of the river basin to the benefit of the floodplain users. This is a unique example of where floodplain users are participating directly in the decision making process and influencing development and management of the river basin.
Whatever the level, institutions need well-informed members who have an appreciation of the wide range of issues facing water resource allocation. Training is an essential element, but training needs vary with the type of institution. Professional technical advisors require formal training courses, for example, on water resource planning and wetland management, whilst local community representatives may be best trained with involvement in local activities, such as participatory rural appraisal or through visits to demonstration projects (see the example from Tumkur District, India by Kumar et al, this volume).
One factor that may severely limit the effectiveness of community involvement in the management process is mistrust or misconception their concerns and aspirations are not recognized or properly understood (Smith, 1995). The rather nebulous term "general public" is often used by the managing authority to define everyone else, which implies an "us and them" attitude. If "general public" is replaced with "local community," "they" become land owners, resource users and individuals with a direct and personal association with river, lake or wetland. More importantly, professionals will wish to see themselves as part of that community and mutual understanding may become easier to achieve.
Effective management of resources can only be achieved if decisions are based on sound information. Even in a country like the UK, where there are over 1,000 river flow measurement stations, the quantity of available water resources is still uncertain and considerable funds are being invested to develop methods of resource assessment for ungauged rivers (Gustard et al, 1992). Furthermore, hydrological measurements on slow flowing or static water bodies, such as fens and marshes, are very rare (Acreman and Hollis, 1996). In many countries, not even main rivers are monitored effectively, which means that the true water resource is largely unknown and effective planning and management are little more than shots in the dark. Likewise, levels of water use, such as for irrigation, are not known precisely. Thus, in few countries is it possible to base demand management strategies on accurate data. In times of economic difficulty, data collection and research are often the first activities to be cut. In contrast, hydrological data collection needs to be expanded to cover more rivers, wetlands and aquifers, both in terms of water quantity and quality. Better models are required to make predictions, particularly since our climate is likely to change substantially over the next 50 years. Furthermore, tests of models and management strategies are required to see which are applicable under different circumstances. Forecasting of floods and droughts requires new initiatives and development of communication systems, such as the World Hydrological Climate Observation System, known as WHYCOS, which will collect hydrological information in real-time via satellite from throughout the world (WMO, 1995).
In many countries hydrological data are collected and analyzed and presented in hydrological year books (Figure 3). However, these are often not well distributed and in practice are only available to certain government departments and their consultants. Information on water resources and population needs presented in a concise and easily understandable manner and widely disseminated to a wide range of government officials, researchers and local communities so that they are all able to participate in decision making process. Summaries of the local or regional water resource situation should be supported by details of water management options and visits to demonstration projects and other institutions facing similar resource shortages.
Communication and dissemination of information needs careful planning. Whilst a raw data file on diskette may be appropriate for transferring information to a university researcher, local communities need to receive their information through easily understandable brochures, newspaper articles, radio broadcasts and public meetings. Policy makers need short summary documents with ample charts and simple tables. Thus a range of media need to be employed to disseminate the information need for different actors to play a useful role in discussion and decision making.
Water is such a fundamental part of lives and is interwoven into the fabric of our societies. For example, the Christian faith welcomes new members through baptism, where water symbolizes cleansing the soul and nourishing the body. Many Hindus believe the River Ganges is sacred: a dip in it will purify the soul and scattering the ashes of cremated body on the water will aid rebirth in a higher existence. Management and allocation of water are thus particularly sensitive issues. Unlike other resources such as coal or timber, ownership is not accepted in the same way, partly because water is dynamic, flowing through the environment and perceived as "God-given." Proposals to charge money for water supply are often met with hostile reactions, even though it can be argued that the costs are related to the infrastructure and its maintenance rather than the water itself. Thus, although water pricing may be theoretically a sound demand management strategy, its implementation is frequently not acceptable.
Water recycling is another notion promoted above. However, some regions believe that it is not acceptable to reuse water that has passed through a human body. In many developing countries women and children in particular walk long distances to collect water. Clearly, providing more convenient wells improves their well-being. However some water supply projects in Africa installed taps in houses, which resulted in depression and other social problems because going out of the house to collect water and do washing was an important social event where women would meet and chat.
