Oklahoma Lake Water Quality

150 of the 319 Oklahoma lakes in this index carry a recent clarity, phosphorus or algae reading, spread over 71 counties. Those readings come from the Oklahoma Department of Environmental Quality, alongside federal programs and volunteer monitoring networks. The rest are listed for their size, depth and location, with no recent nutrient or algae sampling behind them. Low nutrient readings are less common among Oklahoma's measured lakes. The smaller, agricultural-watershed lakes that dominate the measured set tend to carry persistent phosphorus loads.

Oologah Lake is the largest lake in this index at about 29,729 acres, one of 83 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. Eutrophic conditions dominate the measured set: nutrient-loaded, productive, with algal pressure that shows up most years in late summer. These lakes tend to be shallow, in agricultural watersheds, and over-warmed by the time July ends. The county with the lowest nutrient and algae readings on average is Grayson. The gap between counties is large enough that a single figure for Oklahoma lake water quality hides real local variation.