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Thirty years ago next week, Soviet engineers diverted the flow of the Nile, the world’s longest river, so that a huge dam could be completed across its bed. More than 17 times the volume of the Great Pyramid at El Giza, and still regarded as an engineering wonder of the world, the Aswan High Dam was to be, in the words of its instigator Colonel Gamal Abdel Nasser, ‘a source of everlasting prosperity’ for Egypt.

The dam stretches nearly 4 kilometres across the river’s path, and rises to over 100 metres from a base almost 1 kilometre wide. Behind it, the pent-up waters of the Nile have created Lake Nasser, the second largest artificial lake in the world. The reservoir, which winds upstream for 500 kilometres and widens to 60 kilometres in places, can store the equivalent of two years’ flow of the Nile.

Work on the project started in 1960 and continued for a decade, consuming about $1 billion in the process, or about 10 times that amount at today’s prices. Its purpose was to provide Egypt’s rapidly expanding population, which now stands at 55 million, with cheap power and a constant supply of water. This would allow farmers to irrigate their land even during the region’s persistent droughts. In 1964, the dam began to store water and, four years later, it delivered its first power to the national grid from giant turbines capable of generating more than 2000 megawatts of hydroelectricity.

The dam had a political purpose, too. It was a defiant gesture by Nasser to his foes in the West. At the impoundment of the dam in May 1964, Nasser declared: ‘Here are joined the political, social, national and military battles of the Egyptian people, welded together like the gigantic mass of rock that has blocked the course of the ancient Nile.’

The World Bank, the US government and Egypt’s former British advisers had refused to give his revolutionary government, which came to power in a coup in 1952, technical or financial aid for the dam. Nasser responded in 1956 by taking over the Suez Canal, then the most important waterway in the world, and announced that ‘the canal will pay for the dam’. Two years later, the Soviet Union stepped in with technical assistance, turning the project into a symbol of the Cold War and Russia’s growing influence in Africa.

Nasser also saw the Aswan High Dam as symbolising his country’s regional domination. Before building the dam he had to secure a deal with Sudan, its southern neighbour, part of which would be flooded by Lake Nasser. The Nile Agreement in 1959 gave Egypt two-thirds of the river’s annual average flow of 84 cubic kilometres; the rest went to Sudan. But Nasser left out of the deal the seven other Nile nations farther upstream: Ethiopia, Uganda, Zaire, Tanzania, Kenya, Rwanda and Burundi. (There is now an eighth, Eritrea.) He warned them that he would go to war with any that took Egypt’s water.

Of these upstream neighbours, the most aggrieved was Ethiopia, whose territory includes the headwaters of the Blue Nile and of the smaller Atbara and Sobat, which together make up 85 per cent of the main river’s flow. The White Nile, which rises in Burundi and converges with the Blue Nile at Khartoum, accounts for the remainder.

After the Soviet Union’s diplomatic coup at Aswan, the US retaliated by drawing up plans for four giant dams on the Blue Nile in Ethiopia. None got very far, however, because Ethiopia soon came under the control of the Marxist Haile Mariam Mengistu, who ruled with increasing tyranny and inefficiency until the end of the 1980s. This left Egypt with virtually uncontested control of the Nile’s flow through the Aswan High Dam.

Three decades on, however, the dam no longer assures Egypt of water, let alone power and prosperity. Evaporation from Lake Nasser is immense and, as a result, Egypt is starting to reconsider long-abandoned schemes to store water far from its own borders, in the highlands of other Nile nations. Furthermore, the dam has disrupted the flow of the river so much that it threatens the survival of the Nile delta, whose fields have been farmed for millennia.

Few dams excite as much controversy as Aswan. Unusually, environmentalists and cold warriors in the West have been united in condemning it. Even today, says the leading American geographer Gilbert White, ‘it is praised as the mainstay of the Egyptian economy and vilified as an environmental catastrophe’.

Popular problem

Mahmoud Abu Zeid, head of Egypt’s Water Research Centre in Cairo, believes the criticisms are unjust. As soon as it was completed, he complains, the dam became ‘the most popular environmental problem in the world – a global symbol of environmental and social problems caused by large-scale development projects’. In fact, he says, farm output increased by between 10 and 20 per cent within five years, and in the early 1970s the dam’s turbines provided half of Egypt’s electricity.

