 The four major rivers, the Senegal River, the Saloum River, the Gambia River and the Casamance River, drain westwards into the Atlantic Ocean.The Lac de Guiers is a large freshwater lake in the north of the country while Lake Retba, near Dakar, is saline.The northern half of the country has an arid or semi-arid climate and is largely desert while south of the Gambia River the rainfall is higher and the terrain consists of savannah grassland and forest.