ABSTRACT
Water quality is very hard to defi ne and to a great extent extremely subjective. It is not simply a case of the cleaner or purer the better. For example, distilled water is extremely pure chemically and so its quality can be considered as being high as it contains no toxicants or pollutants, yet it is unsuitable for potable use and it lacks the trace elements necessary for freshwater biota. Water quality can only be defi ned in relation to some potential use for which the limiting concentrations of various parameters can be identifi ed. This approach makes particular sense as concern for quality is normally related to some practical need (e.g. drinking, fi shing, agriculture, etc.).