Rivers, lakes and their wetlands are part of the cultural history of early people being a central element of mythology, art and religion. The Marsh Arabs of southern Iraq have lived for centuries on artificial islands in the marshes at the confluence of the Tigris and Euphrates rivers. Their lives have been very much in harmony with the wetlands and they have had a spiritual connection which is somehow different from the direct use of wetland products for boats building and houses construction. However, diversion of water upstream has led to desiccation of the marshes and seriously threatens this 5,000 year old culture. The Somerset Levels wetlands of the UK are also important for their cultural heritage. Here fewer people depend directly on the wetlands for their livelihood, but they are no less a fundamental part of life for local people. Also people who have moved away from the area and live in a town hold pleasant memories of life in the wetland. Because of these strong links to water, it is difficult to derive an economic value for this use of water, and techniques such as asking people how much they would need to receive in compensation for destruction of a wetland are not well received. Thus, whilst scientific approach to water management has many advantages, decision making needs to take account of ethical, aesthetic and religious values.
Water resource statistics are often provided on a per capita basis. This represents an average across the entire population, giving the impression of equality in the availability of the resource, i.e. equal access and equal ability to pay (if charged for). The contrast in access is strikingly evident in many developing countries. In the city of Quetta, Pakistan, some rich residents have private boreholes which they use for filling their swimming pools and washing their cars, whilst 50 meters away the poor take their water from muddy pools. Furthermore, several studies have shown that the urban poor pay higher prices and spend proportionally more of their income on water. In Port-au-Prince, Haiti, the poorest households can spend 20 percent of their income on water; in Onitsha, Nigeria, the poor pay 18 percent whilst the upper income households pay two percent. In Jakarta, Indonesia, 32 percent buy water from street vendors at US$1.5 to US$5.2 per cubic meter, sometimes paying 25 to 50 times more than the 14 percent of households who receive water from the municipal system (World Bank, 1993).
In addition, the burden of insufficient water quantity of quality for domestic use is likely to be borne disproportionately by women and children. Because they are the primary water collectors, longer collection times mean that women have less time for agricultural production and less time for child care. Water is vital to women for many small scale food processing or craft activities, which are important sources of income (Serageldin, 1995). Women are also the main care providers, thus sickness in the family due to contaminated water impacts them more severely than men.
Problems of access to water and land in the Kafue Flats (Chabwela and Mumba) are more subtle, but just as critical. The Kafue and Itezhitezhi dams, which control water availability on the wetlands, are managed by the Zambian Electricity Supply Corporation to maximize hydroelectric power output. This has altered the flow regime of the river, reduced flooding and adversely affecting the fish stocks available to subsistence producers. Much of the traditional grazing land that is still flooded has been designated as a national park, thus local herders have been forced out and now overgraze the remaining areas.
Kumar et al show how access to water in Tumkur District, India, has been affected by the switch from gravity fed tank and canal irrigation, from which all farmers benefited, to boreholes driven by electric pumps which benefit only farmers with sufficient capital to sink a borehole. The subsidy on electricity for pumps has led to a vicious spiral of unsustainable pumping leading to lowering of groundwater levels which has resulted in increased reliance on pumps. As water is so fundamental to life, inequitable allocation of water is a sensitive subject. Nizamani et al (this volume) reports how, in 1992, a local community-based organization (CBO) took the irrigation department to the human rights court on the basis that corrupt officials were accepting bribes from wealthy farmers in the head areas to increase their irrigation flows. This had led to reduced flows in the tail area, increased salinization of crop and drinking water and migration of 8,000-10,000 people from 38 villages. Although the CBO won the case, not all of the migrants returned to the area.
Where water resources cross provincial or national borders, downstream users may be denied access to water by hydrological management upstream. The Farakka Barrage, constructed in 1974, on the Ganges in India, a few kilometers upstream of the border with Bangladesh, has reduced flows downstream by one half (Rashid and Kabir). Dry season flows are particularly important to flush sediments, sustain fisheries and prevent sea-water incursion, and their reduction leads to saline soils and groundwater, affecting some 20 million people. The Sunderbans mangrove ecosystem, on which some 500,000 people and a unique ecology depend, is also being degraded as freshwater flows are diminished.
Many water resource schemes in developing countries were conceived, designed and implemented from a developed country view point. Until the 1970s, one of the main underlying philosophies was the need to control nature. Technology was seen as the means to bring order to the vagaries of the world's climate. For example, dams are used to store water during rainy periods and release it when needed during the dry season for industry, agriculture or power generation. This is particularly important on rivers with seasonally varying flows. Climate extremes, such as floods, were seen as wholly negative and there was little appreciation of the central role that floods have played for many centuries in the rural economy of many developing countries. The inundation of floodplains provides a breeding ground for large numbers of fish and brings essential moisture and nutrients to the soil, supporting, for example, gallery forests and essential dry season grazing for migrant herds. As an alternative to large river engineering schemes, the Hadejia-Nguru Wetlands Conservation Project in Nigeria, for example, has promoted improved local water management within the wetlands, with the construction of small embankments and simple wooden sluice gates. The wooden gate can be replaced by wire mesh screens to allow water into fields whilst keeping out fish, which eat the young rice shoots, until the plants have become established.
