The dams will be in your interest. They will bring progress. With these words, the Chief Engineer for Brazil's electricity conglomerate, Eletronorte, concluded his case for building a series of massive hydroelectric dams on the Xingu river. His audience, however, was unimpressed. It consisted of about a thousand Amazon Indians, who had assembled at Altamira, a boom-town in northeastern Amazonia, in the first-ever mass gathering of Brazil's tribal peoples against a dam project.
The Indians rose to their feet, raising their arrows and clubs in protest. A woman strode to the dais, streaked in warpaint, brandishing a machette and cutting the air to emphasise her points. She brought down the machette in a graceful but swift arc, stopping just a hair's breadth away from the engineer's shoulder blade.
"We don't need electricity. Electricity won't give us food. We need the rivers to flow freely. We need our forests to hunt in. We are not poor. We are the richest people in Brazil. We are not wretched. We are Indians."
On this occasion, the protests proved successful. Under pressure from environmental groups, the World Bank announced that it would withdraw funding from the project. The Brazilian government reluctantly agreed to shelve the scheme. But the Indians know that the threat is still there. And that their river may well go the same way as hundreds of others across the globe – dammed and polluted in the name of progress.
Every year, over 400,000 cu. km. of water evaporates from the oceans into the atmosphere. 90% of that water returns to the ocean as rain, sleet or snow, but the rest falls over land. As the snow melts and the rain runs off the land, it collects in streams and rivers, cascading down mountains and into the plains on its long journey back to the sea. The cycle begins again, ensuring that life on the land can survive. For without water, even the hardiest desert plants would wither, animals would die of thirst and the earth would be a moonscape.
When the ancient Greek philosopher Heraclitus said that one could never put one's feet in the same river twice, he captured the forever changing, yet seemingly unchanging, nature of rivers. Their waters are always on the move – sometimes violently so, sometimes at a snail's pace – rising and falling with the seasons. In the spring, when melting snow in the mountains swell a river's waters, the sheer force of the flow can uproot plants and snap reeds. The river's banks may burst, spilling water onto the surrounding land. To survive, the plants and animals that live in rivers or on their banks must be able to cope with such change. Many plants, for example, have developed the ability to root again when snapped.
the sheer physical force of the water as it cascades
over rocks and shingle leaves little sediment on the riverbed. Picture: Kunal Verma
As rivers tumble down the mountains and hills where they rise, their waters flow faster than in the low-lying plains below. The speed at which a river flows makes a critical difference to the wildlife that is found there – and the strategies they have evolved to survive. As rivers tumble down from the mountains where they rise, the sheer physical force of the water as it cascades over rocks and shingle leaves little sediment on the riverbed. Here, apart from such fish as salmon whose powerful muscles enable them to swim against the stream, only those plants and animals which can attach themselves to rocks survive. In the slower flowing reaches, the sediment carried down from the mountains provides a nutrient-rich bed in which plants can readily establish themselves. Fish are more numerous, as are the birds that prey on them, from iridescent kingfishers to ungainly pelicans.
Millions of people around the world depend on rivers for their livelihood. The fertile alluvial soils of floodplains, the rich fisheries and the ready access to water have encouraged settlements along river banks for millennia. Over a million people inhabit the Senegal river basin in West Africa, tens of millions in the Niger basin and hundreds of millions in the Ganges basin in India. The world's greatest cities have grown up along the banks of rivers – London, Paris, Rome, New York and Bangkok. But as humanity demanded more of its rivers, so their future is in increasing jeopardy.
In the arid southwest of the United States, where rainfall rarely exceeds twenty inches a year, local farmers have an expression: 'A wild river is a wasted river'. Their whole way of life depends on capturing the water in rivers, storing it and re-routing it to areas, often hundreds of miles away, which would otherwise have none. Without dams and canals, much of the land would still be scrub, useless for agriculture. Cities such as Phoenix, Arizona or Denver, Colorado, would cease to exist.
The southwest of the United States is by no means exceptional. Over half of the world's land surface is classified as 'arid' or 'semi-arid'. In some areas, rainfall is so sparse as to make rain-fed agriculture impossible. In others, farmers must survive for most of the year with little or no rainfall. And when the rains come, during the annual monsoon, they fall in such torrents that much of the water simply runs off and is lost to the sea. By damming rivers, water can be stored for use in the dry summer months and areas where rainfall is inadequate can be brought under irrigation.
