(a) On an outline map of Nigeria, locate and name: (i) the Niger-Benue trough; (ii) Rivers Niger, Benue, Gongola and Donga; (iii) one confluence town in the...

(a) Location map of Nigeria

Key locations: The Niger-Benue trough is the broad Y-shaped lowland occupied by the valleys and floodplains of Rivers Niger and Benue. River Niger enters Nigeria from the north-west and flows south-eastwards to Lokoja. River Benue flows westwards from the east to join the Niger at Lokoja. River Gongola is a northern tributary of the Benue, while River Donga joins the Benue from the south-east. Lokoja is the confluence town.

(b) Physical characteristics of the Niger-Benue trough

The Niger-Benue trough is a broad, Y-shaped, low-lying region extending across central Nigeria. It consists mainly of the valleys of Rivers Niger and Benue and the land around their confluence at Lokoja. Much of the trough is below about 300 m above sea level, although it is bordered in places by higher uplands and plateaux, including the Jos Plateau and the eastern highlands.

Its relief is generally flat to gently undulating. Wide floodplains, swamps and fadama occur along the rivers, especially where seasonal flooding deposits sand, silt and clay. Some areas have low, flat-topped sedimentary hills separated by river valleys.

The area is drained chiefly by Rivers Niger and Benue. Important tributaries include the Gongola, Donga and Kaduna rivers. The Niger and Benue meet at Lokoja and thereafter flow southwards as the River Niger. During the rainy season, the rivers overflow parts of their floodplains.

The climate is tropical continental, with a distinct wet season and dry season. Rainfall is generally over 120 cm annually in many parts of the trough, and relative humidity is high during the wet season. Natural vegetation is predominantly Guinea savanna, made up of tall grasses and scattered deciduous trees. Gallery forest occurs along river banks and in wetter floodplain areas.

The trough is underlain mainly by sedimentary rocks. Its floodplains have fertile alluvial and hydromorphic soils, while deposits of limestone, clay and salt occur in some localities.

(c) Relationship between physical characteristics and economic activities

1. The fertile alluvial soils and seasonal floodplains support farming, particularly rice, sugar cane, vegetables, yams, maize and soyabeans. Swampy fadama areas are especially suitable for rice cultivation and dry-season irrigation.
2. The Niger, Benue and their tributaries provide water for irrigation and support fishing. They also serve as inland waterways for the movement of people and goods.
3. The large rivers and their flow permit hydro-electric power generation and encourage such activities as boat building. Dams and river projects also provide water for irrigation.
4. Sedimentary mineral deposits support industries: limestone favours cement manufacture, clay promotes pottery and brick-making, while salt-bearing deposits encourage salt extraction.