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. L. Chad is very shallow even in normal years, averaging 1.5 m in depth. 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.
Jun Jul Aug Sep Oct Nov Dec Ann. 2 8-year mean. T.incisus circusi, Mesocyclops leuckarti. Archipelago North Basin Open water Archipelago Phytoplankton 0.09 4. Main types of woody vegetation Savannah, mountain and accacia, forests especially on the watersheds of main river basins.