Apart from a few more or less permanent pools and seasonal water courses, Niger's main hydrographic network consists of one major river, the Niger, whose eccentric position prevents it from sewing the country as a whole, and a smaller river, the Komadougou Yobé, likewise eccentric.
The River Niger:
The Niger crosses the country over a distance of 340 miles. It is strengthened by several small affluents flowing its right bank, all with a marked Sahelian character; they almost entirely dry up between December and June or July, but flow very strongly in the rainy season (June-September). Moving downstream, are the Goroual, the Dargol, the Sirba, the Diamangou, the Tapoa, and the Mekrou.
Inside the country, the River flows for 125 miles in a bed of crystalline rocks, which causes it to scatter a multitude of small islands in its wake (between Ayerou and Gotheye). Then, in the Boubon region, its banks become steep and rocky, to level out as the river flows towards Niamey, the capital. Downstream from Niamey, there are few alluvial basins, overlooked by quaternary terraces between Kollo and Say. Thereafter, the river's path becomes difficult, forcing it to twist and meander through a hairpin course. The best-known loop of the river is the W National Park, an extensive zone rich in vegetation and wildlife.
The Kamdougou Yobe:
This thousand-km long river marks the boundary between Niger and Nigeria over a distance of 90 miles. It rises from Nigeria and flows into Niger through the Maïne-Soroa region, and then eastwards into Lake Chad. The river has a strong but erratic flow. Its banks are low-lying and rich in alluvium.
Lake Chad:
The Niger part of Lake Chad covers some 1,170 square miles. The lake itself is the vestige of an ancient quaternary sea, at an altitude of 915 feet and today at no point more than 13 feet deep. Islands proliferate in the lake and the evaporation rate is extremely high. 98% of its water supply comes from the Chari River and from rainfall. High water levels occur in December-January, and the lowest levels in June-July.
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