Lagoons
A water body which is deemed to be too big to be called a pond and too small to be called a lake is often popularly called a lagoon. Here the term is restricted to the definition given by the National Geographical Society, namely that a lagoon is "a shallow body of water protected from a larger body of water (usually the ocean) by sandbars, barrier islands, or coral reefs". In Ghana, the term 'lagoon' is applied not only to coastal but also to inland features that fall within the spirit of this definition, where the 'larger body' of water may be a river rather than the Gulf of Guinea, hence the division of this category into Coastal Lagoons and Riverine Lagoons.
Coastal Lagoons
In a 2007 report compiled for the Environmental Protection Agency, W. K. Tamakloe gives a useful description of Ghana's coastal lagoons:
Over 90 coastal lagoons fringed by intertidal mud or sandflats and in some places by mangrove swamps occur along the coastline of Ghana. The lagoons form important vulnerable ecosystems, housing a wide variety of fish, shrimps, crabs, mollusc and polychaete species. Some of the lagoons have been recognized both nationally and internationally as migratory waterbird habitats (Ntiamoa-Baidu & Grieves 1987, Ntiamoa-Baidu 1991, 1993) while some may serve as nursery areas for juveniles of marine fish and shrimp.
Two main types of coastal lagoons are encountered in Ghana. These are ‘open’ and ‘closed’ lagoons (Armah 1991). The open lagoons have a permanent opening to the sea and are normally fed by rivers that flow all year round. They occur mostly on the central and western parts of the coastline where higher rainfall results in a more continuous flow of the rivers and streams.
The closed lagoons are separated from the sea by a sand barrier. They are more common on the eastern segments of the coastline where rainfall is low and highly seasonal. Some closed lagoons open to the sea in the rainy season when floodwaters break the sand barrier (Kwei, 1977). Storm surges may also erode sandbars and open up closed lagoons to the sea (Armah, 1991). Under other circumstances the sandbar may be manually breached during the rainy season to reduce the risk of flooding adjacent settlements where this is considered a threat.
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References.:Armah, A.K. (1991): Coastal erosion in Ghana; causes, patterns, research needs and possible solutions Coastal Zone 91: 2463-2473Kwei, E.A. 1977. Biological, Chemical and Hydrological Characters of Coastal lagoons of Ghana, West Africa. Hydrobiol. 56: 157-174Ntiamoa-Baidu Y. (1991). Seasonal changes in the importance of coastal wetlands in Ghana for wading birds. Biol. Conserv. 57: 139–158.Ntiamoa-Baidu Y. (1993). Trends in the use of Ghanaian coastal wetlands by migrating Knots. Calidris canutus. Ardea 81: 71–79Ntiamoa-Baidu Y. and Grieves A. (1987). Palearctic waders in coastal Ghana in 1985/ 86. Wader study group Bulletin 49, suppl. / IWRB spec. Pub. 7:76–78Riverine Lagoons
The term 'lagoon' as applied to water features associated with rivers can be found on old maps of Ghana, for example the U.S. Army Map Service, Series G504, 1:250,000 available from the University of Texas Libraries, illustrated below for the White Volta. In some cases these water bodies may have been formed by a process of erosion, as with oxbow lakes; in others they may be seasonally dependent owing to their position on flood plains.
The description as 'riverine', though logical, is not commonly used, but precedents exist, as on the website Spirit of the Land, which describes the locality of Luwi Lagoon, Zambia, as "the riverine lagoon habitat that outlies the course of the main Luangwa River". A comparison of a satellite image of this area with one of the same stretch of the White Volta, shows the striking similarity of both the lagoons and their geographical setting.
White Volta, US Map NC30-12
White Volta, 1.0W, 9.7N
Luangwa River, 31.9E, 13.0S