Missouri Lake Water Quality

Missouri lists 451 lakes across 93 counties, 165 of which carry a grade. Most of the input behind those grades flows through monitoring run by the Missouri Department of Natural Resources, which feeds state, federal, and volunteer measurements into the EPA Water Quality Portal. The remainder are here because they are real named lakes, not because anyone has sampled them recently. Around 25% of the graded lakes pull an A, 42 top-tier waters. The B and C brackets together hold most of the rest, with the F bracket capturing 46 stressed lakes mostly in the agricultural south of the state.

Stockton Lake is the largest lake in this index at about 24,900 acres, one of 21 here that clear 500 acres. The rest run smaller, and small and shallow is where nutrient loading shows up first, because there is less water to dilute it and the bottom sediment stays within reach of the sun. The graded lakes lean eutrophic, with enough nutrient input to support an active algal community and the trade-offs in clarity and dissolved oxygen that come with it. The cleanest county on average is Clark (grade A); the most-stressed is Wayne. The gap between the top and bottom counties is large enough that a single figure for Missouri lake water quality hides real local variation.