Summit County Lake Quality

Summit County holds 2 monitored lakes. 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 lakes carries an A–F grade, so the county-level summary covers the full set rather than a monitored subset. With an average grade of B, Summit County sits comfortably above the Colorado median.

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. Green Mountain Reservoir (A) is the cleanest in the county.