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close this bookDiversity, Globalization, and the Ways of Nature (IDRC, 1995, 234 p.)
close this folder7. Managing planetary thirst
View the documentSome basic facts
View the documentWater supply and options
View the documentThe demand side of the issue
View the documentWater issues throughout the world

Some basic facts

Most of the world’s water is stored in the oceans (97.39%) and in glaciers and ice sheets (2.01%). A large part of the remainder is contained in geological formations (0.54%). Only about 0.06% occurs as surface water, of which more than half is salty, making it unpotable. Therefore, available fresh water constitutes less than 0.02% of the hydrosphere. Of surface fresh water, 95% is stored in lakes. Flowing water represents only about 0.001% of the water on the planet (Bethemont 1980). However, this volume of flowing water is more than enough to satisfy all human needs now and in the near future.

Every year, 496 thousand cubic kilometres of water falls as precipitation - that is about 100 thousand cubic metres per person per year. If the annual precipitation was spread evenly over the planet, it would amount to about 973 millimetres. However, only 25% of this total falls on the continents. Asia receives the most (28%), despite its low average precipitation of 696 millimetres per year. South America, with less than half the area, receives almost as much (25%) because of its higher average precipitation (I 564 millimetres per year). Africa’s average precipitation is similar to Asia’s; North America’s is slightly lower (645 millimetres per year). Assuming that the volume of stored groundwater is unchanged, the volume of water lost to evaporation from the land masses is as high as 84% of the total precipitation in Africa, 67% in Australia, and 62% in North America. In Asia and South America, evaporation loss accounts for 60% of the fallen water; in Europe, 57%. Only in Antarctica is the rate considerably smaller at 17%.

If we restrict our calculations to precipitation falling on the continents and subtract the amount lost to evaporation (about 60%), over 80 thousand cubic metres would be available for each person annually. Per-capita need varies from place to place, but generally does not exceed I cubic metre per day. These figures show that availability of water for human use does not relate to its volume. Rather, it depends on many other factors that we identify and characterize in this chapter.

Hydrographic basins

Hydrographic basins are natural units made up of the various terrestrial environments through which water moves toward a given outlet. In that sense, hydrographic basins can be defined as the upstream territories of a lake or stream. Basins are complex; they include both surface and underground water. These two categories of water are closely interrelated and must be considered together. The main components of a typical basin are watersheds, a hydrographic network, and groundwater systems.

The three parts of a hydrographic basin are interconnected: watersheds receive precipitation, which infiltrates groundwater systems or flows toward valleys, forming streams. Part of the groundwater can go back into the streams, and water from the streambeds often recharges the underlying aquifers. Some water may reenter the atmosphere through evaporation and fall again on the watershed, closing the cycle. By and large, however, the system is open because most basins exit toward the sea or other major water body. The outlet of the basin is also an outlet for sediments, dissolved salts, and contaminants.

The geomorphic water cycle

Surface waters may occur in a complex array of hydrologic features and systems, including streams, lakes, swamps, and other flowing or lentic water bodies. Surface water bodies are fed from three main sources: instantaneously from rainstorms and subsequent runoff; from springs (groundwater discharge); and from the melting of ice and snow.

In tropical and temperate arid climates, streams are mainly fed through runoff. Precipitation falls on bare soils, little or no infiltration occurs, and the water flows downhill into river valleys. Rivers in arid areas have irregular flow patterns and may suffer catastrophic floods and droughts. In humid climates, the opposite occurs. Soils are covered by vegetation, and rainwater is intercepted by leaves and branches. Most of the water evaporates or infiltrates the soil and only a small fraction remains as surface runoff. Underground, the water moves through geological formations, reappearing as springs next to streams, lakes, or swamps.

Thus, in humid climates most of the water comes from springs, whereas in arid areas the supply of water to the natural surface systems is related to runoff processes. In addition, as a result of higher evaporation rates and the presence of salts in the soil, water in arid climates tends to contain a higher concentration of dissolved solids; in humid environ’ meets the opposite is true.

Difficulty of managing international hydrographic basins

Hydrographic basins, both on the surface and underground, do not respect national boundaries; nor are national borders arranged around water systems. The sharing of water resources is common throughout the world. In some cases, conflicts may develop, and water issues may become important factors in international politics.

Some hydrographic basins, even a few large ones, are mainly or entirely within a single country; for example, the Yangtze River in China and the Mississippi River in the United States. Hydrographic basins are more frequently shared by two or more countries, however, making agreement on management strategies difficult.

Water supply and options

Despite the enormous volume of fresh water that circulates through the continents annually - easily enough to satisfy the needs of humankind for centuries - many people around the world do not have access to this vital liquid. There are several reasons for this. First, although water is abundant, fresh water only exists in large volumes in small areas of the planet (the lower reaches of rivers, large lakes, and high-yield aquifers). Second, available fresh water is not always fit for human consumption, sometimes because of natural causes, but more often as a result of anthropogenic degradation. Third, not all water sources are renewed at a sufficiently high rate to be suitable for long-term use. Finally, water demand is concentrated in a few densely populated areas, which do not necessarily coincide with the sites of greatest availability.

In brief, good-quality fresh water available in sufficient volumes and in a sustainable manner to meet the needs of populations and productive activities is not easily found. Increasingly, it has become a limiting factor in demographic and economic growth.

