Utah Lake Water Quality

Utah lists 304 lakes across 29 counties, 117 of them with a recent water-quality reading. Most of that sampling flows through monitoring run by the Utah Division of Water Quality, 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. A large share of the state's measured lakes carry low phosphorus and chlorophyll-a readings, which reflects the depth and natural nutrient poverty of glacial lakes in the region.

Sevier Lake is the largest lake in this index at about 122,528 acres, one of 24 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. Most measured Utah lakes sit in the mesotrophic band: moderate productivity, decent clarity, capable of supporting both warm-water and cool-water fisheries. This is the band where well-managed working lakes tend to land. Millard has the lowest nutrient and algae readings on average. With only 29 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.