(May 28, 2020) – In a departure from its much-criticized eco-regional approach to developing nutrient criteria, EPA published draft water quality criteria recommendations for lakes and reservoirs in the May 22 Federal Register that rely on statistical, stressor-response relationships using data collected from hundreds of lakes.

In the new draft criteria, EPA developed a national model that, according to the Agency’s Press Release, will allow states to “incorporate local data…to help develop numeric nutrient criteria.” NACWA raised serious concerns with EPA’s original eco-regional approach and few states have opted to use the approach given its shortcomings. The new criteria utilize stressor-response relationships that NACWA has also raised concerns about, namely that increased levels of nutrients (the stressors) do not always result in predictable impacts to water quality (the response).

In real-world conditions, there are numerous variables that must be taken into account for every waterbody in order to fully and accurately assess the impacts. NACWA has not yet reviewed the new criteria in detail, so it is not clear to what degree EPA’s new national model will factor in these other variables. How adaptable the national model is and whether it can reliably relate nutrient levels to actual in-water impacts will be a key focus of NACWA’s review with its Water Quality Committee in the coming weeks.

NACWA plans to file comments by the July 21 deadline. Members with questions or input can contact Chris Hornback.