FTN Associates Inc., conducted a study for the Arkansas Department of Environmental Quality (DEQ) to develop nutrient-related criteria for Beaver Lake, a major source for drinking water and recreation. The researchers used a weight-of-evidence approach, which allows weighted consideration of several research components in a final recommendation. One of the lines of evidence used was water quality modeling, using both TSTR (a modification of the BATHTUB model) and CE-QUAL-W2. The researchers also considered nutrient criteria in the literature, historical trends in water quality, ecoregion recommendations through the EPA, percentile values for reference lakes, statistical analysis of Beaver Lake, and nutrient-loading relationships. All evaluated information was compared with measured water quality data obtained from the U.S. Geological Survey, DEQ, and other sources. The researchers made recommendations for chlorophyll a, Secchi transparency, TP, and TN. DEQ adopted the recommended values for chlorophyll a and Secchi transparency as site-specific nutrient criteria for Beaver Lake (FTN Associates 2008).
Although the recommended values were adopted as criteria, the values have been criticized as too conservative, resulting in a false positive assessment of impairment. Scott and Haggard (2015) argue that the FTN suggested values are average conditions and, therefore, result in the immediate listing of Beaver Lake as impaired.
References:
FTM Associates (FTN Associates, Ltd.). 2008. Beaver Lake Site-Specific Water Quality Criteria Development: Recommended Criteria. FTN No. 3055-021. Accessed October 2016. https://www.adeq.state.ar.us/regs/drafts/reg02/13-003-r/comments/reg_2_comments_bwd_attachment_1.pdf Exit.
Scott, J.T., and B.E. Haggard. 2015. Evaluating the Assessment Methodology for the Chlorophyll-a and Secchi Transparency Criteria at Beaver Lake, Arkansas. Prepared for Beaver Watershed Alliance. Arkansas Water Resources Center, Publication MSC 372. Accessed October 2016. http://arkansas-water-center.uark.edu/publications/msc/MSC372_Beaver-Lake-Chlorophyll-a-and-secchi-criteria.pdf Exit.