Colonel Gaddafi is building the largest aqueduct the world has ever seen. The Great Man-Made River supplies the cities of northern Libya with drinking water from beneath the sands of the south. Pumping stations at Tazerbo and Sarir in the eastern Libyan Sahara raise water from deep aquifers and convey it northwards to Benghazi and Sirt through 1500 km of pipeline. In the west, well-fields in the Hamada al Hamra serve Tripoli, hundreds of kilometres to the north, with a cross-link to the eastern system via Sirt. Extensions to the oases of Al Kufra in south-east Libya and to Al Jaghbub near the Egyptian border are being planned. Each section of concrete pipe weighs 75 tonnes and is four metres in diameter, large enough to drive a truck through. According to elaborate conspiracy theories in the American press, the whole system was designed to allow the secret underground movement of troops.

The truth is both more ambitious and more disturbing. The Great Man-Made River effects a wholesale transfer of ancient aquifer reserves from beneath the sparsely populated Sahara to the urbanised northern coastal strip, where nearly all the agricultural land lies. The quality of water supply in the coastal cities, where most Libyans live, has been considerably improved by the scheme, and agricultural production has risen. By reducing the dependence of the coastal population on local aquifers, the aqueduct also helps reduce the intrusion of sea-water into the coastal water table, which has been taking place at a rate of between 100 and 200 metres a year because of over-extraction. When the project was begun in 1980, desalinating sea-water was prohibitively expensive, though since then costs have fallen rapidly: a new plant in Israel will be able to desalinate water for 53 cents per cubic metre. The cost of the Great Man-Made River is difficult to establish but it is somewhere between 50 cents and one US dollar per cubic metre. It is possible that Libya will now invest in desalination so as to diversify its water supply.

Apart from the diminishing cost advantage, the problem with the Great Man-Made River is that the ancient aquifers in the Sahara on which the scheme relies were formed in much wetter climates millions of years ago. They are non-renewable. Average rainfall in the regions of the well-fields today is between 10 and 20 mm per year. The lower limit for dry farming of cereals is about 200 mm a year. Every day, 4.5 million cubic metres of water are extracted and pumped through the Great Man-Made River system. Even in 1985, before it came on stream, Libya was using water at a rate of 374 per cent of its renewable supply. The availability of good water in the coastal cities can only accelerate population drift towards the urbanised coastal zone, making more and more of the population dependent on the project. Nobody is absolutely certain how large the aquifers are, and therefore how long they will last; estimates range from fifty years to two or three hundred. Nobody likes to talk about what will happen to the growing populations of the coastal cities after that.

Massive, prestigious water-engineering schemes are nothing new. In the sixth century BC, Polycrates, the tyrant of Samos, built an aqueduct that included a mile-long tunnel – a considerable feat. Aqueducts and monumental fountain-houses were also used by tyrants at Megara and Athens to secure popular favour. Aqueducts were a hallmark of Roman Imperial building policy, both in Rome and in the provinces; they supplied water to public fountains, baths and – for a fee – a few elite private houses. In Rome, private connections had to be authorised by the Emperor. The purpose of many such engineering schemes, over and above their actual utility, was to drum up political support and display wealth. Many were never realised: Julius Caesar’s plan to alleviate flooding in Rome by cutting a relief canal around the back of the Janiculum Hill was abandoned after his assassination. In ad 15, a scheme to divert tributaries of the Tiber in order to reduce the amount of water flowing through Rome was defeated after opposition from representatives of Florence, Terni and Rieti, the towns most closely affected by the proposed diversions – a rare example of local interests prevailing over those of a larger, more distant authority.

In the late 19th century, the French planned to link the Tunisian chotts (salt lakes) of the Northern Sahara with the Mediterranean. A vast inland sea in southern Tunisia and along the southern edge of the Aurès mountains in Algeria would have facilitated trade and troop movements in French North Africa, and increased the humidity, and therefore fertility, of the region. Jules Verne’s L’Invasion de la mer (1905), published in English for the first time last year, is based on the scheme; the conflict it evokes between the potential benefits of technology for urban industrialisation and the disruption caused to traditional lifestyles has dogged large-scale water engineering schemes throughout history.*

Strabo wrote about wars in the second and first centuries BC between the Salassi, a tribe in the Aosta valley of Northern Italy, and the people who farmed the plains below them; the Salassi were diverting the entire flow of the Dora river for use in mining operations, leaving the farmers with no water for irrigation. The Salassi were driven out of the region into mountain areas higher up; but they still controlled the headwaters of the river, and made their living selling water to the Romans who took over the mining concessions.

