Lake Chad

Lake Chad, French Lac Tchad The Niger and Sénégal river basins and the Lake Chad basin and their drainage networks.Encyclopædia Britannica, Inc.freshwater lake located in the Sahelian zone of west-central Africa at the conjunction of Chad, Cameroon, Nigeria, and Niger. It is situated in an interior basin formerly occupied by a much larger ancient sea that is sometimes called Mega-Chad. Historically, Lake Chad has ranked among the largest lakes in Africa, though its surface area varies greatly by season, as well as from year to year. When the surface of the lake is approximately 920 feet (280 metres) above sea level, the area is about 6,875 square miles (17,800 square km); in the early 21st century, however, the area was typically about 580 square miles (1,500 square km). The hydrologic contributions and biological diversity of Lake Chad are important regional assets. The region is noteworthy for important archaeological discoveries, its role in trans-Saharan trade, and its association with historic African kingdoms.

Physical features

Geology and physiography




Precipitation levels are greatest from July to September. Annual precipitation averages 22 inches (560 mm) at the southern margin of Lake Chad and about 10 inches (250 mm) at the northern margin. Variability during the year is high and increases from south to north; variability from year to year is also high, and droughts are frequent. Temperatures during the wet season are moderate, with highs in the low 90s F (low 30s C). In October and November, during the transition to the dry season, daily highs rise above 90 °F (32 °C), and diurnal ranges are almost double those of the wet season. During December and January daytime highs are lower, with nighttime lows sometimes falling to the high 40s F (about 8 °C). April is usually the hottest month of the year, with temperatures occasionally reaching the low 110s F (low 40s C).


Lake Chad is a variable body of water. Its measured surface area typically fluctuates seasonally, peaking in late October or early November, then shrinking by more than half by late April or early May. The lake is dotted with numerous islands, which can coalesce into larger land areas during periods of extremely low surface levels. The volume of the lake reflects local precipitation and the discharge of its catchment area, balanced against losses through evaporation, transpiration, and seepage. The lake is fed chiefly by the Chari (Shari)-Logone river system, which accounts for about four-fifths of the inflow. Of the remaining inflow, most is contributed by the Ebeji (El-Béid) and Yedseram rivers. Losses to evaporation and the transpiration of aquatic plants amount to approximately 100 inches (2,500 mm) each year. It is probable that up to another 10 inches (250 mm) replenish groundwater supplies in the adjacent Manga and Kanem lowlands and pass as underflow through the El-Ghazal.

At times when the lake has a greater surface area, it can be divided into two pools partially separated by a low ridge extending roughly northeast-southwest across the centre of the lake; the ridge was formed during a drought at the beginning of the 20th century, and at times it has completely divided the basins. Typically, depths of 13 to 23 feet (4 to 7 metres) are common in the northwestern pool, and 33-foot (10-metre) depths can occur among the islands along the eastern margin of the pool. Because of sediment deposition by the Chari River, the southeastern pool is generally shallower—10 to 13 feet (3 to 4 metres) deep—but sometimes reaches depths of 36 feet (11 metres) along the archipelago. The gentle slope of the lakeshore allows persistent dry-season winds to locally affect water levels for short periods of time. The salt content of Lake Chad is unusually low for a tropical dryland lake with no outlet. As the waters of the lake evaporate during the dry season, the salt content increases, with the highest values recorded along the northeastern shoreline.

Travelers reported high water levels and overflow into the El-Ghazal during the 13th and 19th centuries. In 1870, for example, Lake Chad covered some 10,800 square miles (28,000 square km). At the turn of the 20th century the lake began to diminish in size, but by the 1920s it had recovered, and in 1956 it again overflowed into the El-Ghazal. During the 1970s and ’80s the amplitude of the lake’s annual variability was the highest recorded in the 20th century, with average levels falling below long-term norms; the surface area was reduced to less than 1,500 square miles (3,900 square km) for a time in the mid-1980s and again in the early 21st century. The corresponding variability in rainfall appears to have been related to the effects of environmental degradation.

Plant life


Animal life


Secretary bird (Sagittarius serpentarius).© Stephen J. Krasemann/Peter Arnold, Inc.African lungfish (Protopterus annectens).Copyright Tom McHugh—Steinhart Aquarium/Photo ResearchersHundreds of species of birds reside permanently or seasonally in the Lake Chad region. Included are prominent terrestrial birds—such as ostriches, secretary birds, Nubian bustards, and ground hornbills—and the water and shore birds for which the region is famous—such as the garganeys, shovelers, fulvous tree ducks, Egyptian geese, pink-backed pelicans, marabou storks, glossy ibises, and African spoonbills. Included among the amphibians and reptiles are Nile crocodiles, rock pythons, and spitting cobras. The Chad basin remains an important fishery, with more than 40 species of commercial importance. Also noteworthy are such ancient species as the lungfish and sailfin.

People and economy

Settlement history

The Chad basin contains the earliest evidence of hominin occupation yet found in western Africa, and it appears that the Lake Chad region has been continuously settled since 500 bce. Among the major archaeological discoveries of the region has been the Sao civilization; it is believed that the modern Kotoko, a fishing people on the Chari near Lake Chad, are descendants of the Sao.



Agriculture and forestry

Subsistence crops include sorghum, corn (maize), African millet, beans, and vegetables. Bottle gourds are grown widely for making utensils. Polders (tracts of lowlands reclaimed from a body of water) near Bol, used to grow cash crops, are based on traditional agricultural practices. Cultivated by the Kanembu and Yedina, the polders are devoted chiefly to wheat.


Livestock and fishing


Fishing, traditionally the most important economic activity for the peoples of the lake, all but ceased during the drought and resumed only in the mid-1990s. Much of the catch is dried, salted, or smoked. Dried Alestes species, known by the name salanga, and pieces of smoked fish called banda are marketed, primarily in Nigeria and Cameroon.


Natron being unloaded along the eastern shore of Lake Chad near Baga Sola, Chad.© Jacques Jangoux/Peter Arnold, Inc.Petroleum reserves have been discovered in Chad and Niger. Natron (hydrated sodium carbonate), found in depressions along the northeastern shore of the lake, has long been economically important. Traditionally, it is excavated in blocks and shipped across the lake, where it enters Nigerian commerce.



Study and exploration

