Lake Chad, which belongs to the countries of Chad, Cameroon, Nigeria, and Niger, is a sedimentary basin that is controlled by climate and rainfall. The lake is divided into two basins—the south basin fed by the Chari River and the north basin fed by the Komadougou River. The south basin, with its delta along the southern shore, has a distinct advantage in that the Sahel (a transition zone between the true desert and the grasslands south of the desert) generally receives more precipitation than the region west of Lake Chad that provides recharge water for the north basin. The south basin’s water level has remained relatively constant during the decades of 1980s and 1990s, while the north basin has shown little evidence of standing water since the late 1960s and early 1970s. Extensive sand dunes exist within the northern half of the south basin, but there appears to be vegetation in this area.