More recently, the Six-Day War of June 1967 was the culmination of escalating tension and conflict over water rights in the Jordan basin. Israel and Jordan had both initiated unilateral schemes for the River Jordan headwaters. Jordan diverted part of the Yarmouk river, a major tributary, to irrigate the east bank, while Israel’s National Water Carrier diverted water from the Jordan above Lake Tiberias, for distribution on the coastal plain and in the Negev desert. Israel also planned to pump water out of Lake Tiberias itself. The riparian Arab states objected, and in 1960 the Arab League proposed a retaliatory scheme to divert the Hasbari and the Banias, upper Jordan tributaries, through Syria into Jordan, bypassing the point of diversion to Israel’s National Water Carrier. Israel declared that this would be an attack on one of its means of livelihood and would be construed as a threat to peace; the Arab scheme, they claimed, denied Israel’s right to exist. At the Alexandria Summit in September 1964, by which time Israel had already begun test pumpings on the first stage of the National Water Carrier, the Arab states decided to go ahead with the diversion scheme, to respond to aggression against one of them as aggression against all, and to establish the Palestine Liberation Organisation. Clashes ensued along the Syrian-Israeli border in late 1964 and the first half of 1965, until work on the diversion stalled. In 1966, Israeli air strikes hit the diversion works on the Banias-Yarmouk canal in Syria, and there were dogfights over Lake Tiberias. Tension mounted during 1967, as Jordan resumed work on the Mukheiba Dam to create a reservoir on the Yarmouk. In May, Egypt blockaded the Straits of Tiran and massed troops on the Israeli border in Sinai. Jordan signed a defence pact with Egypt and allowed Iraqi and Saudi troops to enter its territory.

On 5 June 1967, Israel launched a pre-emptive strike, and six days later its victory had reversed the balance of water resources in the Middle East. Its occupation of the Golan Heights gave it control over the Banias headwaters. Lebanon and Syria lost their riparian status, and played no further part in the dispute over the Jordan basin. Israel’s occupation of the West Bank gave it important groundwater resources; by contrast, Jordan lost a third of its population and agricultural land, accounting for 45 per cent of its GNP. Since 1967, the Arab goal has changed: curbing Israel’s economic development is no longer a possibility and the aim is to secure an equitable distribution of the Jordan-Yarmouk waters.

The worst wars of this century are likely to be fought over water rather than oil. The current focus on international terrorism does nothing to allay that fear; indeed, the long and arduous process of reconstructing Afghanistan will be made all the more difficult by the effects of the three-year drought the country has suffered. Twelve per cent of the world’s population live in regions with scarce water resources; in the Middle East and North Africa the figure is 71 per cent. Turkey’s programme of dam construction on the Euphrates has angered its downstream neighbour Syria, whose own dams have in turn affected water use in Iraq.

Nonetheless, no wars have been fought over water in the Middle East and North Africa since the 1960s, perhaps because of the phenomenon of ‘virtual water’: countries short of water import foodstuffs that require a lot of water to produce, paying for them with exports of water-efficient products. A thousand tonnes of water (1000 cubic metres) are required to produce one tonne of wheat; 16,000 cubic metres of water are needed to produce a tonne of meat. The Middle East and North Africa import 50 billion cubic metres a year of virtual water – an amount equivalent to the annual flow of the Nile into Egypt. But virtual water doesn’t figure when water problems are discussed by politicians: to draw attention to it would be to advertise a country’s dependence on external trade links, and self-sufficiency is the ideal promoted by the politicians of the region.

There has long been a close relationship between the control of water resources and the exercise of political or economic power. Ancient Mesopotamian agriculture relied on networks of irrigation canals which had to be cleared of silt each year. In the command economy of the period, this work was organised by the state. Teams of scribes worked out the labour requirements using the sort of exercise familiar from our own maths schoolbooks, although they wrote in cuneiform and calculated in base 60. Examples survive on clay writing tablets: ‘Given 36 cubits of irrigation ditch of trapezoidal cross-section (3 cubits at the top, 2 cubits at the bottom, 2 cubits deep), which has silted up to a depth of ½ cubit, how many man-days of labour do you need to clear it out, assuming each man can shift 24 cubic cubits of mud per day?’ Ancient Egypt also maintained central control over water. Annual levels of tax were determined each year by the Nilometer, a device for measuring the depth of the Nile flood. The higher the flood, the higher the tax, as more land would be cultivable once the floodwaters receded.

