This is Lokoja where the two largest rivers in West Africa merged in Lokoja, the Kogi State capital of Nigeria.
They are River Niger (Brownish) and River Benue (Greenish); they are the two largest rivers in both Nigeria and West Africa.
Both rivers meet at Lokoja Kogi State Nigeria forming a “Y” shape in what appears to be an extremely beautiful union and draining to the South.
Recall that all Rivers in Nigeria flow North-South direction with the exception of River Calabar which flows from south to northwards.