The tropical climate also produced the Congo River system which dominates the region topographically along with the rainforest it flows through, though they are not mutually exclusive. The name for the Congo state is derived in part from the river. The river basin (meaning the Congo River and all of its myriad tributaries) occupies nearly the entire country and an area of nearly . The river and its tributaries form the backbone of Congolese economics and transportation. Major tributaries include the Kasai, Sangha, Ubangi, Ruzizi, Aruwimi, and Lulonga.