Grand County Lake Quality

There are 25 monitored lakes in Grand County. The mix is varied enough that the county-level average tells you the broad strokes, not the choose-this-cabin specifics. 6 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. Grand County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.

Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Lake Granby Dam Bottom (B) is the cleanest in the county.