The Secretary of State may, in relation to any description of controlled waters (being a description applying to some or all of the waters of a particular class or of two or more different classes), by regulations prescribe a system of classifying the quality of those waters according to criteria specified in the regulations.
The criteria specified in regulations under this section in relation to any classification shall consist of one or more of the following, that is to say—
general requirements as to the purposes for which the waters to which the classification is applied are to be suitable;
specific requirements as to the substances that are to be present in or absent from the water and as to the concentrations of substances which are or are required to be present in the water;
specific requirements as to other characteristics of those waters;
and for the purposes of any such classification regulations under this section may provide that the question whether prescribed requirements are satisfied may be determined by reference to such samples as may be prescribed.