Read the full profile
The River Gambia originates in Fouta Djallon in the mountain region of Western Guinea and flows through Senegal before entering the Gambia. Within the country, the River Gambia flows from east to west for about 400 km. It is a major waterway and tourist attraction. Its floodplains, riverbanks and wetlands are important habitats for wildlife and play an important role in local livelihood strategies. Its flow is highly seasonal. The maximum flow occurs at the end of the rainy season in late September or October with a flow of about 1 500 m3/s; the minimum dry season flow is less than 4.5 m3/s. Both measurements are taken at Gouloumbo in Senegal. Because of the flat topography there is a pronounced marine influence and the river’s seasonality and salinity have important repercussions on land use.
The country’s total actual renewable water resources are estimated at 8 km3/year, of which about 3 km3 are internally produced and the remaining 5 km3 represent the inflow of the River Gambia from Senegal (Table 2). It is estimated that internally produced groundwater amounts to about 0.5 km3/year, all of which is drained by the River Gambia and becomes the base flow of the river. Groundwater is available in all parts of the Gambia. The country is located in one of Africa’s major sedimentary basins and is often referred to as the Mauritania/Senegal Basin. It is characterized by two main aquifer systems with water table depths varying from 10 m to 450 m.
Along the river, the width of the valley varies from 20 to 40 km and three major sections may be distinguished:
- The Upper Valley (UV), where floods occur occasionally and water is always fresh.
- The Central Valley (CV), where tidal influence exists but water is also fresh. In the lower CV water is fresh only during the rainy season while in the dry season, when the salt tongue moves as far as 250 km upstream, it becomes brackish. Thus, in the dry season, about 220 km of freshwater are left in the Central and Upper River Divisions.
- The Lower Valley (LV), where water is perennially saline because of permanent tidal influence.