Dams have the additional advantage of enabling humans to tap the vast energy potential of rivers. By chanelling the water in reservoirs through giant turbines, electricity is generated – and in vast quantities. The Itaipu dam in Brazil alone generates 12,000 MW – enough electricity to power New York. Dams already supply more than a fifth of the world's energy and if all the rivers of the world were to be dammed, they could produce as much electricity as 12,000 nuclear reactors. Small wonder that dams are seen as vital to economic development, supplying countries with the 'power to progress'.
and international aid agencies, the
Third World too has set out to 'tame'
its rivers. India, in particular, has invested billions of dollars in its dam-building programme, with over 1,500 dams built to date.
Picture: Debal Sen
The technology that has brought water to the arid southwest of the United States or to the drylands of Africa and India is not new. Nor is the use of water power to drive machinery. For centuries, man has built dams and water mills. Indeed, the embankments and water storage tanks that remain at such ancient capitals as Angkor Wat in Cambodia bear proud witness to the engineering skills of those who constructed them.
But advances in concrete technology and the development of vast earth-moving machines have enabled dams to be built and rivers to be manipulated on a scale that would have staggered the ancients. In California, for example, engineers have defied nature, redirecting whole river systems in order to bring water to the thirsty south. Massive 300,000 horsepower pumps siphon billions of cubic metres of water over the Tehachapi mountains to irrigate the farmland of the Imperial Valley, south of Los Angeles. All but three of California's large rivers have been dammed, many of them more than once.
The era of large dam building began in 1935 with the construction of the massive Hoover dam on the Colorado river in the United States. Rising over 700 feet from the bedrock of the river, the dam was at the time the largest single engineering structure ever built. Since then, river after river in the United States has been dammed, to the point where few still flow unimpeded to the sea. Some 50,000 major dams now straddle the rivers of the United States. Five dozen dams have been built on the Missouri river alone, 25 on the Tennessee. On such rivers, the transformation is so complete that hydrologists no longer refer to them as rivers but as 'regulated streams'.
With funding from the World Bank and international aid agencies, the Third World too has set out to 'tame' its rivers. India, in particular, has invested billions of dollars in its dam-building programme, with over 1,500 dams built to date. Along the Narmada river, which flows through the states of Maharashtra, Madhya Pradesh and Gujarat, work is underway on one of the biggest dam-building programmes in Asia. By the time it is finished, 30 large dams, 135 medium-sized dams and 3,000 minor dams will impound the river and its tributaries.
Few technologies have had a greater impact on rivers and their peoples than large dams. For those living in the river valley immediately behind the dam, that impact begins even before the floodgates are closed. They must move to make way for the dam's reservoir. Millions of people have now been uprooted. Still more will have to move in the future, the Narmada complex alone threatening to displace over a million. Whole cultures have been shattered and many of those resettled have ended up in slums. The building of the Kariba dam on the River Zambezi displaced 57,000 people, who had previously farmed the fertile floodplains on either side of the river. Although the government promised that they would be 'no worse off as a result of the dam', they were moved to land so marginal that for several years they depended on food aid for their survival.
In some cases, local people have resisted the move. A few have proved successful but most have found themselves facing governments unwilling to compromise. In 1989, as the floodwaters of the Kedung Ombo reservoir in Indonesia began to rise, some 1,300 families took to the roofs of their houses, then to rafts, hoping that the government would relent and stop the project. It would not and the reservoir kept on rising, drowning a whole way of life. At the height of controversy over the Jonglei canal in the Sudan, a regional governor told opponents, "If we have to drive our people to Paradise with sticks, we will do so for their good and the good of those who come after them."
As the reservoir of a dam fills, so the river ecosystem is changed forever. The rising floodwaters spell death for the many animals that live in the river valleys. Efforts to rescue wildlife before the reservoir begins to fill have proved a limited success. The numbers rescued are often small and many do not breed successfully after being moved. Moreover, little or nothing can be done to save the numerous species of insects and plants that live along the river.
Fish are also affected. In a reservoir itself, those species that depend on free-flowing water give way to species better adapted to a lake environment. Initially, the fish tend to thrive, encouraged by the release of nutrients from the submerged soils. Local fisheries have therefore benefited. But, all too often, it is a short-lived bonanza. As the submerged vegetation rots, it uses up the oxygen in the water, transforming the reservoir into a stinking and stagnant morass in which few fish can survive. Noxious weeds, such as water hyacinth, have also invaded reservoirs, blocking out sunlight and reducing fish populations. At many dams, weeds and rotting debris have clogged up the turbines used to generate electricity, rendering the dam inoperable.
For migratory fish, such as salmon and sturgeon, dams have proved particularly disastrous. In the south of the erstwhile Soviet Union, sturgeon catches fell drastically after dams cut the sturgeon off from their spawning grounds in the major rivers entering the Caspian sea.
