Caldron Falls Reservoir

On the LakeGrade rubric, Caldron Falls Reservoir pulls an A: clarity at 17.7 ft and phosphorus readings still being added put it in the top bracket for Wisconsin. 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.

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. The lake bottoms out at 40 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. At 1,063 acres, Caldron Falls Reservoir is one of the larger lakes in Marinette County, with partial shoreline records supporting multiple distinct use patterns. Among the 22 graded lakes in Marinette County, Caldron Falls Reservoir sits at rank 9, above the county median.

Zebra mussels have been documented at Caldron Falls Reservoir, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Walleye are documented at Caldron Falls Reservoir, one of 5 fish species on record for the lake. 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.