Chad Basin

Yobe River catchment area showing location of the Hadejia-Nguru wetlands.

The seasonal Korama River in the south of Niger does not reach Lake Chad. Nigeria includes two sub-basins that drain into Lake Chad. The Hadejia - Jama'are - Yobe sub-basin in the north contains the Hadejia and Jama'are rivers, which supply the 6,000 square kilometres (2,300 sq mi) Hadejia-Nguru wetlands. They converge to form the Yobe, which defines the border between Niger and Nigeria for 300 kilometres (190 mi), flowing into Lake Chad. About .5 cubic kilometres (0.12 cu mi) of water reaches Lake Chad annually. Construction of upstream dams and growth in irrigation have reduced water flow, and the floodplains are drying. The Yedseram - Ngadda sub-basin further south is fed by the Yedseram River and Ngadda River, which join to form an 80 square kilometres (31 sq mi) swamp to the southwest of the lake. There is not any significant water flow from the swamp to the lake.[10]

Chari River basin.

The Central African Republic (CAR) contains the sources of the rivers Chari and Logone, which flow north into the lake. The volume of water entering Chad annually from the CAR has decreased from about 33 cubic kilometres (7.9 cu mi) before the 1970s to 17 cubic kilometres (4.1 cu mi) during the 1980s. A further 3 cubic kilometres (0.72 cu mi) to 7 cubic kilometres (1.7 cu mi) of water annually flows from Cameroon into Chad via the Logone River. The Chari-Logone system accounts for about 95% of the water entering Lake Chad.[10]

The basin in the Nigerian section contains an upper aquifer of Early Pleistocene alluvial deposits that are often covered by recent sand dunes, varying in thickness from 15 to 100 metres (49 to 328 ft). It consists of interbedded sands, clays and silts, with discontinuous clay lenses. The aquifer recharges from run-off and rainfall. The local people access the water with hand-dug wells and shallow boreholes, and use it for domestic use, growing vegetables and watering their livestock. Below this aquifer, separated from it by a sequence of grey to bluish-grey clays from the Zanclean, is a second aquifer at a depth of 240 to 380 metres (790 to 1,250 ft). Due to intensive pumping, since the start of the 1980s the water levels in both aquifers has been lowered, and some wells no longer function.[13] There is a third, much lower, aquifer in Bima Sandstones that lies at a depth of 2,700 to 4,600 metres (8,900 to 15,100 ft).[14]

States in the Sahel / Savanna about 1750.

Humans have lived in the inner Chad Basin from at least eight thousand years ago, and were engaging in agriculture and livestock management around the lake by 1000 BC. Permanent villages were established to the south of the lake by 500 BC at the start of the Iron Age.[16] The Chad Basin contained important trade routes to the east and to the north across the Sahara.[10] By the 5th century AD camels were being used for trans-Saharan trade via the Fezzan, or to the east via Darfur, where slaves and ivory were exchanged for salt, horses, glass beads, and, later, firearms.[17] After the Arabs conquered North Africa during the 7th and 8th centuries, the Chad Basin became increasingly linked to the Muslim countries.[16]

Trade and improved agricultural techniques enabled more sophisticated societies, resulting in the early kingdoms of the Kanem Empire, the Wadai Empire, and the Sultanate of Bagirmi.[17] Kanem developed during the 8th century in the region to the north and east of Lake Chad. The Sayfuwa dynasty that ruled this kingdom had adopted Islam by the 12th century.[16] The Kanem empire went into decline, shrank, and during the 14th century was defeated by Bilala invaders from the Lake Fitri region.[18] The Kanuri people commanded by the Sayfuwa migrated to the west and south of the lake, where they established the Bornu Empire. By the late 16th century the Bornu empire had expanded and recaptured the parts of Kanem that had been conquered by the Bilala.[19] Satellite states of Bornu included the Sultanate of Damagaram in the west and Baguirmi to the southeast of Lake Chad.

Abéché, capital of Wadai, in 1918 after the French had acquired control.

The Tunjur people initiated the Wadai Empire to the east of Bornu during the 16th century. During the 17th century, the Maba people revolted and established a Muslim dynasty. At first, Wadai paid tribute to Bornu and Durfur, but by the 18th century Wadai was fully independent and had become an aggressor against its neighbors.[17] To the west of Bornu, by the 15th century the Kingdom of Kano had become the most powerful of the Hausa Kingdoms, with an unstable truce with the Kingdom of Katsina to the north.[20] Both of these states adopted Islam during the 15th and 16th centuries.[21] Both were absorbed into the Sokoto Caliphate during the Fulani War of 1805, which threatened Bornu itself.[22]

During the Berlin Conference in 1884-85 Africa was divided between the European colonial powers, defining boundaries that are largely intact with the present post-colonial states.[23] On 5 August 1890 the British and French concluded an agreement to define the boundary between French West Africa and what would become Nigeria. A boundary was agreed along a line from Say on the river Niger to Barruwa on Lake Chad, but leaving the Sokoto Caliphate in the British sphere.[24] Parfait-Louis Monteil was given charge of an expedition to discover where this line actually ran.[25] On 9 April 1892 he reached Kukawa on the shore of the lake.[26] During the next twenty years a large part of the Chad Basin was incorporated by treaty or by force into French West Africa. On 2 June 1909 the Wadai capital of Abéché was occupied by the French.[27] The remainder of the basin was divided by the British in Nigeria who captured Kano in 1903,[28] and the Germans in Kameroun. The countries of the basin regained their independence between 1956 and 1962, retaining the colonial administrative boundaries.

The area is badly affected by the Boko Haram insurgency, which began in 2009 and is centred on Borno State in northeastern Nigeria.

People at a coronation in Chad, 2005.

As of 2011, more than 30 million people lived in the Chad Basin. The population is growing rapidly.[10] Ethnic groups include Kanuri, Maba, Buduma, Hausa, Kanembu, Kotoko, Bagger, Haddad, Kuri, Fulani and Manga. The largest cities are Kano and Maiduguri in Nigeria, Maroua in Cameroon, N'Djamena in Chad and Diffa in Niger.[8]

The main economic activities are farming, herding and fishing.[10] At least 40% of the rural population of the basin is impoverished and experiences chronic food shortages.[29] Crop production based on rain is possible only in the southern belt. Flood recession agriculture is practiced around Lake Chad and in the riverine wetlands.[11] Nomadic herders migrate with their animals into the grasslands of the northern part of the basin for a few weeks during each brief rainy season, where they intensively graze the nutritious grasses. When the dry season starts they move back south, either to grazing lands around the lakes and floodplains, or to the savannas further to the south.[30]

During the period 2000-01, fisheries in the Lake Chad basin provided food and income to more than 10 million people, with a harvest of about 70,000 tons.[29] Fisheries have been managed traditionally by a system where each village has recognized rights over a defined part of the river, wetland or lake, and fishers from elsewhere must seek permission and pay a fee to use this area. The governments only enforced rules and regulations to a limited extent.[31] Fishery management practices vary. For example, on the Katagum river in Jigawa State, Nigeria, a village will have a water management council that collects a portion of each fisherman's catch and redistributes it among the villagers, or sells it and used the proceeds for communal projects.[32] Local governments and traditional authorities are increasingly engaged in rent-seeking, collecting license fees with the help of the police or army.[33]