Beaverhead County Lake Quality

There are 28 monitored lakes in Beaverhead County. The mix is varied enough that the county-level average tells you the broad strokes, not the choose-this-cabin specifics. 1 of those lake carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.

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. Clark Canyon Reservoir (C) is the cleanest in the county.