(a) On an outline map of Nigeria, locate and name (i) one inland drainage basin (ii) three rivers that flow into the basin (iii) the Bight of Benin and Bigh...

Answer Details

As shown on the map above, the required inland drainage basin is the Lake Chad Basin, located in the north-eastern part of Nigeria.

(a) Locations and names on the map

• Inland drainage basin: Lake Chad Basin, in north-eastern Nigeria.
• Rivers flowing into the basin: Rivers Hadejia, Komadugu Yobe and Yedseram. Other acceptable examples include River Ngadda.
• Bight of Benin: on the south-western section of Nigeria’s Atlantic coast, west of the Niger Delta.
• Bight of Bonny: on the south-eastern section of Nigeria’s Atlantic coast, around the Niger Delta area.
• Idanre Hills: in south-western Nigeria, in Ondo State.
• Oban Hills: in south-eastern Nigeria, mainly in Cross River State near the Cameroon border.
• Biu Plateau: in north-eastern Nigeria, in Borno State.

(b) Reasons for the shallowness of the rivers and Lake Chad

• The Lake Chad Basin is an inland or closed drainage basin. Rivers flow into Lake Chad, but there is no major river flowing out of it to carry away water and deposited materials.
• Rivers entering the lake deposit large quantities of silt, sand, clay and other weathered materials. These materials gradually fill the river channels and the lake bed.
• The area has a hot, semi-arid climate; therefore, there is very high evaporation from the rivers and lake surface, reducing the volume and depth of water.
• Rainfall is generally low and seasonal, so many of the rivers have reduced flow during the dry season and cannot maintain deep channels.
• The land is generally flat and gently sloping, causing rivers to flow slowly and deposit rather than remove sediments.

(c) Benefits of Lake Chad

• Fishing: The lake provides fish and supports the livelihood of fishermen, fish traders and fish processors.
• Irrigation: Its water is used to irrigate crops, especially during the dry season.
• Water supply: The lake and its tributaries provide water for domestic uses, livestock watering and some industrial activities.
• Transport and trade: Parts of the lake and connecting waterways can be used for the movement of people, goods and local trade.
• Grazing and farming: Receding water leaves fertile alluvial soils which support floodplain farming and dry-season grazing.
• Employment: Fishing, farming, boat transport, trading and reed harvesting provide employment for people living around the lake.