In the 1830s, half a century before the plans for the Saharan sea, the French armies fighting in Algeria were accompanied by archaeologists whose brief was to discover how the Romans had held the territory. The first questions were: where were the roads, and where the forts? Once Algeria was brought under French control, attention turned to agricultural production and the question of how the region had managed to become the bread-basket of ancient Rome. Commissions of inquiry were established to investigate and report on Roman aqueducts and irrigation works with a view to putting them back into service. Sometimes the results were distorted by wishful thinking – a 40-km Roman frontier ditch on the edge of the Sahara was mistaken for an irrigation system – but it was clear that lessons could be learned from past experience.

That doesn’t always happen. In the Fazzan – a group of oases in the Libyan Sahara to the south of the well-fields serving the western branch of the Great Man-Made River – archaeological evidence shows that in the first few centuries ad the area was home to the flourishing civilisation of the Garamantes, a Libyan tribe that controlled virtually all trans-Saharan trade. Recent British fieldwork, led by David Mattingly, has demonstrated that this civilisation, in an area where average annual rainfall is less than 10 mm, practised intensive agriculture supported by qanats (locally called foggaras): underground tunnels that tapped an aquifer in the slopes of an adjacent cliff, channelling water to the oasis floor. (Probably invented in Persia between the eighth and sixth centuries BC, under the Assyrian or Achaemenid Empires, the technique spread to Oman and Yemen, westwards to Egypt, through the Sahara to Fazzan and then, perhaps in the early medieval period, to Algeria and thence to Morocco and even Spain, from where, much later, the conquistadores introduced it to Mexico. Qanats spread eastwards too, perhaps along the Silk Route, to Afghanistan – where they are called karez – eventually reaching China. During the US bombing campaigns last year, the dry karez in drought-afflicted Afghanistan were used by the Taliban both for refuge and for troop movements – for which they are much better suited than Libya’s Great Man-Made River.)

The foggaras in the Sahara were dug between pairs of vertical access shafts only a few metres apart. Their course and gradient can be monitored on the surface, enabling a tunnel of several kilometres to be dug with relatively simple surveying equipment. In Fazzan, more than 550 foggaras have been traced, some up to six kilometres long, and dated to the Garamantian period; the technique must have reached the area in the final centuries BC along desert trade routes from Egypt. Over several hundred years the foggaras depleted the water reserves in the aquifer: the fields could no longer be watered, the population shrank, and labour was no longer available to maintain the foggaras by digging out silt and clearing rockfalls from the channels. People went over to using wells, which could irrigate only much smaller areas. The population declined further, the Garamantes were unable to retain their grip on trans-Saharan trade, and settlement in the area diminished drastically.

Since the 1970s, with the introduction of pumped wells and the building of a new road to the border with Niger, the Libyan population has returned to ancient levels. Now there is a Government scheme to plant two million palm trees, which will require water, by the year 2020. Yet while the foggaras proved to be unsustainable in the very long term, wells pumping ancient water from deep aquifers are unsustainable even over the short term. Every year, they have to be deepened to chase a receding water table; in some areas water is tapped at a depth of 100 metres or more, where it was available two metres down in the early 19th century. The pumped irrigation for the new palm plantations has already depleted natural water reserves so that older palm groves, where tree-roots used to be able to reach groundwater, have died off. The situation may well worsen if even more water is taken from the aquifers for the Great Man-Made River to the north. Within a generation or two, human settlement in the Fazzan could again go the way of the Garamantes.

Monolithic high-tech schemes like the Great Man-Made River are extremely expensive and rely on a single method of supply; often they are political showpieces as much as responses to real needs. The names make this clear: the Aswan High Dam has turned the Nile between the first and second cataracts into Lake Nasser; Syria has its Lake Assad on the Euphrates. These large modern dams do enormous damage to local ecology and archaeological heritage, and lead to the forced displacement of inhabitants. The Birecik Dam on the Euphrates in Turkey has flooded much of the site of the Roman city of Zeugma, with its extraordinary mosaics, and driven thirty thousand Kurds from their homes. Yet examples from the past suggest that such dams will ultimately fail: they will be undermined, or outflanked, by progressive erosion of the valley sides; or silting will reduce and eventually exhaust the capacity of the reservoirs they create; or they will be overwhelmed by violent floods and breached.

