Basins and subbasins
The Niger River (4,180 km) is the longest river in West Africa and the third longest on the African continent. From its source in the highlands of Guinea, the river passes through Mali, Niger and Nigeria where it flows into the Gulf of Guinea in the Atlantic Ocean. The river drains a catchment area of over 2 million km2 and provides water to more than 100 million people. The Niger River Basin can be subdivided into three hydrographic regions (ABN 2007):
- The Upper Niger, including the headwaters in the highlands of Guinea and the Bani River headwaters in the low-altitude plateaus of southern Mali and northern Côte d’Ivoire, and further downstream the Inner Niger Delta in central Mali, where the Niger and Bani seasonally inundate the floodplains of the delta;
- The Middle Niger which runs east of the Inner Niger Delta through Mali and Niger into Nigeria;
- The Lower Niger, including the Bénoué River, the largest tributary of the Niger which originates in northern Cameroon, and the Niger Delta in southeastern Nigeria where the river flows into the Gulf of Guinea.
The Niger Basin divided into the Upper, Middle and Lower Niger. The Upper Niger in its turn is divided into two subbasins, the Upper Niger Basin (including the Bani headwaters) and the Inner Niger Delta.
Upper Niger Basin
In this Observatory the Upper Niger Basin refers to the upper catchment of the Niger in Guinea and the catchment of the Bani in Mali, which extends into the northern part of Cote d’Ivoire. The upper catchment of the Niger in Guinea comprises five main tributaries. These include the Tinkisso in the north, the Niger proper, and the Niandan, Milo and Sankarani. The Sankarani is situated partly in Mali and Guinea. The catchment of the Bani comprises three main tributaries: the Baoulé, the Bagoé and the Banifing.The confluence of the Niger and Bani is situated near Mopti but at high floods a part of the Bani water flows to the Niger via low lying depressions from Djenné to Kouakourou.
Both sub-basins together cover a surface area of 776.000 km2 of which the larger part is situated in Mali and Guinea and a much smaller part in Ivory Coast and Burkina Faso. The total catchment area of the Bani (129,000 km2) is nearly as large as the rest of the Upper Niger basin upstream of the Inner Niger Delta (147,000 km2).
The Upper Niger Basin and Inner Niger Delta
Inner Niger Delta
The Inner Niger Delta downstream of the Upper Niger Basin encompasses the floodplains of the Niger and a series of lakes in the north. The extent of the inundation zone on the map shows the maximum flooded area, based on IGN-maps from the 1950s (Zwarts et al. 2005, Zwarts & Hoekema 2013). This zones measures 36,470 km2, including 5340 km2 of levees, dunes and other islands within that area. The area actually inundated varies considerably between years (see flood dynamics).
The Inner Niger Delta may be subdivided in different regions. The southern delta includes the flooded parts south of the central lakes with the Niger and Diaka as main branches. Djenné (on the southern edge) and Mopti are the main settlements. In this area, north of Mopti, the ‘centre vide’ is situated, an elevated part of the delta which only inundates a the highest floods. The lower delta comprises the central lakes (Lac Débo, Walado Débo and Lac Korientzé) and surrounding floodplains. Youvarou and Akka are the main settlements. North of the lakes the character of the delta changes, with east-west running sand dunes interspersed with flooded areas. Main branches are the Niger and the Bara Issa. This part extends towards Tombouctou in the north.
In the northern part of the Inner Niger Delta a series of lakes fringes the west and east flank of the delta. The lakes on the west bank – including Lac Faguibine - are connected to the floodplain and filled with water most of the year, depending on the flood height in the delta. The water level in most of these lakes is managed to facilitate cultivation of the lakes. The lakes on the east bank are only inundated in case of very high floods and must be regarded as temporary lakes.
The Inner Niger Delta. The grey shading indicates the maximum inundation zone.
In Guinea the Upper Niger Basin is part of the administrative regions of Faranah and Kankan in Haute Guinée and Nzérékore in Guinée Forestière. Larger cities within the basin are Kissidougou and Kankan. In Mali the basin is situated in the regions of Koulikoro, Sikasso and Ségou. In Ivory Coast the headwaters of the Bani are situated in the administrative regions of Denguélé and Savanes. Larger cities along the river in Mali are Bamako, Ségou and San.
The Inner Niger Delta is situated entirely in Mali in three administrative regions: Segou, Mopti and Tombouctou. Larger cities are Mopti, Djenné, Diré and Tombouctou.
Administrative regions (on the level of cercles) for the Upper Niger Basin and Inner Niger Delta.