Source and upper course
The Niger rises in the Fouta Djallon highlands of southeastern Guinea, at an elevation of roughly 850 m and barely 240 km from the Atlantic coast, but instead of running directly to the sea it curves inland toward the Sahara before bending back south and east through Mali, Niger, and Benin on its way to Nigeria S1S2. Multiple geographic references converge on a total length of about 4,180 km (2,600 mi), making it the third-longest river in Africa after the Nile and the Congo, and give its drainage basin as roughly 2,117,700 km², spread across ten West and Central African countries S1S2. For most of its middle course through Mali and Niger the river crosses semi-arid terrain, and in June 1985 it dried up entirely at Niamey for the first time in recorded history, an event geographers cite as an early signal of the river's sensitivity to Sahelian rainfall variability S1
Entry into Nigeria and Kainji Dam
The Niger enters Nigeria from the northwest and flows south through Kebbi and Niger states, where it is impounded behind Kainji Dam, completed in 1968 after four years of construction that used more than 250,000 tonnes of cement and 25,000 tonnes of steel S3S4. Kainji Lake, the reservoir this created, stretches roughly 135 km upstream and up to 30 km wide, covering about 1,300 km² and ranking as Nigeria's largest artificial lake S4. The dam was designed for 960 MW of generating capacity, but only 8 of its planned 12 turbines were ever installed, leaving operating capacity at around 760 MW; alongside power generation, the dam improves river navigation upstream to Yelwa in Kebbi State, regulates flow down to the Kaduna River confluence, and supplies water for irrigation and fishing S4. From Kainji the river continues south through Niger and Kwara states, past a second dam and reservoir at Jebba, before reaching Kogi State S1S5
The confluence at Lokoja
At Lokoja, in Kogi State, the Niger is joined by its principal tributary, the river benue, flowing in from the northeast; the merged waters continue south as the Lower Niger S3S5. This confluence has long given Lokoja outsized strategic and commercial importance, and the Nigeria Hydrological Services Agency treats water levels recorded there as a key indicator for flood risk downstream, issuing advisories when both the Niger and Benue approach peak levels together S5. A 2026 advisory from the agency named Kebbi, Niger, Kwara, Kogi, Anambra, Delta, and Bayelsa as the states most exposed to flooding along the river's Nigerian course, after high flows in the middle Niger basin in the Republic of Niger advanced into the Lower Niger while Kainji and Jebba dams were both spilling water downstream S5. Below Lokoja the Anambra River, entering from the east, is the most significant tributary the Niger receives before reaching the coast S5
The Niger Delta
South of the confluence the river fans into the Niger Delta, described in geographic references as the largest delta in Africa and rich in mangrove forest, including the largest remaining tract of mangrove on the continent S1. The wider delta wetland spans more than 100,000 km² across several southern Nigerian states and sits atop reserves that make hydrocarbons roughly three-quarters of Nigeria's national income and about 90% of its foreign-exchange earnings S1. That same delta has lost mangrove cover steadily: satellite-based tracking put coverage at 10,515 km² in 2010, falling to 8,240 km² by 2020, a decline attributed chiefly to more than 6,000 recorded oil spills over the preceding decade, alongside logging and invasive nipa palm S6. The Ogoni people of the delta, who rely on its mangroves and creeks for fishing and other livelihoods, have documented decades of oil contamination in Ogoniland; since 2018 a community-led restoration project has planted some 2.6 million mangrove seedlings, with survival rates of 80–96% depending on the site, aiming for 5 million trees within five years S6
Exploration and historical significance
Europeans took more than three decades to establish the Niger's basic geography. Mungo Park, a Scottish surgeon, reached the river at Ségou in July 1796 and settled the long-disputed question of which direction it flowed, but he was unable to determine where it ended and died in 1806 attempting to trace its lower course S7. That second question — the river's mouth — was resolved only in 1830, when the British explorers Richard and John Lander travelled overland from Badagry to Bussa, then descended the river by canoe through its delta to the Atlantic via the Brass and Nun distributaries, weathering imprisonment by a local ruler along the way before reaching safety aboard a British ship S8. Their expedition, for which Richard Lander received the Royal Geographical Society's first monetary prize, finally answered a geographical question that had shaped decades of European exploration in West Africa and opened the river basin to the trading and colonial activity that followed S8. The river today remains central to Nigerian inland transport, forming the backbone of a c. 10,000 km navigable waterway network administered by the national inland waterways authority alongside the river benue, and its floodplain communities — including hausa people and nupe people settlements along the middle river and ijaw people and Ogoni communities in the delta — continue to depend on the seasonal rhythms the river sets S1S5S6