Water use and overuse

Water is the most widely used substance on Earth: it is needed in homes for washing, cooking, and drinking; it is used by industries as a raw material, for cooling or washing, to make possible certain processes; it is required for farming and for many other purposes. Farmers are responsible for more than 80% of the world’s water consumption. Of the remaining 20%, about half is consumed domestically and the rest is used by industries and for other activities.

These figures reflect only the water that is actually used, however. Additional large volumes of natural water are only “affected” by human action. Good-quality river or lake water is often rendered unfit for use by the return of untreated or insufficiently treated wastewater into its environment. The volume of natural water that is affected by human activities is enormous and difficult to quantify. In all likelihood, the volume of degraded water is probably on at least the same order of magnitude as all the water used worldwide, and may be substantially greater.

Another anthropogenic cause of water degradation or, at least, decreased availability relates to inappropriate soil management on slopes. Inadequate farming or grazing practices cause soil erosion, and runoff water carries agricultural fertilizers and pesticides. In such “overused” areas, water flow is often concentrated over a short period, causing flooding and making optimum use of the water resource more difficult. Floodwater is usually loaded with suspended particles that not only lower its quality but also clog intake mechanisms at filtration plants, making its treatment more costly and difficult.

Anthropogenic impact on water systems

In ancient times, hydrographic basins evolved naturally at variable paces depending on climatic, geologic, and biologic factors. Since the beginning of history, however, societies have introduced other factors. Agriculture, raising cattle, logging, excavation of quarries, and construction of artificial structures have had an effect on hydrodynamics throughout the planet. The growth of the world’s population, particularly after the industrial revolution, has gradually increased the impact of these factors as widespread modifications were made to the land surface. Anthropogenic effects have been particularly intense since the urban revolution of the 20th century. Overpopulation in many rural areas and the development of large cities with populations in the millions have created a concentrated and growing demand for water.

During this century, the amount of water used for agricultural, domestic, industrial, and other purposes has continued to increase; dams have been built, wells drilled, and water taken from natural sources at an unprecedented rate. “Used water” of lower quality is being resumed to the environment, causing widespread degradation of streams, lakes, and aquifers.

Vulnerability of water resources

The vulnerability of water resources to contamination varies from place to place. Generally, it depends on volume. Large rivers are less vulnerable than smaller rivers. The same rationale applies to lakes, although they are more susceptible than rivers because of their slower rate of renewal. However, surface water sources are relatively easy to clean up once a commitment is made to do so.

Groundwater, on the other hand, is less vulnerable than surface water in the short term. It takes longer for contaminants to find their way into deep aquifers. In some cases, they may even be protected by impermeable layers of soil or rock. However, groundwater reservoirs can be polluted easily by contamination of their recharge areas or inappropriate drilling operations. When this happens, the damage may be difficult and expensive to correct. In most cases, contaminated aquifers cannot be used for a long time and, in some cases, they may never again be suitable for any practical purpose.

Water problems in densely populated areas

The industrial revolution resulted in gradual growth of urban centres, with the populations of London, New York, and Paris exceeding I million by the beginning of the 20th century. Today, as
many as 200 cities have populations over I million and more than 20 have over 10 million people.

In most cases, water resources were abundant when these cities were first established. Many drew the water supplies from nearby rivers or lakes, which were more than sufficient. Where surface fresh water was not available, cities used easily accessible underground aquifers. In fact, in almost all cases, it was the presence of water resources that made the development of the new cities possible.

In cases of both spontaneous and planned development, however, almost without exception, the location of cities was not chosen based on anticipation of the growth that has taken place in many of the largest urban areas of the world. In the 18th and 19th centuries, most of today’s largest cities would now be considered small or medium sized. By 1800, no city in the Americas had a population over 100 thousand.

For these levels of population, only relatively limited water resources were necessary. In the early 19th century, however, even small cities had poorly developed water-supply systems. For this reason, per-capita consumption levels were much lower than they are today.

During the late 19th and 20th centuries, many cities grew to become megalopolises. At the same time, their need for water increased dramatically: in some cases, per-capita consumption increased to 600 litres per year. Large cities consume large volumes of water. Los Angeles, Mexico City, and Tokyo - three of the world’s largest cities - use 50 to 150 cubic metres of water every second. These volumes may seem impressive; however, they are relatively minor compared with the flow of our planet’s largest rivers. The efflux of the Amazon into the Atlantic Ocean is about 150 thousand cubic metres per second, 2 thousand times the consumption rate of the largest megacity of the world. The Congo flows at an average rate of 60 thousand cubic metres per second, and many other rivers, such as the Parana, Yangtze, and Mississippi, deliver over 5 thousand cubic metres of water to the sea or coastal estuaries every second.

This apparent overabundance of water does not reflect reality, however. The Amazon and the Congo are not typical because a significant portion of their basins lies in high rainfall areas. Many other rivers with large basins (such as the Nile and the Niger) have considerably lower flow volumes. On average, much less water is actually available. The numbers given here reflect the flow at the mouth of these rivers, where it is greatest. In other stretches of the rivers and in their tributaries, the flow is much lower in relation to the size of the upstream basin and local rainfall. Also, not many large cities or densely populated areas are located at the mouth or in the lower reaches of the largest rivers or their tributaries where water flow is at its maximum. As a result, the actual surface water resources available for cities and densely populated areas are much smaller than they would be if the cities were ideally located.

