Long Lake

On the scoring rubric Long Lake grades a D: clarity at 2.8 ft and 48 µg/L of phosphorus keep it in the lower bracket for Washington County. Secchi readings are the weakest of the three parameters, suggesting suspended sediment or algal biomass dominates the optical signal.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. At 60 ft of maximum depth, Long Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. With 1,799 acres of surface and 16.8 miles of shoreline, Long Lake is a large water by Minnesota standards — recreational pressure is spread across a long shoreline. Long Lake ranks 63 of 83 in Washington County — at the lower end of the locally monitored distribution.

Zebra mussel presence at Long Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. Walleye are documented at Long Lake, one of 12 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. The lake has a partial ice record — 5 observed ice-outs, centered near Apr 8. Multiple sampling years from Minnesota PCA volunteers and partner agencies back the grade, so the letter should hold steady absent a major watershed shift.