Pool of Lake St. Croix

The LakeGrade rubric puts Pool of Lake St. Croix at a C: clarity at 4.3 ft, 39 µg/L of phosphorus, and a TSI of 57 signal an intermediate trophic state. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

At a TSI of 57, Pool of Lake St. Croix reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. Pool of Lake St. Croix is unusually deep for Minnesota at 78 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. With 8,393 acres of surface and 124.5 miles of shoreline, Pool of Lake St. Croix is a large water by Minnesota standards — recreational pressure is spread across a long shoreline. Within Washington County's 31 graded lakes, Pool of Lake St. Croix ranks 22 — below the local median, though not at the bottom.

Eurasian watermilfoil is established at Pool of Lake St. Croix, which can dampen recreational access and pressure the native plant community. Muskie are on the species list at Pool of Lake St. Croix, alongside the lake's 36 other documented fish. The lake lacks a documented public access point, so visitor use is limited. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.