Yankton Lake

Yankton Lake earns an F: 94 µg/L of phosphorus and clarity at 0.8 ft signal heavy nutrient loading from the surrounding watershed. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

The hypereutrophic status — TSI 75 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. A maximum depth of just 8 ft means sediment-bound phosphorus releases back into the water column whenever wind stirs the bottom — a classic shallow-lake dynamic. Yankton Lake covers 403 acres alongside 4.9 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Yankton Lake ranks 6 of 6 in Lyon County — at the lower end of the locally monitored distribution.

Yankton Lake has no invasive species recorded in Minnesota state databases as of 2025, though prevention practices still apply at all access points. Walleye are documented at Yankton Lake, one of 15 fish species on record for the lake. A documented public access point at Yankton Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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.