Vermont Lake Water Quality

134 of the 308 Vermont lakes in this index carry a recent clarity, phosphorus or algae reading, spread over 14 counties. Those readings come from the Vermont Department of Environmental Conservation, 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 and algae readings are common among measured Vermont lakes, mostly the cold, deep, kettle-formed lakes in the north of the state, which buffer themselves against nutrient inputs.

Lake Bomoseen is the largest lake in this index at about 2,360 acres, one of 19 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. Mesotrophic is the dominant trophic class among the measured lakes, a workable middle ground between the pristine oligotrophic deep lakes and the algal-pressured eutrophic shallow ones. Orange has the lowest nutrient and algae readings on average. With only 14 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.