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LakeQuality

Hypereutrophic lakes (TSI above 70) are at the upper end of the productivity scale: visible algal blooms most weeks of summer, clarity often under 3 feet, and meaningful risk of harmful-algal-bloom toxin events. 4 hypereutrophic lakes are on the Tennessee books. Almost none of them are deep — 0% break 50 feet. Shallow basin plus heavy nutrient input is the consistent recipe.

Hypereutrophic lakes overwhelmingly grade D or F — the trophic class and the grade are measuring closely-related dimensions of the same underlying nutrient regime.

#LakeCountyGradeClarityDepthTSI
1Duck River LakeHumphreysD--81
2Reelfoot Lake Blue BasinLakeD--83
3Reelfoot Lake Upper Blue BasinObionD--85
4Reelfoot Lake-Reelfoot Creek EmbaymentObionD--80

Source: EPA National Aquatic Resource Surveys, 2026.