The controversy arises, in large part, because there are losers as well as winners in the changes wrought by the dam. And many fear that immediate economic gains will be overtaken by long-term environmental damage.

First, the benefits. Though the Aswan High Dam was not the first dam on the Nile, it was the first to capture the whole annual flood, allowing water to be controlled downstream at will. As a result, river flows could be kept higher through the long dry season and more of the Nile’s flood plain could be double-or even triple-cropped, often with water-hungry crops such as rice.

The dam also allowed water to be stored from one year to the next. This is especially valuable because low-flow years on the Nile come in clusters. There were seven such years in the 1980s, before heavy rains in the Ethiopian highlands led to a major flood in 1988 that replenished the reservoir. While people starved near the source of the Blue Nile in the mid-1980s, the Aswan dam collected what flow there was and protected Egyptian agriculture from collapse.

Tony Allan, a specialist on Middle East water at the School of Oriental and African Studies in London, sees this as possibly Egypt’s biggest gain from Aswan. Arguably, he says, ‘water security has been the major contribution of the High Dam to the Egyptian economy.’ But the project’s contribution to Egypt’s national grid has also been considerable, he notes. Though other power stations are now in place, and the Aswan dam meets only about 10 per cent of the country’s demand, Allan estimates that its hydroelectricity is still worth $500 million a year.

The clearest losers from the dam have been the 100 000 or more Nubians, half in Egypt and half in Sudan, who had to move from homes in the zone flooded by Lake Nasser to government-built villages far from the river. Less tangibly, there was the drowning or relocation of great archaeological monuments such as the temples at Abu Simbel, whose move out was largely financed by UNESCO.

After this, the arguments become less clear-cut. There are debates about the disappearance from the Mediterranean of the sardines that once bred in the Nile estuaries; about the build-up of algae in the river water; and about the spread of bilharzia, a debilitating disease harboured by snails that proliferate in the static waters of reservoirs and irrigation canals.

But the most serious criticisms, especially when it comes to the long-term consequences of the dam, concern silt and salt. Each year, the Nile brings down around 130 million tonnes of silt in its muddy flood, most of it soil from the Ethiopian highlands. For thousands of years, Ethiopia’s loss has been Egypt’s gain. While around 90 per cent of this silt was washed into the Mediterranean, between 10 and 15 million tonnes of it was deposited onto the Nile flood plain in annual layers about a millimetre thick. Since 1964, however, little silt has passed the dam. Instead it is accumulating in layers of about a metre a year in the southern, upstream half of Lake Nasser.

Although it may be a hundred years before silt seriously reduces the capacity of the huge reservoir, the dam’s critics say the loss of rich soil has already done irreparable damage to the fertility of the Nile valley and its delta. They claim that Egypt is now among the world’s heaviest users of chemical fertilisers – and, paradoxically, fertiliser factories are among the biggest users of Aswan’s power. Meanwhile, the critics add, many trace elements are in short supply in the soil.

Abu Zeid dismisses this analysis. Trace elements have always been in short supply, he says. He also insists that Egyptian research shows that Nile silt never provided farms with more than 6000 tonnes of potash and 17 000 tonnes of nitrogen a year, which are ‘insignificant’ amounts. He says that farmers use more fertilisers today because they are growing more crops, not to compensate for lost silt.

There is no doubt, however, that the loss of silt has created another land-use crisis. Egyptian brick makers once simply cut their raw material from the river banks, knowing that the river would replace it. But since 1964 they have had to buy up more and more land to stay in business. According to White, around 1000 square kilometres of river bank were eaten up in this way before the government called a halt in 1985, and forced brick makers to move into the desert.

Other critics are concerned about the fate of the Nile delta, which provides two-thirds of Egypt’s farmland. According to Daniel Jean Stanley and Andrew Warne, both of the Smithsonian Institution in Washington DC, the delta faces ‘widespread erosion’. In a paper in Science last year, they blamed the combined effects of the power of the Nile to erode its bed and banks, which is much greater if the river is not loaded with silt, and the reduced deposition of new material to replace that lost.