Many cities that are at the mouths of large rivers (such as Georgetown in Guyana and Montevideo in Uruguay) cannot use the water directly because of its brackish quality, which is caused by invading seawater during the dry season. Some cities are close to divides, so available water is limited (Sao Paulo and Madrid), or next to relatively small streams (Los Angeles and Lima). Available resources frequently cannot meet the growing needs of neighbouring metropolitan areas.

Despite potential problems, at the beginning of the 20th century, the world’s main urban centres were managing to survive using their nearby water resources without major problems of scarcity. During the 20th century, however, the situation changed radically. Cities that formerly had populations of 50 to 100 thousand have grown to urban areas of 10 to 15 million, housing as many or more people in surrounding areas. At current rates of growth, or even with some stabilization in the near future, by the beginning of the next decade there will be several megalopolises with over 15 million people.

In many of these megacities, local water resources have been exhausted or were degraded many decades ago, and water authorities have been forced to turn to neighbouring hydrographic basins or aquifers. As a result, the cost of water has risen considerably, although in most cases it is somewhat disguised in national budgets. Often, urban water-supply accounts list only operational costs, investments are financed at the national level, and, in some cases, even replacement costs are not fully considered.

When cities do not pay the full price of their water, however, someone else does. In many countries, large cities are being subsidized by the population at large, including taxpayers in small towns and rural people who do not benefit from the waterworks.

Continuing growth of large urban areas will make the problem more acute. New sources of water can only be farther away or deeper; tapping them will require more costly dams, conduction systems, storage structures, distribution networks, and treatment plants. A successful strategy will have to be aimed at redefining management strategies not only to increase supply, but also to reduce demand, unnecessary consumption, and losses. A longer term solution will require reexamination of the “constant growth” development paradigms that are the cause of unsustainability in current systems. A new approach may be required in which water consumption will be related to its distribution and availability and where rational and equitable demand policies are given priority over additional spending and waste.

Power generation

Water overuse is often related to the need to generate power. In Armenia, historical Lake Sevan is gradually being drained by the Razdan River power plants to produce badly needed electricity. The power plants were built in the 1940s and the water levels at that time were 20 metres higher that they are today. The lake is now eutrophic and its area is rapidly decreasing. In addition, because of the recent conflict between Armenia and Azerbaijan, Armenia was cut off from its oil supplies (which used to come from Azerbaijan) and electricity production in the Razdan plants has increased, accelerating the process of degradation (Gray 1993). This is yet another demonstration of how wars and conflicts between nations can destroy the environment.

Use of groundwater

In many areas, the volume of groundwater resources may be much greater than that of surface water; in terms of usable fresh water, the difference may be several orders of magnitude. However, the amount of groundwater available should not be measured by its volume, but in terms of its rate of renewal. When groundwater resources are used faster than they are replaced, water levels in aquifers drop, pumping costs increase, and sooner or later the resource is depleted.

Judging aquifers in terms of their renewability, available volumes of water are about equal to or less than those of surface resources. In addition, groundwater availability and urban populations do not necessarily coincide. Some large aquifers are located in sparsely populated areas or where they are not needed because sufficient surface water exists; at the same time, many large urban areas have very little groundwater in close proximity. Despite these limitations, the use of groundwater offers many advantages

· It is less vulnerable to contamination;

· It usually does not require treatment to make is suitable for drinking;

· It can be exploited using a modular approach with smaller capital investment and local participation;

· It does not require large, sophisticated distribution systems; and

· It does not need expensive storage structures - it is already stored underground.

Although groundwater may be a feasible alternative for providing water to urban areas, particular care must be taken to protect it from degradation by outside sources and from overuse. As mentioned above, although aquifers are less vulnerable to contamination, when they are affected, the damage may be irreversible.

The particular problems of coastal cities

A common limitation to water supplies in coastal areas is the intrusion of brackish water into the lower reaches of rivers. This has forced cities such as London (on the Thames) and Guayaquil (on the Guayas) to relocate their water-supply intake farther upstream.

Coastal cities depending on nearby aquifers for water have also experienced problems with saltwater intrusion as a result of drawing too much water from the underground resource. Seawater enters the aquifer when the piezometric level drops below a certain point.

Many of these cities - such as Recife, Brazil; Calcutta, India; Dakar, Senegal; Georgetown, Guyana; and Maracaibo, Venezuela - have had to pipe water from distant rivers or groundwater sources. Others, on salty rivers or estuaries, have turned to nearby freshwater tributaries. New York, for example, was forced to use groundwater because the Hudson River is brackish. Currently, its water supply comes from upstream reservoirs. Montevideo, Uruguay, cannot depend on the Rio de la Plata, which has an average salinity of 10%0 (per thousand), but gets its water from intakes in the Santa Lucia River, a tributary of the Rio de la Plata, 30 kilometres upstream of its mouth and 15 to 30 kilometres from the city.

Some coastal cities are not close to a river, especially those located on karstic or volcanic sites (for example, Djakarta, Indonesia; Manila, Philippines: Miami. United States: Havana. Cuba: and Merida, Mexico). These cities rely entirely on groundwater for their water supplies.

Other limitations

The growing contamination of surface water - resulting from a lack of wastewater treatment - is gradually becoming a central issue. In many densely populated areas, all types of wastewater find their way into the natural water systems. For example, there is a $3 billion plan to clean up the Tiete River in Sao Paulo. However, it is unlikely to be carried out before the year 2000 and there are indications from international and local environmental NGOs that, because of special interests and constraints, the project may never even approach its final goal.

