The country owes its former name of Upper Volta to three rivers which cross it: the Black Volta (or ''Mouhoun''), the White Volta (''Nakambé'') and the Red Volta (''Nazinon''). The Black Volta is one of the country's only two rivers which flow year-round, the other being the Komoé, which flows to the southwest. The basin of the Niger River also drains 27% of the country's surface.