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Geography & Natural Habitats of Gambia

Climate    Coastline     River Gambia
The Gambia is situated in the Sahelian zone on the West Coast of Africa. It is one of the smallest countries in Africa (the smallest being  Seychelles archipelago) and has a total area of 11,300 square km, of which about 20 percent is described as wetland. The river runs from east to west, dividing the country in two strips of land 25 to 50 km wide and about 300 km long.

The country has a total boundary length of 820 km (510 mi), of which 80 km (50 mi) is coastline. The River Gambia, the country's major waterway, rises in Guinea and follows a twisting path for about 1,600 km (1,000 mi) to the sea.

A flat plateau of tertiary sandstone, capped with an infertile ironstone crust, gently rises from 10- 15 m at the coast to 100 m at 400 km inland. The rest of the catchments consists of older worn Paleozoic and Pre-Cambrian rock with a maximum height of about 1500 m in the Fouta Djallon. Pleistocene and Holocene (Nouakchottian transgression) exist along the coast, along the estuaries and in river valleys.

The landscape two major geomorphologic units can be distinguished between the uplands and the lowlands:

On the upland plateaus, weathered tropical soils are found. These soils have low intrinsic fertility and low water retention capacity, but their drainage conditions are good. The plateau is intersected by watercourses flowing downwards on the lowlands. These streams have formed narrow fluvio colluvial valleys (Wulumbangos).

The lowlands include the floodplain of the River Gambia in the Upper Valley, and tidal plains (Banta Faros) in the Central Valley and Lower Valley. The soils of the lowlands are flat, fine textured and poorly drained. In the LV potentially acid sulphate soils occur, which can become acidic soils unless water logging is prevented by drainage.

Water Resources:
Outside salinity risk areas (Scott Wilson Kirkpatrick, 1993), freshwater can be found throughout The Gambia, at depths ranging from 4 to 30 mbgl (metres below ground level). In general, depths increase with proximity to the border with Senegal. Groundwater recharge depends on the quantity and spatial and temporal distribution of rainfall, surface geology, and land use (Howard Humphreys and Sons, 1974; Chow, 1964). Good quality surface water within the country is only found in the eastern third of the River Gambia. From June to December, freshwater availability is boosted by flows from the middle and upper Gambia River Basin areas. Low flows from January to May are mostly sustained by local rainfall (Njie, 2002).

Natural Habitats:
The main feature of the land is predominantly Guinea woodland savannah and Sahelian scrub with with mangroves concentrated near the estuary of the River Gambia and along its banks and Bolongs.

The vegetation is comprised of the Savannah type with shrub and grass understoreys. Mangroves are found in the western half of the country in the floodplains of the river region. The cultivable land area is roughly 430,000 hectares, which is 38 percent of the total area. Back in 2002 available arable land was 250,000 hectares, while 5,000 hectares were under permanent crops.
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