The Sénégal's headwaters are the Semefé (Bakoye) and Bafing rivers which both originate in Guinea; they form a small part of the Guinean-Malian border before coming together at Bafoulabé in Mali. From there, the Senegal river flows west and then north through Talari Gorges near Galougo and over the Gouina Falls, then flows more gently past Kayes, where it receives the Kolimbiné. After flowing together with the Karakoro, it prolongs the former's course along the Mali-Mauritanian border for some tens of kilometers till Bakel where it flows together with the Falémé River, which also has its source in Guinea, subsequently runs along a small part of the Guinea-Mali frontier to then trace most of the Senegal-Mali border up to Bakel. The Senegal further flows through semi-arid land in the north of Senegal, forming the border with Mauritania and into the Atlantic. In Kaedi it accepts the Gorgol from Mauritania. Flowing through Bogué it reaches Richard Toll where it is joined by the Ferlo coming from inland Senegal's Lac de Guiers. It passes through Rosso and, approaching its mouth, around the Senegalese island on which the city of Saint-Louis is located, to then turn south. It is separated from the Atlantic Ocean by a thin strip of sand called the Langue de Barbarie before it pours into the ocean itself.The river has two large dams along its course, the multi-purpose Manantali Dam in Mali and the Maka-Diama dam on the Mauritania-Senegal border, near the outlet to the sea, preventing access of salt water upstream.
In the Early Middle Ages (c.800 CE), the Senegal River restored contact with the Mediterranean world with the establishment of the Trans-Saharan trade route between Morocco and the Ghana Empire. Arab geographers, like al-Masudi of Baghdad (957), al-Bakri of Spain (1068) and al-Idrisi of Sicily (1154), provided some of the earliest descriptions of the Senegal River. Early Arab geographers believed the upper Senegal River and the upper Niger River were connected to each other, and formed a single river flowing from east to west, which they called the "Western Nile" or the "Nile of the Blacks". It was believed to be either a western branch of the Egyptian Nile River or drawn from the same source (variously conjectured to some great internal lakes of the Mountains of the Moon, or Ptolemy's Ghir or the Biblical Gihon stream).
Western Nile (Senegal-Niger River) according to al-Bakri (1068)Arab geographers Abd al-Hassan Ali ibn Omar (1230), Ibn Said al-Maghribi (1274) and Abulfeda (1331), label the Senegal as the "Nile of Ghana" (Nil Gana or Nili Ganah).