This example highlights the need to make use of traditional technology which has developed over many years, often in concert with the environment rather than against it. In contrast to many large, modern, intensive irrigation schemes, that have been shown to be unsustainable, the Mayan people of Central America developed irrigation canals and raised fields (chinampas) that sustained their civilization for many centuries (Barrientos and Fern·ndez, this volume). Small earth dams have been beneficial in arid areas of Pakistan, encouraging groundwater recharge (if sited over permeable rocks) and trapping sediment which can be cultivated in situ or excavated to fertilize surrounding agricultural land. Throughout west Asia, much water is stored in alluvial cones at the base of steep impermeable slopes. This has been exploited traditionally by the excavation of tunnels, from the alluvium downslope towards the villages or agricultural land, with vertical shafts every few hundred meters to provide water abstraction points (Figure 4). Many of these have now fallen into disrepair and replaced by boreholes directly into deeper aquifers powered by electric pumps, which have permitted over-exploitation of the groundwater.
Whilst technology has clearly brought benefits to many people, to be sustainable it must be appropriate in terms of the ability of local people to maintain the system and appropriate for the environment, as far as possible working in sympathy with it, rather than just against it.
With many environmental, social, health or economic problems, it is easier to locate and treat the symptoms rather than the cause. As part of the development of the Senegal River basin the Diama barrage was built across the river mouth. This allowed its use for irrigation, since periods of saline water intrusion into the river, which used to occur during the dry season, were replaced by a regime of continuous freshwater. This also led to increased survival of snails and mosquitoes which carry diseases. Before 1987 Rift Valley fever (a mosquito-borne viral disease) had never been recorded in West Africa and human intestinal schistosomiasis (an aquatic snail-borne worm parasite disease) was little recorded. Following construction of the Diama dam 200 human deaths from Rift Valley fever were recorded along with an 80 percent abortion rate among sheep and goats. In 1988, there was a two percent prevalence rate of schistosomiasis, by 1989 this had risen to 72 percent (Verhoef, 1996). The traditional approach to disease control has been to spray chemicals to control the mosquitoes and to inoculate local people. This clearly treats the symptom rather than the cause. However, the World Health Organization's Panel of Experts on Environmental Management (PEEM) is now promoting environmental management as a health control measure which treats the cause. In the case of the Senegal valley this might mean allowing irrigation areas to dry out or allowing saline water into the river periodically to mimic the natural system.
In many cases the cause of a problem may be apparent, such as increase in population putting stress on environmental resources. The River Pang in central southern England was declared one of the 40 worst affected rivers in the UK due to pumping of water from the underlying chalk aquifer that had increased since the mid 1960s for public supply. As a result the upper reaches of the Pang dried up more frequently and for longer periods than would normally be expected and the middle and lower reaches became shallow and sluggish. In 1992 pumping was reduced by exploiting a new groundwater source and a rise in the groundwater level occurred (Figure 5). This, combined with high rainfall, resulted in flows returning to the upper reaches. However, such simple solutions are not always available and most are fraught with political, cultural or practical difficulties. It is therefore important to be pragmatic and to seek reasonable solutions. The restoration of the Azraq Oasis, a groundwater-fed wetland, in Jordan (Fariz and Hatough-Bouran, this volume) provides an excellent example. Intensive pumping of the aquifer to supply the rapidly expanding population of Jordan, and its capital Amman in particular, led to desiccation of the wetland. The cause of this problem is the rising population and its increasing demand for water, for domestic, agricultural and industrial uses. In the long term this might be addressed by, for example, recycling of water, demand management, family planning and desalinization. However, immediate action was required to save the functions and values of the Azraq oasis. A practical temporary solution was agreed where water is now pumped back to Azraq, which has revitalized the wetland.
