Lake Chad the Yobe River in Nigeria/Niger. Despite high levels of evaporation, the lake is fresh water. Over half of the lake's area is taken up by its many small islands (including the Bogomerom archipelago), reedbeds and mud banks, and a belt of swampland across the middle divides the northern and southern halves. The shorelines are largely composed of marshes. Because Lake Chad is very shallow—only at its deepest—its area is particularly sensitive to small changes in average depth, and consequently it also shows seasonal fluctuations in size. Lake Chad has no apparent outlet, but its waters percolate into the Soro and
Far North Region, Cameroon the Mandara Mountains. The Mayo Kébi, Mayo Louti, and their tributaries form part of the Niger River basin. The Louti rises in the Mandaras, passing and swelling the Kébi in the North Province. The Kébi rises south of Yagoua and flows into western Chad. The province's other rivers are part of the Chad Basin. The El Beid River flows northwest from the Kalamalou National Park and forms the northernmost stretch of the border between Cameroon and Nigeria. The Mayo Tsanaga rises south and west of the El Béïd's source and moves eastward at the north of the Diamaré Depression. The