In summary, there are two basic limitations affecting the water supplies of cities and densely populated areas of the world. One is the inappropriate location of cities in relation to existing natural water resources; the other is the growing degradation of those resources.

The demand side of the issue

Water-supply problems are not alone, however. In fact, the water problem has two sides: the availability of resources - or the supply side - and water-consumption issues - or the demand side. Many water-supply problems would not exist, or would be much less acute, if more sustainable policies and strategies were formulated and implemented that better accounted for the demand side.

In most countries and cities, consumption is actually much greater than what is required to serve human activities. Wastage takes place at all stages in water systems: leakage from pipelines, wasteful attitudes encouraged by a lack of metering or inadequate pricing policies, inappropriate water-appliance technology, etc. To improve the situation, this waste must be reduced through improved management strategies.

In most urban areas, water shortages could be prevented for many years with better system maintenance and appropriate metering and pricing policies. Such a strategy would be more economical in terms of both time and money and would reduce the deleterious effects on natural water systems. However, very few cities in the world have moved toward such a sustainable approach to water management. This lack of action is related to the types of development models that have been adopted in most countries.

Sustainability and equity in urban areas

To solve urban water-supply problems, management strategies must weigh required investments against returns within a framework of sustainability and equity. For every densely populated area of the world, there are several possible sustainable and equitable water-supply options. Usually, once sustainability and equity are assured, the main criteria for choosing among the various alternatives would be the financial costs of the proposed systems.

Many other factors enter the equation, however. Some relate to the concept of sustainability. First, water-supply systems should not affect the sustainability of the water resources themselves (that is, the rate of use should not be higher than the rate of renewal, and the quality should not be lowered). Second, the sustainability concept includes protecting other natural resources in the region (fluvial or lacustrine ecosystems should be protected).

In addition to ecological sustainability, water systems must be socially sustainable. The implementation of any water system involves socioeconomic implications, not only from the perspective of satisfying the needs of all the population in an equitable way, but also from other points of view. Establishing water services creates employment, promotes some types of industries, and even affects other urban strategies (for example, the availability of water will stimulate the development of some neighbourhoods over others).

Water and models for development in urban areas

Even with sustainable approaches to water management, population growth in many areas exceeds the potential of local, natural systems. In those cases, the problem does not lie in the resources, but in the development models that have flourished throughout the world during the last few decades and, in fact, the last few centuries. It is clear that megacities are not sustainable entities. One wonders, for example, about the future of Mexico City, with 20 million people and still growing. Water is becoming insufficient and huge amounts of money and energy are being spent to produce larger and larger volumes of water, but the city and surrounding urban centres (Toluca, Puebla, Cuernavaca, and Cuautla) are still growing. The development model of Mexico City must be reviewed, growth should be curtailed, and the country’s economy and management system must be decentralized. If these things are done in an intelligent manner, there is a real possibility that the water problem will disappear, or at least be significantly reduced.

In the Philippines and Thailand, the increasing centralization of the economies in two megacities is not sustainable. Neither Manila nor Bangkok is located in an area that can accommodate an urban population exceeding 10 million without irreversible deterioration of the environment, including the water supplies. The problem is also apparent in Brazil. Hydrologically, Sao Paulo was in the wrong place to start with, and time and further growth of the city have worsened the situation. A new model requiring the relocation of some of the city’s activities may be the only long-term solution to many of its serious problems, including its water supply. The same arguments could be applied to many other cities of the world; Tehran, Bombay, Dakar, Kinshasa, Lagos, and Lima, to various degrees, present similar problems.

Irrigated agriculture: one of the largest water users

In most countries, it is not urban populations that require the largest volumes of water, but irrigation. Irrigated farming uses an enormous amount of water, especially because areas that require watering to grow crops are normally located where evaporation rates are high, and this is exacerbated by the type of crops planted, some of which have high transpiration rates.

On 1 hectare of irrigated rice, for example, as much as 20 thousand cubic metres of water may evaporate every year. Even for less-demanding crops, irrigated farms use as much water for each hectare, on average, as 40 urban homes. For this reason, irrigated agriculture can be competitive only if crops of high market value are grown or where the price of water is very low.

Frequently, the low price of water for irrigation does not reflect actual costs. In some irrigated zones, water is obtained from systems in which the cost of expensive dams or other waterworks has not been factored into its price. The artificially low cost of water allows the development or persistence of irrigated farming in areas where it would otherwise be economically unfeasible. In those cases, farming only survives because it is being subsidized by the institution or agency that built or financed the waterworks and is not passing along the cost to the water users.

In many cases, the capital investment was financed by a loan to a national government and is being repaid by society at large. In California, for example, large hydroworks on the Colorado River and elsewhere were financed by the federal government. In Mexico, as well, the investment needs of most irrigation districts, as well as a considerable part of the pumping costs, are or were supported by the federal government.

Defining water strategies

One of the pressing problems facing those developing strategies for the future relates to the allocation of water to the often competing areas of irrigated farming and urban use. Farmers use far more water than urban dwellers (even when large water-consuming industries are considered).

For this reason, the competitiveness of agricultural activities is closely related to the cost of water. Expensive water can exclude the farmer from the market. Urban dwellers can afford to pay more per unit of water because the cost of aquiring the water is shared by many more individuals and enterprises and because they use much less water on a per-capita basis.

