Niger River

Physical Geography

The Niger River located in the heart of West Africa flows from its source in the Guinea Highlands along its 4,180 km course, through nine countries, to its mouth at the Niger delta where the river waters flow into the Gulf of Guinea, Atlantic Ocean. While the Niger River iself gains its name from the Greeks along the course of the river it is known by many names including Joliba in the upper course, meaning “Great River”, Isa Eghirren and Mayo Balleo along the middle course and Quorra in the lower course. The geographical change throughout this basin is vast with the total catchment area of the Niger River being 2.1177 million km², therefore below the Niger river and its basin will be analysed to provide an overview of the changes seen from the upper course through to the middle and lower courses before reaching the Niger delta where the River meets the Atlantic.

Formation/Geology

The Niger river finds its source in the Guinea Highlands only 240 km away from the Atlantic Ocean, at this point known as the Tembi flowing from a revine 850 m above sea level. The river flows north from the Guinea Highlands for the initial 160 km of its course before moving northeasterly where it is met by the key upper course tributaries before entering Mali near its capital of Bamako. At this point in the course of the Niger river the system moves into the middle course of the river with the Sotuba Hydroelectric Dam, located in Bamako, acting as the final marker within the Upper course of the Niger river.

As the Niger river continues into its middle course, the river loses 300 m of elevation in approximately 60 km as a result of tectonic plate movement. A major portion of this initial stretch of the middle course has historically been whitewater rapids however, they have now disappeared as a result of the Markala Dam that is located approximately 240 km downstream from this stretch of the river. The Niger river once again changes course flowing in an east-northeasterly direction where it flows almost unimpeded for 1,600 km. Once the Niger river reaches Mopti, Mali it is met by one of its largest tributaries the Bani river before entering a region that is known as the internal delta of the Niger, in a region that is dominated by seasonal lakes, creeks and backwaters. This intertwined section of the river comes to an end at Timbuktu where the Niger once again changes direction flowing east. After the river flows east for 400 km the Niger reaches a geological obstruction that the Niger has eroded away to form a gorge that is approximately 2 km long with an average width and depth of 240 m and 30 m respectively. Creating a short stretch of the Niger that cannot be navigated at low water levels. Following this gorge the river begins to flow southeast, increasing in width at this point to between 5 and 10 km wide. Following this point the Niger flows through the southern edge of the Sahara desert, the river then continues along its course flowing to Jebba in Nigeria where the river enters into its lower course.

Once in its lower course the Niger is joined by a tributary that provides a quarter of the annual river discharge, the Kaduna river, shortly downstream from Jebba. Following this confluence the Niger river begins to move south, just above Lokoja Nigeria where another key tributary confluences with the Niger, the Benue, which then doubles the discharge of the Niger. At this point the Niger river is approximately 1 km wide with the Benue being even wider leading to a section of the river with the river's width exceeding 3 km. The Niger then flows into a restricted valley with steep sandstone cliffs spanning 45 m in height with this valley narrowing as the Niger flows through a fault within the sandstone geology of the region. The Niger then emerges at Aboh separating into multiple courses before reaching the Gulf of Guinea forming the Niger delta, Africa’s largest delta.

Climate

Temperatures in the basin range greatly however it can be noted that mean monthly temperatures across the basin range from 21°C to 32°C with the highest and lowest temperatures being registered in the middle course of the river. Mean annual precipitation ranges from 4,100 mm in the delta region to 250 mm in the upper course recorded in Timbuktu while the middle course of the Niger is much drier as outlined with the river flowing along the southern edge of the Sahara desert. As a result of anthropogenic climate change the basin has seen many changes in climatic trends with projected increases in temperature set to further exacerbate an area that is known for droughts. Overall the climate of the Niger basin is characterised by the high level of variability that is seen across the catchment as well as the prevalence of extreme climate events such as flooding and droughts that greatly impact regions of the Niger river basin.

Human Geography

Humans have been situated in this area since the dawn of mankind living within the natural environment, however, modern advances in technology and urbanisation across the basin have led to many changes in the natural environment that is situated in the region. This can be seen with the construction of dams along the course of the Niger negatively impacting the sediment transport regime of the river. The implications of the anthropogenic actions and hard engineering strategies throughout the basin can be seen with the destruction of many habitats both aquatic and terrestrial, reduction of river flow, increased sources of pollution stemming from industry and sewage as well as intensive agricultural activity requiring large water resources.

Dredging

Major governmental actions have been taken throughout the basin for dredging efforts along the course of the Niger river this was seen with the Nigerian government approving dredging efforts for several hundred kilometers of the river to remove silt. These efforts are to improve transportation links using the Niger river itself, however, this will greatly damage many fluvial habitats of both flora and fauna leading to the loss of biodiversity in the catchment. This was undertaken by the Nigerian government to make the Niger river navigable for the entire year inturn leading to nigeria becoming one of the most industrialised nations in the world. There have been many opponents to this measure being undertaken with the threat that is posed to both the natural environment and those that live along the banks of the Niger.

Pollution

The Niger delta is home to Africa’s largest oil production with the abstraction of oil and petroleum products, with major petroleum operations occurring in the region since the 1950s, as such the region is also one of the most heavily polluted regions in the world. In a 25 year span from 1976 to 2001 there were approximately 7,000 incidents that involved oil spills, with an annual average spillage of 240,000 barrels of crude oil, where oil reclamation efforts were unsuccessful with extremely negative environmental impacts associated with them (Amnesty International, 2009). These spillages have major environmental implications with the contamination of both surface water & groundwater, air quality as well as the bioaccumulation of hydrocarbons within crops grown in the region. As such there is a large threat to the health of the inhabitants of the delta with little access to uncontaminated water and food sourced within the delta as well as a potential for the reduction of fertility in the basin and an increase in cancer due to the oil contamination across the delta.

Climate Change

Climate change presents a major threat to the Niger basin impacting the security of water resources, humans and their livelihoods having the potential to be one of the major conflicts over potable water in the coming decades. Anthropogenic climate change will lead to an increase in the extreme events seen across the Niger basin with the potential for not only more frequent and worse droughts but also flood events that would impact lives, livelihoods and the productivity throughout the basin. With the greatest potential for damage occurring in rural communities where there is a heavier reliance on the river to sustain practices such as farming.

Projected increases in temperature would also lead to a higher required intake of water for both humans and other biota across the basin further straining the water resources in this region. There is potential for the movement of the desert boundary that is situated within the basin as a result of anthropogenic climate change, with desertification leading to loss of water resources as well as major environmental and ecological change across the basin.