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Estuaries in NSW

Estuarine Water Quality

Composition of Estuarine Waters

Within an estuary, the composition of water - or "water quality" - is determined by the interaction of the following processes:

imports and exports of materials (particulate, dissolved and gaseous) via freshwater flows, coastal flows and the atmosphere
physical transport and mixing (advective and dispersive transport)
energy inputs in the form of light and heat
chemical transformations, and
biological processes.

Although the basic physical and chemical processes are well understood, their interactions are very complex. Far less is known of the effects of biological processes on water quality. The effects of water quality on ecosystems, especially longterm impacts, are also poorly understood.

Major factors determining the composition of estuarine waters are land-based runoff, seawater and "point" sources of pollution such as sewage and industrial effluent discharges. The composition of land-based runoff and point sources of pollution is quite variable, depending upon catchment and industrial activities. The composition of seawater is relatively stable.

Parameters contributing to estuarine water quality may be classified as follows:

suspended solids (particulate and colloidal matter)
dissolved solids (including salts and organic compounds)
floating matter (including oil, scum and debris)
dissolved gases, and
temperature (hot and cold water inputs).

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