In the competition between farmers and cities, the cities tend to have the upper hand. In some cases, this may be to the detriment of traditional farming activities by many small farmers who depend on irrigation (such as in Egypt). In other cases, speculative water policies result in water being taken from small farmers or indigenous communities and provided to large companies for commercial production (for example, the water transfer from Owens Valley to the lower valleys in California).

For this reason, it is necessary when defining water strategies to take into account all the elements of the equation.

· How much water is available?

· Who needs it the most?

· What share should be provided to each user?

· Who has priority?

· What makes the most sense economically?

Finally, these concerns must be answered within the framework of sound development models in which quality of life and sustainable use of resources are the main priorities. Use of water resources will be optimal and the water situation will be addressed satisfactorily only when sustainable social and environmental models are properly defined and adopted.

Water issues throughout the world

Water has always been a central element in the history of humankind and its use has frequently had profound social, economic, and political implications. Policies and decision-making in this field can have a great impact on the future of countries and societies. There are many examples in which conflicts over water have been a determining factor in the evolution of countries and societies. The following pages will cover some important or representative basins, illustrating some of the key water issues with environmental, social, and geopolitical implications.

The Amazon basin

The Amazon basin, covering 6.157 million square kilometres, is one of the largest river basins in the world. It is shared by seven countries about two-thirds of the basin (4 million square kilometres) is in Brazil, nearly I million square kilometres lies in Peru, 825 thousand square kilometres in Bolivia, and the rest in Venezuela, Ecuador, Colombia, and Guyana.

The region is characterized by a high annual rainfall - averaging over 2 thousand millimetres - falling during two rainy seasons separated by drier periods. The vegetation is mainly dense rain forest, including extensive wetlands (almost 600 thousand square kilometres). The Amazon region is also home to some of the world’s largest and most diverse ecosystems.

Because the basin is sparsely populated (25 million people, mainly living in the highlands and on the slopes of the Andes, with a density of only four people per square kilometre) and there is plenty of water available throughout, there have been few contentious issues related to the management of its resources. With the growing drive to build dams and the encroachment of mining operations, this situation is expected to change.

The population density of the rain forest itself is very small, as most settlements are situated along the rivers. The major cities of the basin are Manaus and Belem, with about 1.5 and 2 million people respectively; others include Iquitos in Peru and Santarem in Brazil. The river plays an important role in both transportation and fishing. Travel between communities of the basin has traditionally been by boat, although lately air travel has also become important. Land routes are few and, in the heart of the forest, almost nonexistent. Fishing has been one of the main subsistence activities of the population. Thus, contamination of the aquatic bioresources may represent not only a health hazard but also elimination of a source of food and income.

The region is also home to numerous indigenous micronations, which are well adapted to using the forest ecosystems. Although the destiny of these groups is closely linked with that of the water systems, decisions on basin management are usually made without any consideration of their point of view or interests. Land policies in Brazil have traditionally favoured the newly arrived occupant, who can prove possession by burning or logging the forest, rather than native groups who have lived on the land for many generations.

An important drive to occupy the region has been promoted by the building of dams, particularly by Brazil, which is the largest country in the area and has defined hydroelectric dam construction as a national strategy. There are plans to build dams at 43 sites on 13 rivers; they will have a generating capacity in excess of 70 thousand megawatts (Mougeot 1988). This “hydro-development” drive is to be concentrated in three river systems: the Xingu (32%), the Tocantins (20%), and the Madeira (15%). A number of dams have already been built, both on the Amazon and in neighbouring basins (such as the Parana) with similar characteristics. In some cases, disastrous environmental and social effects have been observed (such as in the Tucurui impoundment on the lower Tocantins).

As a result of deforestation, hydrological regimes are already changing throughout the basin. Droughts and floods, formerly unknown, are taking place along many tributaries, and water quality is being affected by the increasing amount of effluent wastewaters entering the rivers from cities and mining operations.

Contamination from mining is related to the establishment of gold mines. Gold is extracted from ore using mercury or cyanide solutions. (In Brazil, the mercury technique is more common.) Both procedures damage the environment. Cyanide is highly poisonous and mercury becomes concentrated as it moves through the trophic chains and may reach toxic levels in some aquatic organisms that are consumed by the local people. In Japan, mercury poisoning affected the villagers of Minamata Bay in the 1950s, killing 1382 people (Serril 1994). In the Amazon, mercury pollution is particularly serious in the upper basins of the Madeira, Tapajos, and Xingu rivers, and there are indications that widespread poisoning may be taking place in some of the most polluted areas. In the fishing community of Rainha, upstream of Itaituba on the Tapajos, tests on the population showed mercury levels far in excess of the 6 ppm maximum accepted by the World Health Organization. Similar data were obtained in several other locations. In the Madeira River basin, hazardous levels were found in the fish-eating Kayapo communities. Continuing mining operations are expected to increase the environmental and human health effects of mercury contamination further.

With deforestation and indiscriminate occupation, the apparently invulnerable Amazon ecosystem is deteriorating, and this is not only affecting its inhabitants but also the population of the world at large. It will not be easy to address the many issues that are producing these changes in the Amazon basin. New policies will be required in many areas. Land allocation rules and recognition of the land rights of indigenous peoples should be reviewed. Migration to the region must also be checked through adequate policies. The environmental and social impact of hydro projects should be strictly and independently evaluated to ensure that no further ecological destruction takes place. Finally, any strategy will have to take into account not only the interests of the distant industrial metropolises but also the views of the people who live in and suffer most from pollution of the Amazon: the indigenous nations who have managed their land in a sustainable way for innumerable generations.

