Geophysical characteristics

• The Lake Chad basin lies at the Southern edge of the Sahara Desert.
• It is the largest drainage basin in Africa covering 8% of the African continent.
• The basin covers 2.5 million square km.
• Lake Chad is shared by Chad, Cameroon, Niger, and Nigeria but the basin extends to Algeria, Central African Republic, and Libya.
• Lake Chad has a very unstable water balance that changes drastically due climatic factors associated with the Sahara Desert and the demands for water use for irrigation, watering animals, dams, and other uses in an arid setting.
Read More
It was originally the largest lake in Africa at that time known as Mega Chad that covered 300,000-400,000km2.
It shrunk by 95 % between 1963 and 1998.
By 1983 it was covering 10,000 - 25,000 km2 but by 2000 it had shrunk to <1,500 km2 and is estimated to be 1,350 km2
The lake is divided in the southern and northern basins by a sand bar which become more conspicuous during when the lake level falls due to drought.
It has a shore line length of 650 km, an average depth of 1.5 m, maximum depth of 11 m, and a volume of 72 km3.
The main inflow is the Chari River. Other rivers include Bahr el Ghazal, Serbeouel, El Bied, Yedseram, and Komadugu-Yobe most of which flow into the lake from the south.
It is an endorheic lake with no outflow.
The LCB has low rainfall of 200mm in the north and 500mm in the south (Beadle 1982).
Most of the water (95%) is gained through inflow from River Chari and 90% is lost through evaporation.
The economic activities in the LCB include: Agriculture, Fishing, Pastoralism, Manufacturing, Mining, and Oil exploration and exploitation.
Changes in water availability is accompanied by migrations to find suitable agriculture, fishing and grazing grounds.
The high dependence on scarce water resources have resulted into conflicts over water access rights for different economic activities especially between farmers and herders for access to water for crop irrigation and watering animals.
There have also been some armed conflicts in the region.
Development efforts in the LCB have concentrated on addressing the problems facing the environment and people of the region amidst scarce water resources.

Demographic characteristics

• The human population growth rate in the basin high (2.5 and 3.0%) with most of it in the southern basin.
• The basin had 37.2 in 2003 million with the majority (59%) in the Nigerian part of the basin.
• The countries of the LCB are among the 23 poorest countries in the world with >60% of the people poor.
• Access to potable water was in 2000 was much lower in rural areas (31.3%) compared to urban areas (86,2 %).

Fishes and fisheries

• The LCB has 179 fish species most of which are shared with the Niger, Nile, and Congo River sub-basins.
• There are 25-30 endemic fish species in the LCB but only one, Brycinus dageti is exclusively found in the lake with the others shared with adjacent sub-basins (Beadle 1981).
• Fish species diversity has declined rapidly with 41% of the species in the Nigerian part of the basin disappearing in one decade.
• The decline in biodiversity has been attributed to loss of critical habitats especially reduction lake level and wetland vegetation.
• The open waters of the lake are normally replaced by swamp species as water levels fall and open water area is reduced due to drought.
Read More
Annual fishery yield from Lake Chad has fluctuated from 10,000t in 1960 to 200,000t by 1974 and to 10,000–20,000t 1987.
The increase in fishing effort was attributed to introduction of nylon gillnets and expansion of markets.
There are about 150,000 fishermen on the lake.
The most recent estimates suggest that annual fishery yield is about 100 000 tons, valued at about USD 200 Million.
The fluctuations in fish stocks have been attributed the fall in lake levels, excessive fishing effort, and increased use of small mesh gillnets which capture immature fish.
Alteration in the fish habitat from an open water to a predominantly marshy environment and changes in lake levels has been accompanied by changes in dominance of fish species with species like Heterotis niloticus, Alestes spp and Gymnarcus niloticus becoming scarce and Tilapia (Oreochromis spp) more abundant.
The sizes of the most important commercial fishes the characin, Alestes baremoze and the Nile perch, Lates niloticus have declined.

