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Lake Chad - physical conditions

In last week post I wrote about changing conditions of the Tanganyika Lake. Today, I would like to take a look at the Lake Chad. The Lake is located in between Cameroon, Nigeria, the RCA, Sudan and Chad (Ngatcha et al., 2005), so it’s in the Sahel/Sahara zone of central north Africa (13°N, 14°E) (Sylvestre et al., 2018).
                                                           The Lake Chad (source)

 The lake covers nowadays almost 8% of the continent. This is not as large as the Tanganyika Lake, however with the size 2,5 x 106 km2 the Lake Chad is one of the biggest Lakes of the world (ibid.). The climate zone has a great influence on the amount of water that is naturally "due" to the lake. In case of the Lake Chad it’s the intertropical convergence zone (ITCZ), which oscillates seasonally between about 150 N and 150S, combined with the northern African monsoon system. This leads to a short rainy season from June to October, the rest of the year is dry (ibid.). The southern part of the lake is semiarid and the north is arid (FAO 2018).

“From the 1960s to the 1980s, the area of Lake Chad shrank from 22 000 km2 to about 300 km2” (Gao et al., p. 1, 2011). To explain, find the reasons of this phenomenon, is not that simple. There are theories which explain the decrease by persistent droughts and increased irrigation withdrawals. This theory will be valid in many respects. Nevertheless, this explanation is not quite sufficient. The northern part is completely dried up and the reasons mentioned above are not enough for this event (Gao etal., 2011), as you can see in the image underneath.
 
2010 Lake Chad's basins source




Main water sources are the water inflow through the Chari and Logone rivers (FAO 2018).It’s said that there has been a general decline in rainfalls, and degradation of the vegetation cover in the last four decades. The annual rainfall is nowadays on entire basin 320 mm varying between to less than 100 mm in the northern parts and 1500 mm in the southern parts of the region of Chad. I read that the Sahel zone has experienced the most substantial and sustained decline in rainfall recorded anywhere in the world in the past 30 years (FAO 2018).

 There is much to suggest that global climate change is the reason for the changing conditions, as rising temperatures and a decline in precipitation can be observed worldwide, for example at Lake Tanganyika. I would like to see in the next weeks what kind of effects can be observed, based on the changing physical conditions at Lake Chad.

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