Deriving nutrient criteria to minimize false positive and false negative water use impairment determinations

ABSTRACT

Smeltzer E, Kamman NC, Fiske S. 2016. Deriving nutrient criteria to minimize false positive and false negative water use impairment determinations. Lake Reserv Manage. 32:182–193.

Nutrient water quality criteria for lakes and wadeable streams in Vermont were derived using receiver operating characteristic (ROC) analysis to evaluate false positive and false negative error rates in making water use impairment determinations. Numeric nutrient criteria for total phosphorus (TP), chlorophyll a (Chl-a), and Secchi depth were derived to protect aesthetic uses in lakes in a manner that balanced and minimized these 2 types of errors. TP and total nitrogen (TN) criteria were derived to protect aquatic life uses in wadeable streams. The resulting criteria for lakes were TP = 17−18 µg/L, Chl-a = 3.8−5.2 µg/L, and Secchi depth = 2.6−3.2 m, depending on the applicable tiered water use objective defined in the state's water quality standards. Wadeable stream criteria were TP = 9−27 µg/L and TN = 0.25−1.3 mg/L, depending on the designated water use and the stream macroinvertebrate community type. These criteria, with some modifications and with the exception of TN, were incorporated into the Vermont Water Quality Standards as part of an integrated nutrient criteria framework.

KEYWORDS:

• aquatic life use
• chlorophyll-a
• nitrogen
• nutrient criteria
• phosphorus
• receiver operating characteristic
• Secchi depth
• use impairment
• Vermont

Acknowledgments

We thank L. Yuan from the US EPA Office of Science and Technology for pointing out the potential for sampling bias to affect the analysis of false positive and false negative error rates and for suggesting the solution involving logistic regression. Three anonymous reviewers provided constructive comments that improved the manuscript.

Funding

This work was supported by Vermont DEC and grants from the US EPA.