What is a water quality standard, and which section governs its development?

• A. A standard consists of designated uses, criteria, and antidegradation; developed under Section 303.
• B. A standard is only the amount of pollutants allowed, developed under Section 402.
• C. A standard is the water's temperature alone.
• D. A standard is the color of water.

Answer: (A)

Water quality standards define what level of quality a water body must meet to support its designated uses, and they include three parts: designated uses (the purposes the water should serve), water quality criteria (the numeric or narrative limits that protect those uses), and an antidegradation policy (to protect high-quality waters from degradation). They are developed by states or authorized tribes under Section 303 of the Clean Water Act, with EPA approval after public input. This combination—uses, criteria, and antidegradation—under the 303 process is what makes a water quality standard, not just a single pollutant limit or a trivial property like temperature or color.