Desert Environments of Republic of Chad - Combating Desertification in Asia, Africa and the Middle East - page 166

of the year, it receives 350 mm or more of rain, mostly during July and August.
A carpet of green springs from the desert during this brief wet season, attracting
herders from throughout the region who come to pasture their cattle and camels.
Because very few wells and springs have water throughout the year, the herders
leave with the end of the rains, turning over the land to the antelopes, gazelles, and
ostriches that can survive with little surface water.

3.2 Sahelian Region

The semiarid sahelian zone, or Sahel, forms a belt about 500 km wide that runs
from Lac and Chari-Baguirmi prefectures eastward through Guera, Ouaddaı, and
northern Salamat prefectures to the Sudanese frontier. The climate in this transition
zone between the desert and the southern soudanian zone is divided into a rainy
season (from June to early September) and a dry period (from October to May).
In the northern Sahel, thorny shrubs and acacia trees grow wild, while date palms,
cereals, and garden crops are raised in scattered oases. Outside these settlements,
nomads tend their flocks during the rainy season, moving southward as forage and
surface water disappear with the onset of the dry part of the year. The central
Sahel is characterized by drought-resistant grasses, shrubs and low trees. Rainfall is
more abundant there than in the Saharan region. For example, N'Djamena records
a maximum annual average rainfall of 580 mm, while Ouaddaı Prefecture receives
just a bit less. During the hot season, in April and May, maximum temperatures
frequently rise above 40 ı C. In the southern part of the Sahel, rainfall is sufficient
to permit crop production on unirrigated land, and millet and sorghum are grown.
Agriculture is also common in the marshlands east of Lake Chad and near swamps
or wells. Many farmers in the region combine subsistence agriculture with the
raising of cattle, sheep, goats, and poultry.

3.3 Soudanian Region

The humid soudanian zone includes the southern prefectures of Mayo-Kebbi,
Tandjile, Logone Occidental, Logone Oriental, Moyen-Chari, and southern Salamat.
Between April and October, the rainy season brings between 750 and 1,250 mm
of precipitation. Temperatures are high throughout the year. Daytime readings in
Moundou, the major city in the southwest, range from 27 ı C in the middle of the
cool season in January to about 40 ı C in the hot months of March, April, and May.
The soudanian region is predominantly savanna, or plains covered with a mixture
of tropical or subtropical grasses and woodlands. The growth is lush during the
rainy season but turns brown and dormant during the 5-month dry season between
November and March. Over a large part of the region, however, natural vegetation
has yielded to cropland.