As defined by Pritchard (3), an estuary “is a semi-closed coastal body of water which has a free connection with the open sea and within which sea water is measurably diluted with fresh water derived from land drainage”. The first requirement based on the definition is the estuary being “a semi-closed system”. Its circulation pattern is largely affected by its lateral boundaries. This control by these boundaries is an important characteristic of an estuary which should be noted. Then the definition implies that an estuary is a feature of a coast, hence there should be a limit to size of the water bodies considered. In other words, the estuary is part of a coast and does not form the coast….