The lake habitat

• The lake habitat is influenced by the desert in the north and the wetter south and from where most of the rivers flow into the lake.
• There are wide range in annual temperature over the lake by as high as 10oC.
• The lake is polymictic and well oxygenated to the bottom including macrophyte zones due to strong winds.
• Secchi disk reading in 1960s were 50-100 cm.
• The nutrients concentration is influenced by annual flooding from June to December which affects turbidity, algal, invertebrate and fisheries production.
Read More
Conductivity varies from 90 µmhos in the south where most rivers enter the lake to 600 µmhos in the extreme desert north where there is virtually no river entering the lake (Hopson 1972).
The lake is highly alkaline with pH of 8.5
The phytoplankton community of is dominated by Blue Green algae especially Microcystis and Aphanocapsa but Diatoms especially Melosira spp increase with floods probably due to nutrient replenishment.
The zooplankton community is dominated by Cladocerans, Copepodes, and Rotifers. Both phytoplankton and zooplankton changes with lake levels.
The bottom type of the lake varies considerably and include, muddy, clay, sandy, peat areas. These, in addition to seasonal factors, affect distribution of benthic invertebrates.
The Chari-Logone river system which supplies most of the water to the lake has been invaded by Water hyacinth and the lake itself by Typha and Water hyacinth.
Proliferation of invasive weeds mainly occurs when water levels in floodplains and river channels fall.
The Sahel region has experienced the most substantial and sustained decline in rainfall recorded anywhere in the world since climate change intensified. This has resulted in changes in hydrological regimes which drives environmental changes, production, and livelihoods in the LCB.

Basin factors

• People in the LCB depend on Agriculture, Livestock, and Fisheries for their livelihoods but these are highly affected by scarce water resources. Crops have to be irrigated, pastoralist migrate to the wetter regions in search of pasture and water, and fishers have to respond to changing fisheries regimes it time and space.
• Timber is the primary source of fuel wood and construction material and timber resources in the LCB have been over harvested which exposed the soil and enhances erosion.
• Overgrazing also cause reduced vegetation covers.
• The whole of Lake Chad is a wetland and has been designated a Ramsar site.
• It is the second largest wetland in West Africa and one of the most important in Africa.
Read More
Lake Chad is more of a flood plain because less than half of the lake is covered by open water throughout the year with the rest by marsh vegetation.
The lake has, due to reduced water supply changed from an open water to a marshy environment, and about 50% wetland vegetation has disappeared.
Dams have been constructed to support large scale rice and cotton production and small hydropower dams but this reduces and affects the amount of water that reaches the lake and affects lake levels.
There are five main cities in the Chad basin including Kano and Maiduguri in Nigeria, Maroua in Cameroon, N'Djamena in Chad and Diffa in Niger but these are not close to lake shore or inflowing rivers. Consequently, urbanization has limited impact on the lake.
There is some oil and gas exploration and exploitation and some minerals such as gold are exploited in some parts of the LCB. These can cause pollution and provide additional stress to the lake and its resources and needs to be managed.
There are two protected areas along the lake shore (Douguia National Park in Chad and the Lake Chad Sanctuary in Nigeria).
The LCB is also an important bird area with 372 species of birds.
Navigation on the lake is limited by its shallowness and the large fluctuations in the lake depth and open water macrophytes which have made development of navigation infrastructure and navigation on the lake difficult.
agro chemicals and fertilizers used on commercial cotton and rice farms are potential sources of pollution.
Traces of heavy metal pollutants zinc, mercury and magnesium especially from tannery and textile industries have been reported in the region and need monitoring.
There is increasing sedimentation of the rivers and the lake due to unsustainable farming practices on marginal lands. This is has affected the depth of the lake, bottom sediments and associated organisms.
Sedimentation is enhanced by decreases in channel flows due to loss in ability of the rivers to flush out their channels at the onset on the rainy season.

Governance