Senegal occupies 196,722 square kilometers on the westernmost bulge of the African continent. The country shares borders with Mauritania to the north, Mali to the east, Guinea and Guinea-Bissau to the south, and almost completely surrounds The Gambia, which forms a narrow enclave following the Gambia River inland for approximately 300 kilometers. The Atlantic Ocean defines Senegal's western boundary across roughly 530 kilometers of coastline. This position gives Senegal the distinction of containing Cap-Vert on the Cape Verde Peninsula, which at 17°33'22"W stands as the westernmost point of mainland Africa. The country's shape and river systems create distinct ecological zones that transition from Sahel scrubland in the north to tropical forests in the southern Casamance region.
The Senegal River forms the entire northern border with Mauritania, flowing approximately 1,086 kilometers from its source in Guinea through Mali before defining this international boundary and emptying into the Atlantic at Saint-Louis. The river's flow varies dramatically between seasons. Annual flooding once deposited nutrient-rich sediments across the Fouta Toro region and the river's delta, supporting agriculture and creating wetlands that attracted massive bird populations. The construction of the Diama Dam near the mouth in 1986 and the Manantali Dam in Mali in 1988 fundamentally altered this hydrological pattern. The Diama Dam prevents saltwater intrusion during dry season low flows, while Manantali regulates water release for irrigation and hydroelectric generation. These engineering projects eliminated the natural flood pulse that defined the river's ecology for millennia. The Senegal River delta at Saint-Louis covers approximately 16,000 hectares and includes the Langue de Barbarie, a narrow sand spit that separates the river's final reach from the Atlantic. In 2003, local residents breached this spit to prevent flooding in Saint-Louis, creating a new outlet that has since widened from four meters to approximately six kilometers, fundamentally reshaping delta hydrology and threatening coastal communities with erosion.
The Gambia River enters Senegal from Guinea and flows west-northwest through the country before entering The Gambia proper. Although most of its 1,120-kilometer length lies outside Senegalese territory, the river influenced historical settlement patterns and trade routes. The Casamance River defines southern Senegal, flowing approximately 300 kilometers from Guinea-Bissau westward to the Atlantic at Ziguinchor. Unlike the Senegal River, the Casamance remains tidal for most of its length, with saltwater penetrating far inland during dry season. This estuarine character creates extensive mangrove forests along its banks, covering approximately 170,000 hectares in the wider Casamance region. The Saloum River system north of The Gambia creates an intricate delta where freshwater rivers meet Atlantic tides, forming the Sine-Saloum Delta. This delta covers approximately 180,000 hectares and contains over 200 islands and islets formed from accumulated shells deposited over centuries by mollusk populations that thrived in the brackish conditions.
Senegal's topography offers minimal dramatic relief. The highest point, an unnamed feature in the Fouta Djallon foothills near the southeastern border with Guinea, reaches only 581 meters above sea level. Most of the country consists of low plateaus rarely exceeding 100 meters elevation. The Dakar Peninsula represents one exception, where volcanic rocks from ancient activity create modest hills that give the capital city its varied terrain. The Niayes region extends along the coast from Dakar north to Saint-Louis, characterized by a series of sand dunes and interdune depressions where the water table approaches the surface. These depressions, called niayes, support year-round agriculture including market gardens that supply Dakar with vegetables. The Ferlo region in north-central Senegal consists of semi-arid plains with sandy soils and sparse vegetation dominated by acacia trees. This area experiences extreme temperature variation, with daytime highs regularly exceeding 45°C during April and May before monsoon rains arrive.
The country experiences a tropical climate with a single rainy season driven by the West African monsoon's northward migration between June and October. Rainfall varies dramatically from north to south. Saint-Louis in the north receives approximately 300 millimeters annually, while Ziguinchor in Casamance receives approximately 1,500 millimeters. This gradient creates corresponding vegetation zones. The Sahel climate in northern Senegal supports only drought-resistant grasses and scattered acacia trees. The Sudanian savanna zone across central Senegal contains more substantial tree cover including baobabs, whose massive trunks store water to survive the eight-month dry season. The southern Casamance region receives sufficient rainfall to support gallery forests along watercourses and areas of dense woodland. Temperature patterns show less variation. Coastal areas benefit from Atlantic breezes that moderate temperatures, keeping Dakar's average between 18°C and 28°C year-round. Interior locations experience wider swings, particularly in the Ferlo where nighttime temperatures during December and January can drop to 10°C.
The Harmattan wind shapes Senegalese climate and daily life from November through March. This dry northeasterly wind originates in the Sahara Desert and carries fine dust particles that reduce visibility, sometimes to less than one kilometer. The dust contains silica particles and can irritate respiratory systems. Harmattan conditions create distinctive hazy skies that obscure the sun and coat surfaces with fine reddish powder. The wind's extreme dryness causes rapid evaporation and can crack human skin. Humidity during peak Harmattan periods in December and January drops below ten percent in northern Senegal. The phenomenon ends when monsoon circulation patterns shift and southwesterly winds from the Atlantic begin advancing northward, typically in late May or early June. This transition period brings dramatic humidity increases but little rain until the monsoon fully establishes, creating uncomfortable sticky conditions before the first substantial rains arrive.
Lake Retba, also called Lac Rose, lies approximately 35 kilometers northeast of Dakar near the Atlantic coast. This shallow lagoon covers roughly three square kilometers and reaches maximum depths of only three meters. The lake's fame derives from its pink coloration, caused by Dunaliella salina algae that produce red pigment to protect against intense sunlight. Color intensity varies with season and time of day, appearing most vivid during dry season months from November to June when sunlight intensity peaks and water levels drop. The lake contains salt concentrations reaching 380 grams per liter, comparable to the Dead Sea and approximately ten times ocean salinity. This extreme salinity prevents most organisms from surviving but allows Dunaliella salina to thrive without competition. Salt harvesting from the lake provides employment for approximately 1,000 workers who wade into the water and extract salt by hand, loading it into wooden pirogues. The lake's eastern shore gained different fame as the finish line for the Paris-Dakar Rally from 1979 until the event relocated to South America in 2009 due to security concerns in Mauritania and Mali.
The Sine-Saloum Delta where the Saloum River meets the Atlantic creates one of West Africa's most important wetland ecosystems. This maze of channels, islands, and mangrove forests covers approximately 180,000 hectares and was designated a UNESCO World Heritage Site in 2011 for both natural and cultural significance. The delta contains 218 archaeological sites including 28 shell middens, some reaching ten meters high and containing millions of shells discarded by communities who harvested mollusks here over two millennia. Radiocarbon dating places some middens at 2,000 years old. These shell mounds also contain human burials, with over 200 individuals discovered in tumuli excavations. The delta's mangrove forests include four species: Rhizophora racemosa, Rhizophora mangle, Rhizophora harrisonii, and Avicennia germinans. These mangroves provide critical nursery habitat for juvenile fish, protect shorelines from erosion, and sequester carbon at rates exceeding most terrestrial forests. The delta supports approximately 72,000 residents across 313 villages who practice fishing, shellfish gathering, and salt production.