Union Lake

The LakeGrade rubric puts Union Lake at a C: clarity at 3.0 ft, 1 µg/L of phosphorus, and a TSI of 35 signal an intermediate trophic state. Clarity is the limiting factor — phosphorus is reasonable but suspended particles or algal cells keep water transparency below Minnesota norms.

A TSI value of 35 puts Union Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. A maximum depth of just 10 ft means sediment-bound phosphorus releases back into the water column whenever wind stirs the bottom — a classic shallow-lake dynamic. The lake's 397 acres and 5.2 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Within Rice County's 12 graded waters, Union Lake sits at rank 2, near the top of the local distribution.

No invasive species are currently listed at Union Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Union Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. A documented public access point at Union Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Ice-out has been recorded 12 times at Union Lake, with a median around Mar 23. 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.