And the Winner is … A Comparison of Various Approaches for Developing the Numeric Nutrient Criteria

More than 13 years after EPA urged the States to develop numeric nutrient criteria, nutrients are still among the top causes of waterbody impairments nationwide. While some States have made incremental progress, our national progress toward controlling nutrients has been disappointing. EPA has suggested several approaches for developing the numeric nutrient criteria – classification; reference condition; mechanistic models; stressor-response; multiple lines of evidence, scientific literature and expert judgment; and watershed-based planning. This paper discusses these and other approaches used by the States, and evaluates advantages, disadvantages, and challenges to implement them.It is clear that “one size fits all” may not be the best approach, since each waterbody is unique in its characteristics as well as in its response to nutrient loading and control methods. And the winner is … An equitable, adaptive and cooperative approach or a combination of approaches that involve all stakeholders, point and nonpoint sources.