The Rhine basin

In many ways, the Rhine basin is quite different from the Amazon. Its population density is more than 120 times larger. In a relatively small area, it accommodates more than 50 million people and drains a basin located in seven countries Austria, Belgium, France, Germany, Luxembourg, the Netherlands, and Switzerland. Second, the river is much smaller. It is only 1 320 kilometres long, and it drains a basin of barely 185 thousand square kilometres. As the river flows from the Alps to the North Sea, it crosses Switzerland, France, Germany, and the Netherlands. In this medium-sized basin, there are scores of large cities and some of the most densely populated areas on Earth (such as in Belgium and the Netherlands).

Not only does this river basin have a high population density, but it is also located in one of the most heavily industrialized regions of the world. Most of Germany’s output, that of the Netherlands and Switzerland, and an important part of France’s (Alsace and Lorraine) is produced or finds its way through the Rhine basin or its tributaries.

The intensive use of the basin has caused heavy contamination of the river, particularly in its lower reaches in Germany and the Netherlands. In 1985, pollutants in the Rhine at the border of the Netherlands and Germany were measured at the following levels chloride, 1.1 million tonnes per year; phosphate, 3 500 tonnes per year; copper, 450 tonnes per year; cadmium, 10 tonnes per year; and benzpyrene, 1 600 kilograms per year (Maurits la Riviere 1989). The situation grew worse until 1980, but has improved more recently. Currently, the four countries bordering the river are cooperating under the Rhine Action Plan to address the problems of water quality in the river. One of the main strategies to be implemented includes improving industrial processes to reduce the number of contaminants entering the environment.

In addition, there has been a trend toward relocating some of the highly polluting industries to developing countries that have less-stringent environmental controls and cheaper labour (see Chapter 2).

The Nile basin

The Nile basin presents potential management problems that could become litigious issues between countries. The sources of the White Nile and its tributaries are in the African great lakes region, mainly in Uganda, but also in Kenya, Rwanda, and Tanzania. The Blue Nile and the Atbara, which are the main eastern tributaries, flow down from the Ethiopian highlands and provide not only a substantial portion of the water volume but also most of the sediment load. The middle course of the Nile, below the confluence of the White and the Blue tributaries, is in Sudan, and its lower course is in Egypt.

Because the river flows from humid areas (in the south) to increasingly dry areas (in the north), the downstream populations of northern Sudan and Egypt have depended on its water for centuries. In Egypt, where rainfall does not exceed 100 millimetres annually, the Nile is the only source of water. Egypt has a population of almost 60 million, concentrated chiefly along the banks of the Nile; most Egyptian towns and farms are densely packed in the 40 thousand square kilometres of the Nile’s floodplain.

Any change in the Nile’s regime could be a matter of life and death for the Egyptians. Currently, an international treaty ensures a minimum flow for Egypt at its southern border with Sudan. Sudan does not use its whole share of water; therefore, problems have not arisen yet.

A potential problem relates to the use of groundwater near the river. In northern Sudan and southern Egypt, the river crosses the Tertiary sedimentary basin of Nubian sandstone, which contains a large and relatively unstudied aquifer. An important portion of the water recharging this aquifer comes through infiltration from the Nile. Any large-scale use of the aquifer may result in a reduction in flow downstream. It will be difficult to control Sudan’s use of the aquifer, as the relation between groundwater and surface water use has not been firmly established. Recent problems in multiethnic Sudan have prevented its inhabitants from increasing their use of water for irrigation.

Another potential problem for Nile communities is the proposed draining of the Sudd wetlands with the construction of a 360-kilometre canal (the Jonglei Canal) and other related waterworks. The Sudd region of southern Sudan is an area of high biodiversity that not only regulates the flow of the White Nile, reducing the risk of catastrophic floods and droughts, but also provides abundant resources to the Nuer, Dinka, and other peoples who have lived in the area for many generations. The continuing state of war in southern Sudan has forced the project to be abandoned, and it is unlikely to be completed in the near future.

Similar problems may arise in Ethiopia, where the Blue Nile and the Atbara rivers arise, providing 85% of Egypt’s water. Egyptians are concerned about the possible future construction of dams for power supply or irrigation in the upper basins. Political instability in Ethiopia has made any large-scale hydro development impossible, but this situation may change in the future. There have been talks regarding the construction of a dam on Lake Tana, the source of the Blue Nile, and this may affect Egyptian control of Nile waters (Pearce 1991, p. 36).

A more real and pressing problem in the Ethiopian highlands is the widespread destruction of the forest or shrubby ecosystems in the upper basins. River regimes have become much more extreme, with extended droughts punctuated by periods of increased runoff. Intense erosion of the basin soils has caused a considerable increase in the solids content of the water and silting effects downstream. The Aswan Dam has been particularly affected by increased silting, which has reduced the length of its usefulness to merely a few decades.

The Aswan Dam in upper Egypt was completed in 1970; its inauguration allowed the opening for agriculture of extensive formerly arid lands. Apart from its initial positive impact on agricultural production, however, the dam has had a number of negative effects. One relates to conditions necessary for agriculture on the floodplain downstream from the dam. Because the dam has reduced the amount of silt reaching the plain, artificial fertilizers are required, increasing costs and affecting the water quality of the river. The newly irrigated soils have also been waterlogged, and salinization of soils and groundwater has become a common problem. Human health was affected by an increase in schistosomiasis. Construction industries suffered because they depended on a supply of alluvial silt to make bricks. Brick-makers often compete successfully with farmers for the same land. As a result, traditional farming areas have been reduced along with agricultural production.

