Collins Lake

Collins Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Portage County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

Mesotrophic conditions dominate at Collins Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. Collins Lake is unusually deep for Wisconsin at 56 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. The lake is compact at 43 acres, with partial shoreline records and little volume to buffer nutrient inputs. Within Portage County's 29 graded lakes, Collins Lake ranks 21 — below the local median, though not at the bottom.

Collins 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. Public access is available — the lake is on the Wisconsin DNR public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.