1. WEEK 3: DRAINAGE OF NIGERIA
CONTENT
Drainage refer to water bodies like rivers and lakes.
RIVERS IN NIGERIA
Most of the country is drained by the Niger, Benue and their tributaries.
River Niger, the largest river in Nigeria ha its source from Guinea highlands in Guinea.
It passes through Mali and Niger Republic to Nigeria.
River Benue has its source from eastern highlands and joins the Niger at Lokoja, because of this, Lokoja is known as a confluence town.
Other rivers take their sources from highlands in Nigeria known as hydrological centres. These centres are:

2. Western Highlands
They have rivers such as Ogun, Osun, and Osse which flow directly into the Atlantic ocean.
2. North-central Highlands
The drainage pattern is clearly centrifugal or radial, with Jos Plateau constituting the central dome.
They have such rivers as Kaduna, Hadejia, Zamfara, Yobe, Gana, Gongola, gboko, Mada and Rima which rise and flow in different directions.
3. Eastern Highlands
They have rivers like Donga, Yedseram, Katsina Ala, Cross river, Taraba and Naado river.
These rivers flow into either lake Chad, river Benue or Atlantic ocean.
4. The Eastern Scarplands
They have rivers like Anambra, Ajalli, Adaba, Mamu and Oji all of which flow into river Niger.
CHARACTERISTICS OF NIGERIA RIVERS
The volume of the rivers changes with season: Volume increases during rainy season and decreases during dry season.
Presence of rapid and cataracts: These rapids and cataracts impede or disturb inland navigation.

3. Presence of debris: Such debris include dead leaves, mud, wood etc.
Short courses with high speed: Most rivers are usually very short and flow rapidly or swiftly e.g. rivers Ogun, Osun and Cross river.
Specific direction of flow: Rivers in the south flow in the north-south direction into the sea while rivers in the north flow in a radial pattern to different directions.
Shallowness: Most rivers are very shallow and full of silt associated with high evaporation and seepage of water into the soil.
The colour changes with season: The rivers have muddy and dirty colour during raining season but remain clear and clean during dry season.
Seasonality: Most rivers flow during rainy season but stop or reduce flowing during the dry season.
USES OR IMPORTANCE OF NIGERIA RIVERS
Medium of transportation: Large rivers like Niger and Benue serve as medium of transportation from one place to another.
Rivers provide water for irrigation especially when they are dammed.
They help to generate hydro-electric power e.g. Kainji, Jebba and shiroro.
Water from rivers is used for various domestic purposes such as cooking, washing and bathing.
Water from rivers is also required by many industries such as textile, brewery and chemical industries.

4. 6. Rivers do provide employment to many people e. g
6. Rivers do provide employment to many people e.g. fisher men, canoe and ship building.
7. Rivers are known to provide food for many in form of fish, prawns, crayfish, crab .e.t.c.
8. Some rivers are centres of tourist attraction and may generate foreign exchange for a nation e.g. Argungu fishing festival in Kebbi state.
9. Some rivers are good sites for the construction of river ports.
10. Formation of flood plains by rivers also provides fertile soil for agricultural activities.
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.
In Nigeria, there are five major river basins.
These are:
(i). The Niger Basin (ii). The Benue Basin (iii). The Chad Basin
(iv). The Cross River Basin (v). The South Atlantic Basin.
The rivers in these basins are grouped into three classes of :
Long rivers with large basin: These rivers flow to the sea across long distances through the land e.g. rivers Niger and Benue.

5. 2. Short rivers with small basin: These rivers also flow to the sea but are very short e.g. rivers Osun, Ogun, Cross river e.t.c.
3. Rivers in basins of inland drainage: These rivers do not reach the sea but rather they flow into lake Chad e.g. rivers Yobe, Hadejia, Yedseram and Gana.
IMPORTANCE OF RIVER BASINS
Good sites for settlements: River basins are depressed lowlands that enable people to settle and build houses.
Suitable land for agriculture: River basins with alluvial plains are fertile lands for agriculture purposes.
Medium of communication: The presence of rivers enables people to transport themselves and their goods from on place to another.
River basins serve as deposits for minerals e.g. petroleum in the Niger Delta area.
Water from rivers in the basins may be used for domestic and industrial purposes.
Rivers in the basins do provide or act as fishing ground for fishermen.
LAKES IN NIGERIA
A lake is a body of water surrounded by land.
The lakes in Nigeria are grouped into two major types.

6. Man-made or artificial lakes
These lakes are constructed by man.
Examples include lake Kainji on river Niger and Shiroro lake on river Kaduna.
2. Natural lakes
These are lakes which exist naturally.
Lake Chad is the only popular example
Lake Chad is also described as an inland drainage because it receives water from many rivers such as Hadejia, Gana, Yobe, Yedseram e.t.c.
In spite of the fact that lake Chad receives water from many rivers, it is very shallow.
REASONS FOR THE SHALLOWNESS OF LAKE CHAD
Nature of the rivers flowing into the lake
The five rivers that supply the lake with water are shallow, flow sluggishly and pass through semi-desert.
Hence most of the water is lost through evaporation and percolation into soil leading to reduced flow of water in the lake.
2). Tapping of some rivers by river Benue
Specific rivers like River Lagone (outside Nigeria) is being tapped by the Benue headstream. This contributes to reduced volume of water.
3). Location of the lake
The lake is essentially located in Sahara desert and thus it experiences high evaporation leading to low volume of water.

7. 4. Underground drainage
Lake Chad is experiencing underground seepage to nearby oasis. Hence, the shallowness of the lake.
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.