The Dublin Statement (ICWE, 1992), which preceded the UNCED Conference in Rio, states that "since water sustains all life, effective management of water resources demands a holistic approach, linking social and economic development with protection of natural ecosystems." There is a need to develop a broad-based approach to water management, with greater emphasis on integrated regional planning and conservation of critical habitats. The environment is composed of a set of physical, chemical and biological components, including water, oxygen, plants, animals, soils, minerals. Each plays an important role either providing structure, such as rocks, or through interaction with other components, maintains crucial processes, such as energy flow or nutrient cycling. Superimposed on this natural environment is the effect of human beings. There is no place on earth unaffected by human beings, who have had large scale impacts on the earth's environment ever since agriculture began thousands of years ago. The ecosystem management approach aims to integrate all the important physical, chemical and biological components and processes which interact with social, economic and institutional factors. This requires integrated management of mountains, drylands, forests, agriculture, housing, industry, transport, waste disposal, aquifers, rivers, lakes, wetlands and anything which has an effect on the environment (Figure 6). The appropriate management scale depends upon the relative importance of the components in the system. The fundamental unit for water issues is normally the drainage basin, as this demarcates a hydrological system, in which components and processes are linked by water movement. Deforestation of headwater catchments can, for example, affect water yield and frequency of flooding downstream (Newson, 1992). Hence the term integrated river basin management has developed as a broad concept which takes a holistic approach. However, frequently the underlying aquifer does not coincide with the surface river basin. Thus, where groundwater plays a significant role, a group of basins overlying the aquifer may constitute the appropriate unit of water resource management. For issues where air quality is influential, such as acid rain, the "airshed" (as opposed to the watershed) will be more appropriate implying the integrated management of source areas, which may be industries in the UK, with affected areas in Scandinavia.
An ecosystem approach, through integrated river basin management aims to make the sustainable use of resources within a river basin. Once the scientific basis for management options has been defined by professional staff, the participation of local communities, farmers, industry and conservation organizations is needed to satisfy the needs of different interest groups. Successful integrated management frequently begins with studies of the interactions between various natural components of the drainage basin and the role of specific ecosystems. N'Djim and Doumbia (this volume), for example, report on the effects of deforestation (mainly for fuelwood) and overgrazing of marginal drylands on the hydrological cycle, reducing the infiltration of rain to the soil and increasing the severity of droughts. This exemplifies the need to link land use and hydrogeochemical processes in drainage basin studies.
Most river basins contain a variety of landscapes, land uses, habitats, industry, communities, laws and traditions. Thus, implementation of a truly integrated ecosystem approach as proposed above, requires the establishment of interdisciplinary teams including hydrologists, water engineers, biologists, physicists, soil scientists, planners, human and animal health experts, ecologists, sociologists, demographers, legal experts, and agro-foresters. These teams need to address a wide range of sectoral topics including population dynamics, water quality modeling, irrigation, health problems, water weeds, fish, herding, legislation, training, and participatory rural appraisal. In addition there will be many cross-sectoral issues, such as development of a geographical information system to overlay various spatial data sets, equitable allocation of resources, development of community participation in resource management, establishment and running of authorities to coordinate planning and management. Conventionally, different disciplines tend to be specialize in separate sectors, for example, hydrologists and fisheries experts often belong to different ministries between which there is little formal contact. Each sector often has its own agencies and authorities responsible for development, many of which relate to water issues. Given the interconnection of the ecosystem, it is critical that inter-sector, interagency collaboration is established to develop the multidisciplinary team. Indeed, ecosystem management accepts that no individual or agency can cover all the different aspects involved. The various agencies should collaborate on all aspects of planning and implementation of projects, including problem analysis, project design, data collection, analysis and modeling, policy development, management and enforcement, monitoring and evaluation.
The Earth is shared by people and a range of plants and animals which is so wide that not all species have been, or ever will be, identified, or their functions understood. Despite the lack of detailed knowledge, it is clear that each of the physical, biological and chemical components of the Earth plays an important role in its structure and function. Furthermore, water is essential to people, plants and animals alike. Water management has traditionally been focused on providing enough for people to drink, grow their food and support their industries. Providing water to the "environment" is often viewed as a luxury which only rich countries can afford. As the world's population rises, there will be increasing demand to ensure that direct supply of water to the human race is given top priority. However, people cannot live by water alone and require the services of environment's life support system, which itself needs water to function. Sound water management should, therefore, focus on the global ecosystem and not as a conflict against nature to supply water for people. Mutual survival of people and the environment means that the ten principles of water management must be followed. Water must be: valued; used sustainably; administered by suitable institutions; viewed through a social and cultural perspective; equally accessible to all; developed through the use of appropriate technology; cared for by treating the causes of problems and not just their symptoms; managed through an ecosystem approach; and dealt with by multidisciplinary teams which collect and disseminate a wide range of information to produce sound decision making.
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