The Clean Water Act’s (CWA) Section 301(m)(2) reads: “The effluent limitations established under a permit issued under paragraph (1) shall be sufficient to implement the applicable State water quality standards, to assure the protection of public water supplies and protection and propagation of a balanced, indigenous population of shellfish, fish, fauna, wildlife, and other aquatic organisms, and to allow recreational activities in and on the water. In setting such limitations, the Administrator shall take into account any seasonal variations and the need for an adequate margin of safety, considering the lack of essential knowledge concerning the relationship between effluent limitations and water quality and the lack of essential knowledge of the effects of discharges on beneficial uses of the receiving waters.”
Neither a permit holder, nor a regulatory agency, can demonstrate compliance with the CWA without data on local aquatic biota and wildlife (protection of indigenous populations of biotic organisms) when water chemistry samples are acquired. The other essential compliance elements are measurements of temporal variability (such as seasonal) and how water chemistry is related to specific beneficial uses (based on local taxa and consumption of water) in the waterbody being assessed.