Validation of Candidate Nutrient Screening Thresholds for Freshwater Wadeable Streams in Virginia

Abstract

This report details the activities and findings of Task 2 of the Academic Research Group (ARG) to the Virginia Department of Environmental Quality (DEQ) for fiscal year (FY) 2026. The goal of this activity was to test how well nutrient candidate thresholds proposed by the Academic Advisory Committee (AAC) in 2016 for wadeable freshwater streams of Virginia's Mountain and Piedmont ecoregions predict the impairment status of streams when using monitoring data collected since 2014. Using data collected since 2014 yielded in the following results: 1) The no-observed effect thresholds are largely reproducible and differ between ecoregions; and 2) The observed-effect concentrations are almost never exceeded and are thus operationally limited.