Libya's geography: a land without rivers that drinks from under the Sahara

How three regions divide Libya's land

Cyrenaica in the east covers 51% of Libya, Fezzan in the south-west 33% and Tripolitania in the north-west 16%, by the figures Wikipedia carries from the Library of Congress country study. Cyrenaica runs south from the Jabal al Akhdar through a barren grazing belt into the Sahara as far as Kufra, while Tripolitania stops short of the deep desert. Fezzan was administered separately under Italian rule and again in the federal period of the monarchy.

Between the two settled coasts the desert reaches the shore. Around the Gulf of Sidra the Sahara borders the sea, in the stretch Britannica calls the Sirte Desert and Wikipedia the Sirtica, with the Jifarah Plain and the Nafusa Plateau to the west of it and the Marj Plain and the Jabal al Akhdar to the east.

The FAO's 2016 country profile gives Libya's area as about 1.76 million km², about 95% of it desert. The coastline measures 1,770 km by the CIA figure Wikipedia reproduces, and a 2018 paper by zoologists at the University of Tripoli and their colleagues gives 1,900 km. Libya also claims a closing line across the Gulf of Sidra at 32°30′ north.

The land borders total 4,348 km. The country study, as Wikipedia quotes it, found no natural frontier on the Tunisian or the Egyptian line and frequent crossings over both, while the borders of Fezzan are seldom crossed because the desert around them is almost empty.

Much of the southern line was drawn under Italian rule. Egypt ceded the Kufra and Jarabub districts on 6 December 1925, the Anglo-Egyptian Condominium handed over the Sarra Triangle in 1934, and the Mussolini-Laval agreement of 1935, which France never ratified, added the Aouzou Strip. Libya occupied the strip in 1973 and withdrew in 1994, after the International Court of Justice gave judgement on 13 February that year; Britannica reports the ruling as finding that the territory belonged to Chad.

Where rain falls on Libya's northern uplands

From October to March westerly winds bring storms and rain across the north, and inland, Britannica notes, most of the year's rain falls on a few days between November and January. The FAO's 2016 profile names two areas whose average passes the 250 to 300 mm a year it takes as the minimum for rain-fed farming: the Jabal Nafusa with the Jifarah Plain in the north-west, and the Jabal al Akhdar in the north-east. About 93% of the land receives under 100 mm, and Wikipedia's geography article puts the share with enough rain for settled agriculture at less than 2%. Even in the north the rain is erratic. Floods in 1945 left Tripoli under water for several days, and two years later a drought cost thousands of head of cattle.

What the north-western plain and plateau hold

The Jifarah Plain is a triangle of sand dunes, salt marshes and steppe rising from the sea to about 300 m. Wikipedia gives its area as about 15,000 km² and Britannica as about 26,000 km². Britannica places most of Libya's people on it, along with Tripoli, which averages about 380 mm of rain a year. About 120 km inland the plain ends at the escarpment of the Nafusa Plateau, a limestone massif running about 340 km from Al-Khums on the coast to Nalut on the Tunisian border, which west of Tarhuna climbs steeply to between 450 and 975 m. The grey-brown soils of plain and plateau are fertile, though over-irrigation has made them saltier.

What the Green Mountain in the east holds

The Marj Plain curves in a crescent about 210 km long between Benghazi and Derna and reaches at most 50 km inland. Behind it the Jabal al Akhdar rises steeply to about 600 m, then stretches some 30 km inland to nearly 900 m. The name means Green Mountain, for its cover of pine, juniper, cypress and wild olive, and on the seaward side Britannica describes a low, fairly dense maquis of juniper and lentisc that grows sparser and more stunted south of the crest. Benghazi, below it, averages about 250 mm of rain a year. The FAO records winters cold enough on both uplands for snow on the hills, and Wikipedia notes that the springs best suited to development break out along the scarps of the two.

What covers the Saharan plateau

About nine-tenths of Libya is Saharan plateau, by Britannica's measure, and about half of that is sand. Beneath the whole country lies Precambrian basement rock, mantled with marine and wind-borne deposits. South of the Nafusa the Al-Hamra Plateau has bare outcrops up to 820 m. In the centre Al-Haruj al-Aswad is a basaltic plateau about 800 m high, strewn with angular stone and crowned by volcanic peaks, and east of Sabha lies the volcanic crater of Waw an Namus.

Fezzan holds long depressions and basins with wadis and oases in them, and much of it is covered by two dune seas, the Idehan Ubari and the Idehan Murzuq. Mobile dunes in the Murzuq desert and in the Libyan Desert reach 90 m. The FAO lists Gaberoun, Mandara and Mafo among the lakes of the Ubari sand sea. In the east the Calanshio Sand Sea is a western lobe of Egypt's Great Sand Sea, and the Kufra group of oases, Tazerbo, Rebiana and Kufra, lies in unconnected shallow depressions.

