Harpt Lake

On the LakeGrade scale Harpt Lake grades a B, with clarity at 12.3 ft and 44 µg/L of phosphorus placing it above the Wisconsin median. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

A TSI near 50 places Harpt Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. The lake's 54 ft maximum depth is in the upper tier for Wisconsin — deep enough for cold-water fish to find refuge in summer. The lake is compact at 32 acres, with partial shoreline records and little volume to buffer nutrient inputs. Within Manitowoc County's 18 graded lakes, Harpt Lake ranks 13 — below the local median, though not at the bottom.

Harpt Lake carries an invasive watermilfoil record — boat-launch decontamination and shoreline care matter more here than at uninfested lakes. The fishery includes walleye alongside the lake's other 4 documented species — a notable draw for Wisconsin anglers. A documented public access point at Harpt Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.