The building of reservoirs has also led to an increase in waterborne disease. In contrast to the flowing waters of a river, the still shallows of a reservoir provide an ideal breeding ground for mosquitoes that carry malaria and the snails that carry bilharzia, a tropical disease which causes fever and anaemia. Following the building of the Aswan dam, the rate of schistosomiasis among the local population trebled. In some villages, everyone was affected.
The impact of dams does not stop with the dam itself. In those river valleys where farmers rely on the annual flood to irrigate their crops and to bring the nutrient-rich silt that fertilises their land, dams can have a disastrous impact. Held back by the dam, neither the flood nor its precious silt reaches the floodplains downstream, jeopardising the livelihoods of thousands of farmers. Downstream fisheries too are affected. Before the building of the Aswan dam, for example, the sardine fisheries along the eastern Mediterranean were plentiful. Deprived of the nutrients in the Nile's silt, however, catches plummeted by 97%. The reduced silt-load of the river also results in the riverbeds gradually being eroded, since the eroded sediment is no longer replaced by the deposition of new silt.
The trapping of silt behind dams is now leading to their premature closure. The silt reduces the capacity of reservoirs and hence their useful lives. The problem is particularly severe in the tropics, especially in areas which have been heavily deforested. In China, the Laoying dam silted up before it had produced a single megawatt of electricity.
For those cultures which practice seasonal irrigation, the annual flood is an occasion to be welcomed. But for those who have built their homes on land reclaimed from wetlands or who farm drained land, floods spell devastated villages, ruined harvests and misery.
Throughout the world, but particularly in the tropics, floods are on the increase, as is the damage done by them. Deforestation in the watersheds of rivers is a major cause of the increase in flooding. Without trees and vegetation to soak up the monsoon rains, the water cascades down into the valleys below. To prevent flooding – and to make navigation easier – riverbeds have been dredged, river courses straightened and rivers turned into little more than concrete waterways. Dams have also been built to store flood waters for slow release later in the year.
Picture: Anish Andheria
It is a strategy which has encouraged people to settle on floodplains in the belief that they will be safe from the ravages of even the wildest rivers. Inevitably, when floods occur, the damage is all the more extensive.
It is also a strategy which has wrought ecological havoc on river systems. As the bulldozers and diggers move in, so the habitat for river animals and plants is systematically destroyed. The meandering bends that slowed the flow of rivers, creating a habitat for bulrushes and other reeds disappear as the river is straightened and its waters are directed through lifeless concrete embankments. Trees and other vegetation along the banks are uprooted and the banks cut to the precise geometric shapes laid down by engineers more concerned with water flow rates than the survival of water voles or willows. Repeated dredging removes the weeds that feed fish and water insects such as dragonflies. Fish populations decline and with them, the birds that prey upon them, such as the kingfisher and the heron.
The tragic irony is that the 'channelisation' of rivers and streams has failed to prevent the problem of flooding and in many cases has exacerbated it. In India, nearly one billion dollars was spent on building embankments and canals between 1953 and 1979, yet the damage done by floods continues to increase year by year. Embankments prevent rivers from bursting their banks and so depositing their silt on the floodplains, with the result that the silt accumulates in the river, causing the riverbed to rise. The height of the embankments must therefore be raised and, in many areas, the level of rivers is now several feet above that of the surrounding land. When a breach occurs, as inevitably they do, the result is disaster. Dams too have a sorry record when it comes to flood control. The vast majority have been built to supply irrigation water or hydroelectricity. Unfortunately, those goals are at odds with flood control. In California, for example, heavy snowfall in the winter of 1983 resulted in greatly increased run-off from the Rocky Mountains during the following spring. The waters of the Colorado river swelled to almost unprecedented levels, quickly filling the reservoirs along the river. Rather than release the water, however, the water authorities insisted on keeping the reservoirs full, to squeeze every kilowatt from the river's hydroelectric stations and to maximise the storage of water for irrigation. Inevitably, the storage capacity of the reservoirs was soon exceeded, forcing the authorities either to release the water in one massive surge or face the possibility of the dams bursting under the strain. 50,000 acres of farmland downstream were flooded, thousands of people were made homeless and an estimated $100 million worth of property was destroyed.
The world, as we now know, is too small a place for one habitat to be ruined without affecting many others.
Edward Goldsmith is the Founding Editor of The Ecologist. Nicholas Hildyard is a former Editor and Peter Bunyard is currently Science Editor of The Ecologist. Patrick McCully is the founder of International Rivers Network. This is an excerpt from their seminal work, 5,000 Days to Save the Planet.