NACWA Submits Comments on EPA’s Proposed Nutrient Criteria for Lakes and Reservoirs
(August 27, 2020) – NACWA recently submitted comments responding to a notice published in the Federal Register by EPA proposing to update its Ambient Water Quality Criteria Recommendations for Lakes and Reservoirs in the Conterminous United States and seeking input on its new methodology which will replace the Agency’s 2000-2001 ecoregional criteria.
NACWA’s comments noted appreciation for EPA’s effort to improve upon the previous nutrient criteria for lakes and reservoirs but expressed serious concerns with the idea that a national model could be used to derive individual or water body-specific criteria under the Clean Water Act’s Section 304(a). Instead, NACWA believes that the model and method proposed could be better applied as technical guidance as states develop criteria based on local management goals suitable for specific waterbodies.
Additionally, NACWA’s comments highlight concerns with requiring nitrogen and phosphorus concentrations for criteria derivation. NACWA also detailed the inappropriate and problematic use of proposed risk endpoints (e.g., zooplankton rate of change, vertical stratification, and cyanotoxin/microcystin) to derive criteria. Although EPA proposes an interesting statistical approach to relate risk endpoints, chlorophyll-a, and nutrient concentrations, NACWA has concern with EPA’s proposed Bayesian statistical approach both on the inherent variability with lake monitoring datasets and the low predictive power when aggregating data from many waterbodies and over large geographic scales.