Which components are included in a water quality standard?

• A. Designated uses, criteria, and antidegradation.
• B. Antidegradation only.
• C. Designated uses only.
• D. Numerical limits only.

Answer: (C)

Water quality standards are built around three elements: designated uses, water quality criteria, and the antidegradation policy. The designated uses specify what the waterbody should be able to support (like drinking water supply, recreation, or aquatic life). The water quality criteria translate those uses into measurable protections, providing either numeric pollutant limits or narrative conditions that must be met to safeguard the designated uses. The antidegradation policy guards existing high‑quality waters from unnecessary degradation by outlining when and how protections can be adjusted. All three together create a complete standard.

Saying the standard is only designated uses misses the essential protections provided by the criteria, which actually set the required water quality, and misses the broader protection framework of antidegradation. Saying it’s only antidegradation omits the designated uses and the concrete criteria needed to enforce those uses. Saying it’s numerical limits only ignores that criteria can be narrative and that the uses and antidegradation framework are also part of the standard.