Columbia County Lake Quality

Columbia County holds 1 monitored lake. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. Every one of those lake carries an A–F grade, so the county-level summary covers the full set rather than a monitored subset. Columbia 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 Columbia (C) is the cleanest in the county.