Ripon Falls at the northern end of Lake Victoria in Uganda was formerly considered the source of the river Nile. In 1862–3 John Hanning Speke was the first European to follow the course of the Nile downstream after discovering the falls that his intuition had marked as the source of the Nile.
The water from Ripon Falls falls into a narrow opening and that is where some people believe the River Nile starts.
The Falls functioned as a natural outlet for Lake Victoria, until in 1954 the construction of Owen Falls Dam was completed, effectively extending Lake Victoria and submerging Ripon Falls.
This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Nile". Encyclopædia Britannica. 19 (11th ed.). Cambridge University Press. pp. 692–699. (See p. 694.)