O'Brien County Lake Quality

O'Brien 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. Phosphorus and algae readings vary widely across O'Brien County; the per-lake pages below carry the numbers.

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. Dog Creek Lake has the lowest nutrient and algae readings in the county.