The high ground is at the edges. Near the Chad border the Tibesti massif rises above 2,200 m, and Bikku Bitti, on the border itself, reaches 2,267 m. In the south-east corner the granite massifs of Arkenu, Uweinat and Kissu are older than the sandstones around them, and Mount Al-Uwaynat reaches 1,934 m on the border Libya shares with Egypt and Sudan. The rock-art sites of the Tadrart Acacus were inscribed as World Heritage in 1985 and placed on UNESCO's danger list, with Libya's four other sites, on 14 July 2016.

The low ground is salt. Sebkhas form behind the coastal dunes at Tawurgha, at Zuwarah and on the Benghazi Plain, and Sabkhat Ghuzayyil in the north-east lies 47 m below sea level. In 2011, 0.99% of the territory was arable and 0.19% under permanent crops, by the CIA figures Wikipedia carries.

Why no river runs anywhere in Libya

Libya drains by wadis, which Britannica describes as filling with flash floods in the rains and then drying out or shrinking to a trickle. It names Wadi Zamzam and Wadi Bayy al-Kabir as the main systems, both reaching the sea on the western shore of the Gulf of Sidra. People settle along the wadis because the soil in their beds suits farming and the water table beside them suits wells, and in many of them, Wikipedia's account adds, that water table is falling fast.

Standing water is scarce, and salty. Wikipedia counts about twenty perennial lakes, all brackish or salty, and the FAO notes that the 23rd of July lake at Benghazi is in fact a lagoon. The government has dammed the wadis to store water and hold back floods. The FAO counts 19 dams with a combined capacity of 389.89 million m³ in 2015, but an average annual storage of only about 61 million m³.

What rain renews each year is small. The FAO puts it at 700 million m³ a year, 200 million of surface water and about 600 million of groundwater less 100 million counted twice, with nothing flowing in from outside. That came to 112 m³ per person in 2015, against the 500 m³ the FAO treats as the threshold of absolute scarcity. Even the national rainfall depends on who measures it. The FAO gives a long-term average of 56 mm a year, and the World Bank's Climate Change Knowledge Portal, working from the ERA5 reanalysis, gives 21.72 mm for 1995 to 2014.

How old the water beneath the Sahara is

The FAO describes Libya as relying almost completely on fossil groundwater. Of its five major aquifers only the shallow coastal ones, the Jefara and the Jabal al Akhdar, are recharged by rain, along with part of the Hamada. South of 29° north the rest belong to sedimentary basins whose water was stored during the Quaternary.

Britannica dates the water of the Nubian Sandstone Aquifer System at anywhere from 10,000 to 1,000,000 years. It seeped into the sandstone before the end of the last ice age, when the Saharan region had a temperate climate, and it is not being replenished. The Sarir-Kufra aquifer is part of that system, of which Libya holds 34% by an IGRAC figure in the FAO profile, with the rest under Chad, Sudan and Egypt, and the Hamada belongs to the North Western Sahara Aquifer System, shared with Algeria and Tunisia. A joint authority for the Nubian system was set up in 1992 with its headquarters in Tripoli.

Oil exploration found the deep water. Britannica places the first find in the Al-Kufrah area in the 1950s, during drilling for oil, and Wikipedia's article on the pipeline dates it to 1953. Meanwhile the coastal aquifers were falling. From the 1960s pumps were needed where wells and traditional tools had been enough, by the FAO's account, and the Middle East Institute dates seawater intrusion into the coastal aquifers to the 1930s.

Drawing water from beneath the desert is an old practice here. The FAO's profile records that the Garamantes of Fezzan irrigated their oases from at least 500 years before the current era through foggara, underground channels running through thousands of kilometres of tunnels and kept open through vertical wells.

How the Great Man-Made River carries water north

Muammar Gaddafi laid the pipeline's foundation stone at Sarir on 28 August 1984, and the government called it the "Eighth Wonder of the World". Since 1991 it has supplied cities and farms in the north that had depended on desalination plants and on declining rain-fed aquifers near the coast.

How the pipeline was built in phases

Hundreds of wells at Tazirbu and Sarir pump from about 500 m into a double pipeline, which reached a holding reservoir at Ajdabiya in 1989 and ran on west to Sirte and north to Benghazi, where the first phase was celebrated in 1991. Britannica gives it a capacity of 2 million m³ a day over some 1,600 km. The western system draws on three well fields in the Jabal al-Hasawinah and began supplying Tripoli in 1996, with a design capacity of 2.5 million m³ a day. A third phase, completed in 2009, raised the eastern system to 3.68 million m³ a day and added a branch to Tobruk from wells at Al-Jaghbub. With the two phases still planned, south to Kufra and from Ghadames to the coast west of Tripoli, the network would carry about 6.5 million m³ a day through some 4,000 km of pipe.

The pipe sets the scale. Each of the 250,000 sections laid in the first phase is 4 m across and 7 m long, made of layered steel-reinforced prestressed concrete in factories at Brega and Sarir that opened on 28 August 1986. Cranes built for the job lowered them into trenches 7 m deep, and the joints were sealed with giant rubber O-rings and cement grout. One of the asphalt-lined reservoirs at the distribution points is more than 1 km across and holds up to 24 million m³.

