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Two shakes. Niger River

The Niger River is a relatively "clear" river, carrying only a tenth as much sediment as the Nile because the Niger's headlands are located in ancient rocks that provide little silt.[3] Like the Nile, the Niger floods yearly; this begins in September, peaks in November, and finishes by May.[3]

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An unusual feature of the river is the Inner Niger Delta, which forms where its gradient suddenly decreases.[3] The result is a region of braided streams, marshes, and lakes the size of Belgium; the seasonal floods make the Delta extremely productive for both fishing and agriculture.[4]

The river 'loses' nearly two-thirds of its potential flow in the Inner Delta between Ségou and Timbuktu due to seepage and evaporation. All the water from the Bani River, which flows into the Delta at Mopti, does not compensate for the 'losses'. The average 'loss' is estimated at 31 km3/year, but varies considerably between years.[5] The river is then joined by various tributaries, but also loses more water due to evaporation. The quantity of water entering Nigeria measured in Yola was estimated at 25 km3/year before the 1980s and at 13.5 km3/year during the 1980s. The most important tributary of the Niger in Nigeria is the Benue River which merges with the river at Lokoja in Nigeria. The total volume of tributaries in Nigeria is six times higher than the inflow into Nigeria, with a flow near the mouth of the river standing at 177.0 km3/year before the 1980s and 147.3 km3/year during the 1980s.[5]

The Niger takes one of the most unusual routes of any major river, a boomerang shape that baffled European geographers for two millennia. Its source is just 240 km (150 mi) inland from the Atlantic Ocean, but the river runs away from the sea into the Sahara Desert, then takes a sharp right turn near the ancient city of Timbuktu (Tombouctou) and heads southeast to the Gulf of Guinea.

This strange geography apparently came about because the Niger River is two ancient rivers joined together. The upper Niger, from the source past the trading city of Timbuktu to the bend in the current river, once emptied into a now-gone lake, while the lower Niger started in hills near that lake and flowed south into the Gulf of Guinea. As the Sahara dried up in 4000–1000 BC, the two rivers altered their courses and hooked up.[citation needed] This explanation is generally accepted, although some geographers disagree.[citation needed]

The northern part of the river, known as the Niger bend, is an important area because it is the closest major river and source of water to that part of the Sahara desert. This made it the focal point of trade across the western Sahara, and the centre of the Sahelian kingdoms of Mali and Gao.

The surrounding Niger River Basin is one of the distinct physiographic sections of the Sudan province, which in turn is part of the larger African massive physiographic division.