Water quality objectives, criteria, and standards are interrelated but different from one another. A water quality objective is a goal toward which a control program is aimed. For example, an objective of Public Law 92-500 was to eliminate discharge of all pollutants into navigable streams by 1985. Objectives often represent an ideal condition.
Water quality criteria, on the other hand, represent specific, though not necessarily precise, quality characteristics that research and experience indicate are generally necessary to support various water uses. They provide a measure of suitability of water quality for a particular use and what magnitude of change is needed to make it suitable.
Water quality standards differ from objectives and criteria in that they represent measures required by laws or regulations. They tend to be rigid and absolute and are either met or violated. Standards provide the "teeth" for water quality legislation and also the yardstick by which performance can be evaluated. Water quality standards generally are related directly to the specific quality criteria for uses to be protected.
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