Possible Clues:

• River that rises in Ethiopia's Lake Tana
• White meets this other shade at Khartoum
• Not the colour of the flower that starts out from Victoria
• Not the white river
• The wind on the river, by the sound of it, was not the white one
• Ethiopian river
• Coloured wriggly line on map of Africa
• Like the Danube of Africa
• In Africa it flows down meandering line
• River with a 'White' counterpart