A CHARACTERIZATION OF SOUTHERN AFRICAN ESTUARINE SYSTEMS

Abstract

Summary Modifications to the structure and functioning of southern African estuarine systems can be placed into two major categories; those changes that have been driven by global forces such as climatic and sea-level fluctuations, and those that have resulted from direct human interference and are of a local or regional nature. Both the above categories will determine the rate and magnitude of physiographic and hydrodynamic changes within southern African estuaries, and therefore have a major impact on the characterization of individual systems in the future. Although the fluctuating nature of southern African estuaries (on both a spatial and a temporal scale) makes it difficult to place individual systems in distinctive categories, a classification system is possible if the dominant conditions in a particular estuary are assessed. Using a combination of physiographic, hydrographic and salinity features, five types of systems are recognised in this review, viz. permanently open estuaries, temporarily open/closed estuaries, estuarine lakes, estuarine bays and river mouths. Examples are given of estuarine systems which have been characterized according to salinity regime, tidal prism, dominant mixing processes, freshwater inflow and mouth characteristics.