Lakes with Improving Water Quality

Which lakes are actually improving: multi-year EPA monitoring trends, the named recoveries still in progress, and what it takes to move a letter grade.

The lakes with the steepest multi-year declines in clarity and the sharpest rises in nutrients, what is driving the drop, and which ones may recover.

A data snapshot of the lakes we grade: how the A–F distribution breaks down, the clearest and the greenest states, and where the water is improving.

How lakes are graded A–F on nutrients and algae using EPA ecoregion condition classes, what each letter means in the water, and why an A is not a clearance.