Lake Mendota

On the LakeGrade scale Lake Mendota grades a B, with clarity at 18.0 ft and 50 µg/L of phosphorus placing it above the Wisconsin median. High phosphorus is the leading drag on the score — likely from upland agriculture, lawn runoff, or in-lake sediment release.

Mesotrophic conditions dominate at Lake Mendota: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. Lake Mendota is unusually deep for Wisconsin at 83 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. At 9,781 acres, Lake Mendota is one of the larger lakes in Dane County, with partial shoreline records supporting multiple distinct use patterns. Within Dane County's 23 graded waters, Lake Mendota sits at rank 3, near the top of the local distribution.

Zebra mussel presence at Lake Mendota means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The fishery includes walleye alongside the lake's other 8 documented species — a notable draw for Wisconsin anglers. A documented public access point at Lake Mendota 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.