San Juan County Lake Quality

San Juan County has 8 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. 1 of those lake carry recent nutrient and algae readings. The county-level summary describes that subset, not every water body listed. The county-wide picture is low-to-moderate phosphorus with clear summer transparency across most monitored lakes.

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. Little Eldorado Lake has the lowest nutrient and algae readings in the county.