The Nile basin is a fragile hydrographic system requiring careful management. Much coordination will be necessary to ensure that it is used appropriately and sustainably. However, management of such a complex and multinational basin is not merely a scientific endeavour. It encompasses political, social, economic, and historic issues. Only a holistic approach will permit resolution of its long-term problems without conflict and allow its optimum use to improve the quality of life of its population.

The Jordan River basin

Although the Jordan is a small river, it is located in an area where water resources are extremely scarce because of low precipitation (ranging from less than 100 millimetres in the south to about 500 millimetres in the northern highlands) and a history of acute political conflict between the countries sharing its basin (Lonergan and Brooks 1994).

There are five countries in the basin: Israel, Jordan, Lebanon, Palestine, and Syria. The upper basin is mainly in Lebanon and Syria, where the Hasbani and Banias rivers, together with other neighbouring springs in Israel, feed Lake Kinneret (the Sea of Galilee), which has a volume of 4 billion cubic metres. The main outlet from this lake is the Jordan River, whose waters are shared by Israel, Jordan, and the Palestinian West Bank. The total annual flow in the river brings 611 million cubic metres of water into the Dead Sea, whose salinity is 250 thousand ppm, or seven times that of seawater. To further complicate the political aspect, a considerable portion of the water flows underground (some toward the river valley and lakes and some toward the Mediterranean), increasing the chances for conflicts.

In an international basin such as this one, environmental management must be based on water-management policies and strategies. Every human activity depends in one way or another on the decisions that are made regarding water. Solving water issues in this part of the world will probably be the first step toward a lasting peace.

The Aral basin

For a long time, the Aral Sea in central Asia was the fourth largest lake in the world, with a unique ecosystem that had evolved in isolation for many millions of years and contained a diverse flora and fauna in its 50 thousand square kilometres.

During the early 1960s, the Soviet government implemented a mammoth irrigation project to grow cotton using water from the Syr-Darya and Amudar’ya rivers. The project affected, directly or indirectly, the republics of Kazakhstan, Kirghizia, Turkmenistan, and Tajikistan. Unfortunately for the surrounding communities, the volume of the lake depended almost exclusively on water from these two rivers. Their flow was substantially reduced as water was diverted to cotton plantations. The amount resuming to the rivers and the lake was, and still is, only a fraction of the previous volume and was heavily loaded with agrochemicals. After three decades, the Aral Sea is dying. Its ports are more than 80 kilometres from the lakeshore, its marshes and forests have perished, and the aquatic ecosystems have shrunk and lost much of their biodiversity (Pearce 1994a). The volume of water in the sea is only 40% of what is was only 33 years ago. Its volume continues to decrease by 27 cubic kilometres every year, the surrounding aquifers are drying up, and, in about 20 years, the sea is expected to disappear completely (Pearce 1994b).

The unsustainability of the model is clear. The cotton fields are waterlogged and the soil is becoming salty. There are almost no fish left in the lake. In some communities (such as Nukus), the water is unfit for drinking. Despite general agreement of the part of the various interested states that the situation must be improved, no targets or timetables have been set for doing so. In light of the current economic situation in the basin countries, it is doubtful that corrective measures will be implemented in the near future.

The Chad basin

The Chad basin is an endoreic hydrographic system extending over about 2.7 million square kilometres in the western part of central Africa. The northern portion of the basin lies in the semi-arid and arid regions of the Sahel and Sahara. The southern and eastern sections are mainly in the savannas of Sudan, Cameroon, and central Africa, although it occupies forested areas in the south. The basin is shared by several countries, of which the largest is Chad. It depends on the basin for most of its agricultural production and fisheries. The centre of the basin is occupied by a water-filled depression whose area varies with rainfall - Lake Chad.

The main rivers of the basin are the Chari and Logone, flowing from the highlands of Cameroon and the Central African Republic. These systems are, by far, the greatest suppliers of water to Lake Chad - 28 billion and 12 billion cubic metres per year respectively. These rivers flood their alluvial plains (the Yaeres) and the shores of the lake annually. The actual flooded area is estimated to be about 59 million hectares. The variations in the hydrological regime of the Logone River are important; at Baibo-Koum, a maximum flow of 4 438 cubic metres per second and a minimum flow of 13 cubic metres per second have been observed.

The Yaeres are the “breadbasket” of the Chadian region. Rice is cultivated using the floodwaters, and millet is planted in drier areas or after the floodwaters recede. Animal production is carried out in association with farming activities using itinerant strategies. Over 100 thousand animals are brought to the Yaeres annually to graze. Chadians also harvest an average of 80 thousand tonnes of fish annually from the basin.

In the 1960s, a large development project with international funding was proposed for the widespread irrigation of the Chad lowlands: the South Chad Irrigation Project. The project was to use the water to “green the surrounding deserts.” Planning began in 1962, at the end of a period of unusually high rainfall. According to one designer, the project was a disaster. The hydrologic study was carried out over only 3 weeks, the idea of securing a different source of water “was dismissed out of hand,” and it was assumed that the project was designed to operate for all water levels in the lake. In 1992, the intake areas were dry and many rotting ships were littering the landscape, often more than 60 kilometres from the lakeshore. As well, 4 thousand kilometres of canals were permanently dry and some villages that were flooded in 1962 were almost 100 kilometres from the shoreline.