The Nile delta began to form only around 8000 years ago, when the level of the Mediterranean stabilised after a period at the end of the last ice age when it rose rapidly. Since then, its fields have probably been cultivated continuously for longer than any others on Earth. Though the delta has been retreating for almost 100 years, since the river’s first barrages began diverting the flow onto fields, it could now be undermined rapidly. To add to the consequences of silt not getting beyond the dam, there is the prospect of a renewed rise in sea level under the influence of the greenhouse effect, and the threat that waves from offshore will take their toll.

Abu Zeid agrees that coastal defences built in the 1940s have been overwhelmed since the completion of the dam. Fifty years ago, the village of Borg-el-Borellos lay at the mouth of one of the main channels out of the delta. Now the site is submerged about two kilometres out at sea. The Nile sediments that reached the sea were once washed eastwards along the coast, maintaining the sand bars in front of the delta’s large lagoons. Now the bars protecting Lakes Manzalla and Barullus are eroding. Their collapse would in turn flood low-lying delta farmland and aquifers with seawater.

Salty fields

As the sea advances, so does the desert. The Nile may no longer bring silt to fields, but it does bring salts, dissolved in the water. Modern irrigation systems leave the salt behind – about a tonne per hectare every year. With yields on a tenth of the delta’s fields already reduced by salt, Egypt has spent about $2 billion, much of it originating from by the World Bank, on installing a drainage network to remove the salt-laden water from some 2 million hectares. The total bill is more than the original cost of the dam itself. If the accumulation of salt is allowed to continue, fields will become toxic to plants, and the salt could eventually form a crust that would turn them back to desert.

Egypt has attempted to attack the encroaching desert on another front, by using the waters of the Aswan dam to annexe large areas of ‘new lands’ through irrigation. But so far the dream has proved an expensive nightmare. During the 1960s, Egypt built roads and canals, power lines and water pumping stations on more than 350 000 hectares of desert west of the delta. But the coarse, sandy soils of the area, known as Liberation Province, soon became waterlogged. By the end of the 1970s, only a third of those fields were still producing crops. ‘Unviable projects have been sustained as national fantasies,’ says Allan, a stern critic of the schemes to create the new lands. Investment should be channelled into improving existing fields in the delta, he says.

Undeterred by the dubious economics, Egypt is planning another assault on the desert. It wants to irrigate a further 600 000 hectares before the end of the decade, which will take an extra 9 cubic kilometres of water a year; a further 300 000 hectare are earmarked for similar treatment early in the next century. Even Abu Zeid admits that if only part of this scheme is carried out, Egypt will face serious shortages even if other water supply projects are completed. He calculates that the country’s annual water deficit will exceed 14 cubic kilometres by the year 2025.

To forestall such shortages, Egypt wants to perform the seemingly impossible and increase the flow of the Nile. Its first target was the Sudd, a vast and remote area of wetland in southern Sudan. The waters of the White Nile spend a year or more meandering through the Sudd, where roughly half the flow is lost to evaporation in the searing heat. The idea of digging a canal to bypass the Sudd, and so reduce evaporation losses, is credited to William Garstin, a British engineer who was head of public works in Egypt at the turn of the century. But it was 1978 before the ‘bucketwheel’, a laser-guided canal-cutting machine five storeys high, arrived on the banks of the White Nile to begin excavating the Jonglei Canal.

Abandoned site

Funded jointly by Egypt and Sudan, the canal was planned to boost river flows by an estimated 5 cubic kilometres a year; this dividend was to be shared equally between the two nations. But in 1984, with $100 million spent and the canal only half complete, Sudanese rebels attacked the construction camp, killing a worker and taking hostages. The site was abandoned and remains so today, with the civil war in southern Sudan showing no signs of abating.

And there is more bad news from the Nile’s headwaters. The 1959 agreement between Egypt and Sudan assumed an average annual flow of 84 cubic kilometres. But the river has not lived up to expectations. During the 1980s, the average was 76 cubic kilometres, and fell to 52 cubic kilometres per year between 1984 and 1987. The lowest flow was 42 cubic kilometres in 1984.

Moreover, some climate models predict that as global temperatures rise, rainfall in Ethiopia will fall, reducing the flow of the Nile, and evaporation rates will increase, especially from the Sudd and the lakes at the head of the White Nile. Declan Conway of the Climatic Research Unit at the University of East Anglia calculates that a reduction in rainfall of 10 per cent in the Blue Nile catchment will cut runoff into the catchment by 35 per cent.

