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LakeQuality
B

Big Traverse Bay Lake

Lake of the Woods County, MinnesotaMesotrophic

Big Traverse Bay Lake comes in at a B on the grading rubric — a respectable showing for a Minnesota lake of its size and depth. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

Mesotrophic conditions dominate at Big Traverse Bay Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Big Traverse Bay Lake sits at rank 8 of 11 in Lake of the Woods County, in the lower half of the local distribution.

Zebra mussels have been documented at Big Traverse Bay Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. The state fisheries records do not list documented species for Big Traverse Bay Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Public access is available — the lake is on the Minnesota PCA public-access list. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-08-28. Grade methodology: LakeGrade methodology.

Swimming Safety

Good for swimming, clear water with low algae levels

Water Quality Grade: B, Good

Good clarity, visible to about 13.1 ft. Phosphorus level: 33.5 µg/L. Trophic State Index: 47.

MetricValueGrade
Water Clarity (Secchi Depth)13.1 ftB
Phosphorus33.5 µg/LC
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)47Mesotrophic

Moderate nutrients, good water quality

Invasive Species

spiny waterfleazebra mussel

Water Quality Trend: Declining

Based on 6 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Declining-0.183 m/yr6
Phosphorus Declining+1.29 µg/L/yr5

Ice Season

Historical ice data from Minnesota DNR (6 observations).

Typical Ice-Out
May 5
EarliestLatest
Ice-Out1976-04-26 (1976)1996-05-19 (1996)
Ice-In1986-11-11 (1986)1988-11-17 (1988)

Most recent ice-out: 1997-05-06

Location

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County Ranking

Ranked #8 of 11 lakes in Lake of the Woods County

Nearby Lakes in Lake of the Woods County

DNR Reports & Resources

Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Big Traverse Bay Lake. 1 report on file.

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Ice data from Minnesota DNR Climate

Most recent sample: 2025-08-28

Monitoring stations: 1