2 - Estuarine water circulation

Abstract

The physical functioning of estuarine water and sediment varies greatly from estuary to estuary because estuaries can take many shapes and sizes, and because the external physical forcings by river flows, sediment, tides, wind, and evaporation also vary for each one. The hydrodynamic regime of estuaries is the combined result of several components, including the currents and mixing processes caused by the interaction between freshwater and seawater; the tides with their semi-diurnal, diurnal, weekly, fortnightly, equinoctial, and annual cycles; the wind, rainfall and evaporation; oceanic events in coastal waters such as an upwelling, the passage of oceanic eddies, and storms; and the spatially and temporally varying bathymetry and geomorphology, so that an estuary is never at a steady state. This chapter details the net result of these features to give the overall water circulation patterns, which form the basic functioning of an estuary.