West Virginia is required to establish nutrient criteria under a mandate from EPA. The West Virginia Environmental Quality Board established the Nutrient Criteria Committee (NCC) as a technical working group in 2002 that was charged with recommending nutrient criteria for lakes and reservoirs. West Virginia proposes criteria for TP and chlorophyll a to protect aquatic life and recreational uses. According to the state, the weight of evidence indicates that standards less stringent than those proposed by EPA will adequately protect water bodies.
The authors of this report recommend adopting a TP criterion that will ensure that DO is sufficient in the epilimnion. A TP criterion of 30 µg/L mean for cool water lakes and 50 µg/L mean for warm water lakes is recommended based on results of literature studies, data analyses, and user surveys.
The authors propose adopting the chlorophyll a criteria proposed by the Virginia Academic Advisory Committee. A chlorophyll a criterion of 10 µg/L mean for cool water lakes and 25 µg/L mean for warm water lakes was recommended based on statistical analyses.
Researchers used linear regression to compare the average of all TP values in a lake with the minimum DO value measured in that lake. While the average TP reflects the general condition and characteristics of the lake, the minimum DO reflects that lake’s response to climatic conditions most likely to deplete oxygen from the entire lake, so that even the epilimnion is hypoxic. The objective of the analysis was to identify average TP concentrations at which there was a substantial risk of DO dropping below 6 mg/L during the daytime, when the measurements supporting the analysis were made.
User surveys were helpful in determining the levels at which nutrients and nutrient-related parameters protect the water contact recreation use. Survey results and monitoring data were analyzed to determine the levels of TP that correspond to user perceptions that the lake water is unsuitable for recreation.
Because chlorophyll a levels are a response to the TP levels in a lake, a comparison of all TP measurements collected on the same day as chlorophyll a measurements was used to link a chlorophyll a standard level to a TP standard level. The regression was highly significant and explained approximately 16 percent of the variation. The relationship is used with various TP levels to determine corresponding chlorophyll a levels and to select an appropriate chlorophyll a criterion (Hansen et al. 2006).
Reference:
Hansen, E., M. Christ, J. Janes, J. Hankins, and N. Gillies. 2006. Recommended Nutrient Criteria for West Virginia Lakes. Prepared for West Virginia Department of Environmental Protection. Accessed October 2016. http://www.dep.wv.gov/WWE/Programs/wqs/Documents/Triennial%20Review/April%2028,%202006/10391_Environmental_Interests_Position.pdf EXIT.