Green Lake

Green Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season. The lake's weakest score is on Secchi depth — the water looks more turbid than its phosphorus number alone would predict.

Mesotrophic conditions dominate at Green Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. A maximum depth of 37 ft puts Green Lake in the middle of Wisconsin's depth distribution. The lake is compact at 70 acres, with partial shoreline records and little volume to buffer nutrient inputs. Within Washington County's 15 graded lakes, Green Lake ranks 8 — below the local median, though not at the bottom.

Eurasian watermilfoil has been documented at Green Lake, requiring shoreline management to keep dense mats from crowding native vegetation. 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.