Waterways and Seasons
The national water net is essentially composed of two rivers: the Chari, 1,200 km long and emanates from the Central African territory; the Logone, 1,000 km springs in Cameroun. The two rivers form a confluence near the capital N’Djamena, and travel together for about 125 km before they cockle in the Lake Chad. Apart from Lake Chad, which is the principal lake, there is also the Fitri, Iro, Lere, Tikem, and the two Ounianga lakes. Oasis are scattered in the desert zone in the north.
On the other hand, Lake Chad receives water from other streams, of which the most important ones are: Halha, Bahr-El-Gazal, Bahr-Aouk, Malir-Keita, Mandoul, Pende. But these rivers and other streams are not capable to stop the vaporescence and reduction of Lake Chad, which was many centuries ago called “the paleo-Chadian sea”; millions of years ago this continental sea came from Bardai, but in just a matter of a few centuries it reduced, measuring only 25,000 square km in the 1960s. Today the ground-water table of Lake Chad is of merely 3,000 square km. However, it still constitutes Chad’s main water reservoir. Its volume is estimated to be 40 cubic meters on average, which represents 80 per cent of the waters of the Chari and the Logone.
The beginning of precipitation is announced by a humid wind coming from the south-west from April/May in the south, and May/June in N’Djamena in the north.
Rain season: in the south from May to October, in the centre from June to October, variable in the north from June to September.
Dry and cold season:
from October/November until February, sand wind (harmattan) blows in the north-east. The annual average temperature in the whole country is 20 degrees, with maximums between 30 and 35 degrees during the warm season, and minimums between 20 and 23 degrees. In N’Djamena (Sahel zone), the seasons are as following:
July to September: occasional thunderstorms and rain, followed by a slight decrease in temperature varying between 21 and 35 degrees; the level of humidity is increased.
October to mid-November: warm season without rain, but relatively humid
Mid-November to mid-March:
Dry season more or less cold, with very cool evenings and nights, in which the temperature declines to 8 degrees.
February and March: sand wind period (harmattan)
End of March to June: very hot and dry season: the temperature decreases only rarely less than 35 degrees, and during the day she can rise to 46 degrees in the shadow.