Africa's Inland Deltas

Inner Niger Delta

For four months each year during the rainy season, floodwaters spill over the banks of the Niger and Bani Rivers and the Inner Niger Delta swells to an area of about 20,000 km2. The swamps, lakes, and channels of the delta provide vital habitat for migratory Palearctic birds and West African manatees. The delta is also an essential resource for Malians, supporting livelihoods in fishing, farming, and pastoralism in an otherwise arid country. These floodplains support the highest livestock density in Africa, and are increasingly threatened by a variety of anthropogenic pressures and unsustainable uses.



The Inner Niger Delta is located in central Mali in the semi-arid Sahelian zone, just south of the Sahara Desert. The huge dunes of the Erg Ouagadou funnel the waters of the inner delta north and east through Mali. A diverse mix of channels, swamps, and lakes, the delta expands to cover 20,000 km2 during the rainy season and contracts to 3,900 km2 during the dry season (Welcomme 1986). The delta extends for 425 km with an average width of 87 km, tapering into a braided river near Timbouctou where the Niger River curves to the east. The floodplain is remarkably level, dropping only 8 m over its course (Hughes and Hughes 1992). Delta topography is a complex mix of submerged lower areas and higher, unflooded areas known as tougérés. The floodplain consists of a vast network of river channels with leveés separated by low, clay-based floodplains. As waters flow through the delta, they pass over Pleistocene and recent alluvium overlying Paleozoic sandstone (Hughes and Hughes 1992).

The floodwaters of the delta come primarily from the Niger River, its main tributary the Bani River, and smaller streams that flow down from the Dogonland Plateau. The Niger River is the longest river in West Africa and the third longest in Africa. Originating in the Fouta Djalon highlands of Guinea, the river extends for 4,100 km before flowing into the Atlantic Ocean on the Nigerian Coast. The Bani River is 1,100 km in length with sources in Côte d’Ivoire and Burkina Faso. Dogonland streams provide an insignificant contribution to the delta but do fill the southwestern lakes (Hughes and Hughes 1992). Dry, landlocked Mali is completely dependent on these rivers for its water resources (FAO 1997).


The Okavango Delta (or Okavango Swamp), in Botswana, is the world's largest inland delta.

“ "Where all this water goes is a mystery", Aurel Schultz, 1897 ”

The area was once part of Lake Makgadikgadi, an ancient lake that dried up some 10,000 years ago. Today, the Okavango River has no outlet to the sea. Instead, it empties onto the sands of the Kalahari Desert, irrigating 15,000 km² of the desert. Each year some 11 cubic kilometres of water reach the delta. Some of this water reaches further south to create Lake Ngami.

The water entering the delta is unusually pure, due to the lack of agriculture and industry along the Okavango River. It passes through the sand aquifers of the numerous delta islands and evaporates/transpirates by leaving enormous quantities of salt behind. This precipitation processes are so strong that the vegetation disappears in the center of the islands and thick salt crusts are formed.

The waters of the Okavango Delta are subject to seasonal flooding, which begins about mid-summer in the north and six months later in the south (May/June). The water from the delta is evaporated relatively rapidly by the high temperatures, resulting in a cycle of cresting and dropping water in the south. Islands can disappear completely during the peak flood, then reappear at the end of the season.


Elephants in the Okavango Delta seen from the dubious safety of a makoro (small boat).

The Okavango Delta has been under the political control of the Batawana (a Tswana sub-tribe) for several hundred years. Most Batawana, however, have traditionally lived on the edges of the Delta. Small numbers of people from other ethnic groups such as Ovaherero and Ovambanderu now live in parts of the Okavango Delta, but since the majority of the members of those groups live elsewhere and the habitation is recent they are not considered as part of the Okavango Delta peoples. There are also several Bushmen groups represented by a handful of people. These groups were decimated by diseases of contact in the middle part of the 20th century, and most of the remaining members have intermarried with the ||anikwhe.



My Note: I am totally amazed by the reality of an inland delta. In school, I was taught that all rivers flowed to the sea. I only recently learned about rivers that flow into desert areas with life giving waters. Please take the time to find Mali and Botwswana on the map of Africa.