WEEK 3: DRAINAGE OF NIGERIA CONTENT Drainage refer to water bodies like rivers and lakes. RIVERS IN NIGERIA The major rivers in Nigeria are Rivers Niger and Benue and each has its own tributaries. The longest and largest river in Nigeria is river Niger which has its source from Guinea highland. River Niger passes through Mali and Niger Republic to Nigeria. River Benue is the second largest river in Nigeria with its source from Cameroun highland and meets river Niger at Lokoja. The following are mountains from where rivers in Nigeria take their sources:

1. North-central Highlands The drainage pattern here is radial. Rivers here include Kaduna, Hadejia, Zamfara, Yobe, Gana, Gongola, gboko, Mada and Rima Rivers in north central highlands flow in different directions. 2. Eastern Highlands Rivers found in this area include Donga, Yedseram, Katsina Ala, Cross river, Taraba and Naado river. 3. The Eastern Scarplands We can find rivers such as Anambra, Ajalli, Adaba, Mamu and Oji here. 4. Western Highlands They have rivers such as Ogun, Osun, and Osse which flow directly into the Atlantic ocean CHARACTERISTICS OF NIGERIA RIVERS Seasonality. Low volume during dry season and high volume during rainy season. Many rivers especially small ones are shallow e.g. river Asejire There are presence of rapids and cataracts which obstruct inland navigation e.g. river Niger Rivers in Nigeria flow in specific direction. The colour of rivers in Nigeria changes with season. Many rivers in Nigeria have short courses but they flow with high speed.

Rivers in Nigeria are shallow and that is why they are not suitable for inland navigation. USES OR IMPORTANCE OF NIGERIA RIVERS Large rivers like Niger and Benue are used for transportation Rivers provide water for irrigation especially when they are dammed. Rivers are used for domestic purposes such as drinking, washing and bathing. Rivers are used for industrial activities e.g bottling companies and breweries. Rivers are used to generate Hydro-electric power e.g. Jebba, Kainji and Shiroro. Many rivers are used for irrigation especially in the northern part of Nigeria. Rivers are used for tourism e.g. Argungu fishing festival in Kebbi state Provision of employment. e.g. fishing. They serve as sources of food e.g. fishes and prawns. They are used for recreational purposes e.g. yatching.

6. RIVER BASIN A river basin is an area where a river or rivers flow through . Such area are at times demarcated for the purpose of developmental planning. River basin is also known as catchment area. River basins in Nigeria include. (i). Sokoto Rima basin (ii). Lake Chad basin (iii). Upper Benue basin (iv). The Cross River Basin (v). Niger Delta basin (vi). Ogun Osun basin (vii). Lower Benue basin (viii). The south atlantic basin. The rivers in these basins are grouped into three classes of : Long rivers with large basin e.g. rivers Niger and Benue 2. Short rivers with small basin e.g. rivers Osun, Ogun, Cross river e.t.c. 3. Rivers in basins of inland drainage. Examples include rivers Yobe, Hadejia, Yedseram and Gana. These river flow into lake Chad.

IMPORTANCE OF RIVER BASINS Settlements. Flood plains in river basins are used for agriculture Low land areas in river basins are used for communication. Some river basins have minerals e.g. petroleum in Niger Delta area Rivers in the basins do provide or act as fishing ground for fishermen. NB: All the importance of rivers also fit into importance of river basins. LAKES IN NIGERIA A lake is a body of water surrounded by land. There are two types of lakes viz: Man-made or artificial lakes These lakes are constructed by man Examples include: Kainji, Jebba and Shororo 2. Natural lakes Major example is lake Chad. Lake Chad is an inland drainage lake because it receives water from rivers like Hadejia, Gana and Yobe but it does not give out water. Although Lake Chad receives water from many sources, the lake is still shallow.

REASONS FOR THE SHALLOWNESS OF LAKE CHAD 1. Nature of the rivers flowing into the lake 2). Tapping of some rivers by river Benue 3). Location of the lake 4. Underground seepage

ASSIGNMENT On the outline map of Nigeria, name and locate: River Niger River Benue River Kaduna River Cross River Osun River Osse River Gongola River Sokoto Lake Chad Kainji dam Shiroro dam Jebba dam NB: This assignment must follow the note on drainage of Nigeria.