Estimates of the cost run from US$20 to 25 billion in the Middle East Institute's account to over US$30 billion in the FAO's, all of it from national funds. Water meant first for irrigation went mostly to the towns. The FAO cites the Environment General Authority's 2013 figure that 98% of the transferred water goes to municipalities. In 2012 total withdrawals came to 5,830 million m³, 83% of them for agriculture, and groundwater, fossil water included, supplied over 95%.

How long the fossil water can last

Estimates disagree widely. Some Libyan officials have said thousands of years, while critics cited by Britannica say the system might not last through the 21st century. The FAO's range runs from 50 years to over 4,000, depending on how much is drawn and from where, and the Wikipedia article gives a thousand years at 2007 rates or, by other estimates, 60 to 100.

Desalination is the alternative Britannica names. It began in Libya in the early 1960s, and the FAO counts more than 400 plants with an installed capacity of 226.3 million m³ a year in 2006 but production of about 70 million m³ in 2012. UNICEF reported in 2022 that the plants were running at 27% of capacity.

The network itself has been damaged since 2011. A NATO air strike hit the Brega pipe plant on 22 July 2011, 101 of the 479 wells on the western system had been dismantled by July 2019, and on 10 April 2020 an armed group seized a station controlling the flow to Tripoli and cut water to over two million people. In 2022 UNICEF put the wells out of service after repeated attacks at about 190.

What happens when heavy rain does fall

Storm Daniel reached its peak over north-eastern Libya on 10 September 2023. Between 150 and 240 mm fell on several cities, and Al-Bayda recorded 414.1 mm in the 24 hours from 8 a.m. that day, which Libya's National Meteorological Centre called a new rainfall record. The centre had issued warnings 72 hours ahead.

Two dams stood on the Wadi Derna: the Mansour, or Abu Mansour, holding 1.5 million m³, and the Derna, or Belad, upstream, given 22.5 million m³ by one source and 1.5 million by another. The Yugoslav firm Hidrotehnika-Hidroenergetika built both between 1973 and 1977. They were badly damaged in a storm in 1986, cracks were reported in 1998, and Derna's deputy mayor said they had not been maintained since 2002.

Both failed in the night. About 30 million m³ of water came down the wadi, which overflowed by 50 m on each side, and reached Derna shortly before 03:00 on 11 September. At least 5,923 people were killed in Libya, most of them in and around the city, and 30,000 were displaced, by the figures Wikipedia collects. The wadi had seen four major floods between 1942 and 2011. At Cyrene the same rain buried structures in mud and uncovered parts of the site that had never been excavated.

How heat and the ghibli shape the interior

Inland the summers are long and extremely hot, and clear skies and very dry air give wide swings between day and night. Sabha averages a little over 10 °C in January and a little over 30 °C in July, with about 10 mm of rain a year, and at Uweinat, as of 2006, the last recorded rain had fallen in September 1998. A reading of 58 °C at Aziziya, south-west of Tripoli, on 13 September 1922 was long accepted as a world record, and in September 2012 the World Meteorological Organization ruled it invalid.

The ghibli is the hot, dry wind from the south. It blows over the whole country several times a year, for one to four days in spring and autumn, and carries enough dust to turn the sky red and cut visibility to under 18 m.

For the country as a whole the World Bank's portal gives a mean annual temperature of 22.45 °C for 1995 to 2014, warming at 0.37 °C a decade since 1970, and a median projection of a further 1.79 °C by 2040 to 2059 under the high-emission SSP3-7.0 scenario. UNICEF's 2022 analysis cites the Global Facility for Disaster Reduction and Recovery in rating water scarcity a high hazard across the country, with droughts expected about every five years.

Where Libya protects its plants and animals

In wet years the coastal plains carry herbs and annual grasses, asphodel and jubule the most noticeable in Britannica's account. The steppe has saltwort and spurge flax in isolated pockets, and date palms grow in the southern oases. Britannica's wild animals include the jerboa, the fennec, jackals and gazelles, and Wikipedia records that the addax and the scimitar-horned oryx have declined through hunting.

The first protected area dates from 1975 in Wikipedia's account and from 1978 in a 2018 paper by Khaled Etayeb and colleagues, which describes Al-Kouf National Park, west of Al Bayda, as 20 km of coast, dunes and seasonal brackish lagoons with mountain forest behind them. By 2011 there were 13 sites, two of them marine areas declared that year.

The paper puts the 13 at about 18% of Libya's area, although the hectares in its own table add up to a little over 300,000, which is under 0.2%. It also records what happened to them after 2011. Al-Kouf was seized by local people claiming the land as theirs, Al-Gharabolli was protected only by a temporary army occupation, and Farwa had no administration or management plan. Khaled Ettaieb, quoted in Wikipedia's article on Libya, said of the poaching since 2011 that "More than 500,000 birds are killed in this way each year".