Is Greenwich L. Lake safe to swim in?

Good for swimming, clear water with low algae levels. Greenwich L. Lake has an overall water quality grade of B. Always check local health department advisories before swimming.

Thunder Bay District County, Ontario · Water Quality Report Card

Greenwich L. Lake

Grade B — Good

Oligotrophic

Greenwich L. Lake in Thunder Bay District, Ontario received a water quality grade of B (Good). Water clarity: 2.3 m visibility. Phosphorus: 4.2 µg/L.

Clarity: 2.3 m
Type: Oligotrophic

Where to stay →Safe to swim?

Greenwich L. Lake is a cold, clear oligotrophic lake in Thunder Bay District County, Ontario. Water quality is graded B based on 2 sampling years through 2025. Compared to the 301 other monitored lakes in Thunder Bay District County, Greenwich L. Lake ranks #162 for water quality.

Source: EPA Water Quality Portal sampling records, Ontario MECP, last sampled 2025-08-01. Grade methodology: LakeGrade methodology.

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Swimming Safety

Good for swimming, clear water with low algae levels

Water Quality Grade: B, Good

Moderate clarity, visible to about 7.5 ft. Phosphorus level: 4.2 µg/L. Trophic State Index: 36.

Metric	Value	Grade
Water Clarity (Secchi Depth)	2.3 m	C
Phosphorus	4.2 µg/L	A
Chlorophyll-a (Algae)	No data
Trophic State Index (TSI)	36	Oligotrophic

Low nutrients, clear water, excellent for swimming

Where to stay near Greenwich L. Lake

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Fishing Greenwich L. Lake

→ Greenwich L. Lake fishing regulations (limits, seasons, special rules)

Location

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County Ranking

Ranked #162 of 302 lakes in Thunder Bay District

Cleaner Lakes Within 30 Miles

Greenwich L. Lake holds Grade B. 2 nearby lakes hold higher grades.

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Nearby Lakes in Thunder Bay District

Explore Greenwich L. Lake across LakeGrade

Lake Fishing Forecast

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Oligotrophic Lakes

Low nutrients, clear water, excellent for swimming

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Other Grade B Lakes in Ontario

Pyramid Lake

Kenora District · 2.3 m

Savoy Lake

Kenora District · 2.2 m

Mercutio Lake

Rainy River District · 2 m

Mattawa Lake

Kenora District · 2.7 m

Scotch Lake

Kenora District · 2.8 m

Farley Lake

Rainy River District · 1.1 m

Oligotrophic Lakes in Ontario

Crooked Pine Lake Nydia Lake Eva Lake Scotch Lake

More records, surveys & data sources

Where this data comes from

Measurements for Greenwich L. Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.

Data Sources

Water quality data from the EPA Water Quality Portal

Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion

Most recent sample: 2025-08-01

Monitoring stations:

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