With basic water quality objectives, the environmental requirement is that living conditions have to be assured for a varied and natural flora and fauna, unaffected or only slightly affected by human activity.

With stringent water quality objectives, the environmental requirement are more stringent than those of areas with basic quality objectives, this being warranted by special circumstances, e.g. the presence of rare animals and plants, bathing water quality requirments, etc.

With eased water quality objectives, it is accepted that human activity renders it unlikely that the basic quality objectives will be fulfilled. Possible reasons include the discharge of sewage, the abstraction of raw materials or water, waste depositories, harbour facilities, etc. when such activities are considered more important, or because it is not possible to propose means whereby the basic quality objectives could be fulfilled.