The first three problems can be staved off by lengthening the dam, strengthening the downstream face, or heightening the dam; but in the end, nature will win. North Africa and the Middle East are littered with the remains of ancient dams, dating from the Bronze Age, or from the Roman, Byzantine and early medieval periods, which show signs of having been lengthened, heightened or buttressed before their ultimate failure. The late Roman dam at Homs in Syria, made of concrete, is two kilometres across. Modern dams may be even larger, but that doesn’t make them immune. The extent to which any of this is taken into consideration in the planning of modern dams is unclear; governments do not publish details of their expected lifespan. Modern dam schemes require central financing, and decisions on construction are often influenced by the prospect of short-term political gain and financial benefits for the construction firms. Even the agricultural benefits are localised: they provide irrigation and hydroelectricity near the reservoir, but have a negative impact on communities further downstream. If the dam fails, the cost of repair must be borne by central government, not the communities that rely on the water. Pumped wells, for all their problems, present a better alternative, distributing sources of supply, spreading the risk and keeping the costs of technology low enough for local farmers to take control of irrigation.

The traditional approach to settlement in arid regions has been to live in small communities so as to limit the impact on water resources in any one location – hence the foggara-fed settlements strung out at intervals along a 160 km strip of the Garamantian Fazzan, or the Roman-period agricultural exploitation of the Libyan pre-desert on the northern margins of the Sahara, south of Tripoli and Lepcis Magna. Here, in the 1980s, the Libyan Valleys Project – a Unesco-sponsored Anglo-Libyan archaeological survey – investigated and mapped hundreds of ancient sites in a zone where average annual rainfall varies from 100 mm to a tiny 25 mm. The project was supported by Gaddafi: ‘If archaeology is to be practised in this country at all,’ he is reported to have said, ‘let it at least be relevant to the needs of the Libyan people.’ He suggested an investigation of the archaeology of the Valleys region, where he himself had grown up among the pre-desert tribesmen, and had noticed the ruins of a vanished settled population.

The project’s brief was to find out how such a population could have been sustained in antiquity. Had the climate changed? Had special agricultural or water conservation techniques been used? If so, could they be revived? The survey investigated villages, farms, fortified farms and forts with agricultural buildings around them – all testament to a high level of agricultural production. Some farms had olive presses, suggesting that capital had been invested to produce a surplus for sale, not merely for subsistence. Paleobotanical evidence from some sites indicated a wide range of crops – olives, wheat, barley, lentils, peas, pistachios, grapes, figs, even watermelons. The Romano-Libyan farmers had controlled run-off to make the most of the region’s erratic and unpredictable rainfall.

The little rain that the area receives falls in cloudbursts on only a few days of the year. The parched ground cannot absorb it, and it sheets off the plateaux into the wadis (seasonal watercourses), causing violently erosive flash floods. All the settlements were along the banks of the wadis, often at the confluence of tributaries. Stone walls or dams at frequent intervals (every hundred metres or so) across the wadi floor checked the force of the flash floods, retaining the water and causing it to deposit silt washed down from upstream. The water sank into the silt, and was retained longer than it would have been in an open reservoir subject to evaporation. Crops were grown in the fertile earth in the wadi bottom, and each flash flood brought down new soil. Walls on the plateau edge steer additional run-off water, which was also channelled into cisterns to provide drinking water. The system relied entirely on renewable resources – the annual rains – and it broke down for socio-political reasons rather than as a result of climate change or the exhaustion of water resources. Unlike the large concrete dams of northern Libya or Syria, the small-scale check dams were built of stone and earth, and could be easily and cheaply repaired each year.

Similar techniques were used in Israel’s Negev desert in antiquity, and have been resurrected there, on a very limited scale, in recent decades. But all too often the potential for trapping and storing rainwater is overlooked in modern schemes, whether agricultural or urban, and a single groundwater or river source is tapped instead. In the Roman period, almost every city in the Mediterranean was heavily dependent on rainwater cisterns, storing run-off from the roofs and courtyards of houses. At some stage in their history, many, perhaps most, of these cities acquired an aqueduct fed by a spring, a river, or by groundwater, but the domestic cisterns remained in use. The public aqueduct supplied water for drinking and bathing, and the rainwater in private cisterns was used for laundry and washing the floors. The use or re-use of different qualities or purities of water for different purposes was a vital principle in the ancient world, but it is one that we have largely forgotten today: now we purify all water to drinking standard, then decide whether to drink it or flush the toilet with it. The treatment and re-use of waste water is now showing signs of increasing: more than ten per cent of the water used in Israel has been recycled. When, in the late 1990s, Linacre College in Oxford opened a new accommodation block, its use of waste bathwater to flush toilets was hailed as an ecologically sound innovation. The Romans, for their part, were flushing latrines with the outflow from their public baths 2000 years ago.

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