This situation is not expected to improve over the medium or even long term. The lake loses 2 metres of water through evaporation every year and the flows of the Logone and Chari rivers have been cut in half. However, it is important to remember that in this case - as in many others - the problem does not lie in the natural variations of rainfall or in the high level of evaporation; rather, it lies in the manner in which the project was conceived, designed, and implemented and in the unnatural and nonparticipatory view of “development” that inspired the project from its inception.

The Colorado River basin

The Colorado River (Figure 2) rises in the Rocky Mountains and flows down the west face of Longs Peak, almost 4 thousand metres, as it begins its 2 400-kilometre journey to the Pacific Ocean. It receives runoff from the western areas of the Colorado, forming the Grand Valley where the first large irrigation developments are located. When the river enters this valley, its salinity is only 200 ppm; as it leaves the area after irrigating its crops, the salinity averages as much as 6 500 ppm.

Farther downstream, the river is joined by the Gunnison and the Green tributaries before forming the Powell reservoir behind the Glen Canyon Dam. Several new tributaries join the Colorado below this dam (Little Colorado and Virgin), increasing the flow, which is again dammed farther downstream forming several artificial lakes: Lake Mead above the Hoover Dam, Lake Mojave at the Davis Dam, and Lake Havasu at the Parker Dam.

The river then receives the brackish water of the Gila River, which increases its salinity slightly until it reaches one of the largest interbasin water-transfer operations in the world, the aqueduct to California, where one-third of its flow is pumped westward. The water is channeled into the Imperial Valley, Los Angeles, and San Diego to satisfy the needs of thousands of Californian farmers and millions of urban dwellers. Many of the fresh winter vegetables in the United States are produced using Colorado waters, and at least half of the water consumed in greater Los Angeles, San Diego, and Phoenix comes from the Colorado.

Only a small proportion of poor-quality water is left in the river when it finally crosses the Mexican border. To solve critical binational problems, a treaty was signed with Mexico in the 1970s to ensure better-quality water in the lower reaches of the river. Recently, the US Congress approved investments in equipment for salt removal at a Yuma plant. It will cost $300 per unit to desalinate water that irrigators buy for $3.5 per unit upstream.

Figure 2. Dams and reservoirs of the Colorado River.

As will be described in Chapter 12, the Colorado River has been changed considerably, and not necessarily for good reasons. Today, the river is largely an artificial system; aquatic life has been affected both in the river and in the Gulf of California; its flow has been curtailed; and its aquifers have been directly or indirectly modified, reducing the sustainability of the systems. The model of the Colorado River is another example of inadequate and nonparticipatory use of natural resources. We can only hope that the 21st century will see some of the worst effects of these pharaonic, 20th century hydroworks undone.

The aquifers of the western United States

Similar problems of widespread and thoughtless interference with nature can be observed in the aquifers and basins of central California. At the beginning of the century, almost all of California’s water came from groundwater sources; now the proportion is 40%. The farmers of the central valley (Sacramento and San Joaquin valleys) overused the water and, by the 1930s, the farming economy was approaching collapse. The farmers convinced the legislature to authorize the Central Valley Project, by far the largest water project in the world; it was partially financed by the Roosevelt government. In the 1960s, the California Water Project, of similar size, was implemented. Together, these projects provide eight times the amount of water needed for the city of New York.

Despite the additional water, however, overuse continued because, instead of merely substituting the new sources for the older, over-exploited sources, farmers opened up more land for cultivation. Estimates of the amount used over the renewal capacity of the aquifers in California range as high as 3 billion cubic metres per year, causing a growing water crisis throughout the state.

The lack of regulation pertaining to groundwater pumping, a traditional “absent” feature of the California legal system, has probably been a major factor contributing to the current critical situation (see box 6). However, cases of overexploitation of groundwater resources are not restricted to California or the United States. They can be found worldwide from the valley of Mexico to Bangkok, and from Manila to Havana.

6. The Ogallala aquifer

The Ogallala aquifer is one of the largest and most heavily used groundwater reservoirs on Earth. Most of the water for irrigated farming in Texas, Kansas, Colorado, Oklahoma, New Mexico, and Nebraska comes from this huge underground basin. Continued overextraction has gradually reduced pressure in the aquifer - wells are no longer artesian, water levels have dropped, and pumping costs have increased. Lately, awareness of a vanishing resource has raised questions about the need to respect limits of renewability to protect the water resource.

Traditionally, sustainability of groundwater was not a concern in the US midwest. An example of the philosophy inspiring groundwater policy and decision-making in the field of resource management during the 1950s and 1960s (and today in some cases) is supplied by Felix Sparks, former head of the Colorado Water Conservation Board. When asked about the future of groundwater in the state, he responded with a rhetorical question: “What are you going to do with all that water? Leave it in the ground?” The state engineer in charge of water in New Mexico (Stephen Reynolds) further illustrated this line of thought: “We made a conscious decision to mine out our share of the Ogallala in a period of 25 to 40 years” (see Reisner 1986).

According to this approach, the solution to water scarcity was more water projects, including some that were very expensive and resulted in returns as low as 5% in economic benefits.

In Reno, Nevada, gambling and prostitution are legal, but for a long time water-metering was against the law.