Being on the southern fringe of the Sahara Desert in north-central Africa, Lake Chad extends over the territories of four countries: Chad, Niger, Nigeria and Cameroon. Owing to the supply of river water from the highlands to the south, it remains a freshwater lake under the prevailing arid climate. Apparently no river flows out from the lake, though some water is said to percolate along the dry bed of the Gazal River to feed the oases of the Bodele Depression about 40 km to the northeast.

The water level is variable as it is influenced by the rainfall fluctuation both seasonally and annually. The lake size was five times its present size (ca. 20,000 km2) several thousand year ago, while the drought years in the 1970's made the northern half of the lake (Northern Basin) completely dry and turned the Southern Basin into a densely vegetated area with scattered swamps and open pools.

L. Chad is very shallow even in normal years, averaging 1.5 m in depth. It is fringed by a zone of swampy vegetation dominated by reeds (Phragmites spp.), papyrus (Cyperus papyrus) and cattail (Typha australis). These water plants often form dense thickets or floating mats even in the centre of the lake. Local inhabitants use the stems of papyrus as material for canoe making. There are many small islands formed by the invasion of moving sand dunes near the northeastern coast; some of them are inhabited and utilized as bases for fishing. Besides the products of agriculture, livestock grazing and fishery, the drainage basin of L. Chad is known for its yield of natural soda, an activity that contributes to keeping the lake water fresh (Q2).