‘Current demand,’ says Conway, ‘exceeds recent levels of supply.’ So far, Egypt has nonetheless been able to maintain the quantity of water it takes from the Nile, because Sudan does not use its full entitlement. Furthermore, Sudan’s reservoirs, built by British engineers in the 1930s, have silted up and lost much of their storage capacity.

But Egypt’s unfettered rule of the Nile’s flow through Aswan may soon be over. Despite the turmoil in Sudan, the government in Khartoum is intent on refurbishing its dams and building new ones. Sir Alexander Gibb & Partners, a British engineering firm, is advising Sudan on a plan to raise the Roseires dam on the Blue Nile, close to the border with Ethiopia, by 10 metres. This will both add to the capacity of the reservoir behind it and increase surface evaporation as a result.

More worrying still for Egypt’s water planners is the fact that Ethiopia may soon be making its own demands on the waters of the Blue Nile, drawing on proposals prepared by the US a generation ago. These include plans for reservoirs with a combined capacity of around 50 cubic kilometres, equal to the entire annual flow of the river in some years, and irrigation works capable of consuming more than 5 cubic kilometres of water a year.

In its anxiety to find more water, Egypt is looking again at ways to reduce evaporation from Lake Nasser. The unrelenting Saharan sun draws more than 2 metres of water from the surface of Lake Nasser each year, an average total loss, Abu Zeid estimates, of almost 14 cubic kilometres or more than twice the quantity lost from the Sudd. Reservoirs built outside Egypt’s borders in cooler places, such as in the headwaters of the river, where evaporation rates are a third of those on the arid Nile plain, would not suffer such heavy losses. In this hilly terrain the reservoirs could also be deeper, so a given volume of water stored there would have a smaller surface area.

Garstin knew this 90 years ago. He recommended the construction of large reservoirs in the headwaters. British hydrologists, who effectively ruled the Nile until the 1950s, backed Garstin’s proposals and opposed construction of the Aswan High Dam because they believed that its losses to evaporation would be unacceptably high. Now, with Egypt’s hydrological independence fading, the idea is set for a revival.

Dire threats

As recently as the beginning of 1990, Egypt uttered dire threats when it claimed Israeli engineers had been spotted in Ethiopia, planning to dam Lake Tana, the source of the Blue Nile. When Boutros Boutros Ghali, now secretary-general of the UN, was Egypt’s foreign minister he talked of war in the region over the Nile. But speaking at the Africa Water Summit in Cairo in 1990 he said: ‘We need more water, and there is no possibility of getting more water unless there is stability in the region.’ He called for a ‘closer working relationship with Ethiopia’.

The truth is that 50 cubic kilometres of Nile water stored in dams in Ethiopia could be Egypt’s salvation. That amount of storage would virtually eliminate the annual Nile flood, doing much of the job that the Aswan dam currently does. If a new agreement on the Nile waters gave Egypt assured access to the water, the size of Lake Nasser could be reduced, saving perhaps 10 cubic kilometres of Nile water from evaporation each year.

Allan points out that this would also expose large areas of the silt that has accumulated on the bottom of the southern half of the lake, mostly in Sudan, which could then be used as farmland. The main loss to Egypt would be the hydroelectric power generated at Aswan.

The solution may be a market in water rights, suggests Brian Grover of the Canadian International Development Agency, who organised a private conference on the Nile in February in Khartoum. ‘My personal feeling is that, before the 20th century is out, there will be important changes to the management of this vast natural resource.’ He believes that any new agreement must give all nations on the river some rights to its water. If some nations, such as Ethiopia, do not need their share, then they could sell it to Egypt. Allan, who believes pricing water will lead to its more efficient use, puts a tentative tag on Ethiopian water of 50 cents per cubic metre.

This cannot work if the talk continues to be of ‘water wars’ in arid parts of the world. International rivers such as the Nile may generate tensions, but the invaluable resource they represent can be managed efficiently only if there is stability and cooperation. The remorseless logic of hydrology dictates that water should be an agent for peace.

Fred Pearce is the author of The Dammed, published in 1992 by The Bodley Head, £14.95.