Armstrong County Lake Quality

Armstrong County has 2 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. Every one of those lakes carries recent nutrient and algae readings, so the county-level summary covers the full set rather than a monitored subset. The county-wide picture is low-to-moderate phosphorus with clear summer transparency across most monitored lakes.

Many of the county's lakes are deep glacial basins, over 50 feet at their deepest point, which gives them thermal stratification and a buffer against summer warming. Keystone Lake has the lowest nutrient and algae readings in the county.