Lewis and Clark County Lake Quality

There are 16 monitored lakes in Lewis and Clark 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-wide average grade is D — water quality issues are persistent across most of the monitored basins. 0 lakes fall into the F bracket outright.

The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Lake Helena Outlet (D); the most-stressed is Lake Helena Outlet (D).