The answer to the crossword is 'NILE', which is a major river in Africa. Its branches are white and blue, referring to the White Nile and Blue Nile, two of the main tributaries of the Nile River. The White Nile originates in Lake Victoria in Uganda and flows northward through Sudan and Egypt, while the Blue Nile originates in Ethiopia and flows into Sudan before joining the White Nile in Khartoum.