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LakeQuality

Bright Lake

F
Grade F — Algae-prone
Algae-prone · #11 of 12 lakes in the county · 1 ft clear · Hypereutrophic · 639 acres
Limited DataHypereutrophic

Bright Lake in Martin County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1 ft visibility. Phosphorus: 110.5 µg/L. Chlorophyll-a (algae): 54.1 µg/L. Maximum depth: 7 ft. Surface area: 638.55 acres.

Clarity
1 ft
Typical in August
79°F
Max depth
7 ft
Area
639 acres
Type
Hypereutrophic
Public access
Yes
Ice-out
Mar 20
Open water
256 days

Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Bright Lake

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FClear Lake1 ft clear · Martin CountyView →
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Bright Lake is a 639-acre highly nutrient-loaded hypereutrophic lake in Martin County, Minnesota with a maximum depth of 7 feet. Water quality is graded F based on 2 sampling years through 2025. The lake supports 20 documented fish species including bigmouth buffalo, black bullhead, and black crappie. Public access is available with 1 public boat landing. Compared to the 11 other monitored lakes in Martin County, Bright Lake ranks #11 for water quality.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-16. Grade methodology: LakeGrade methodology.

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Swimming Safety

Grade only

Limited data

Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.

Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom

Compare the safest swimming lakes near Mankato

Get alerts for Bright Lake

Water Quality Grade: F (Algae-prone)

Very murky, less than 1 ft of visibility. Phosphorus level: 110.5 µg/L. Chlorophyll-a: 54.1 µg/L. Trophic State Index: 73.

MetricValueGrade
Water Clarity (Secchi Depth)1 ftNot graded
Phosphorus110.5 µg/LPoor
Chlorophyll-a (Algae)54.1 µg/LPoor
Trophic State Index (TSI)73Hypereutrophic

Very high nutrients, dense algae, poor clarity

Where to stay near Bright Lake

Compare lakeside cabins, hotels, and vacation rentals near Bright Lake in Martin County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Bright Lake are listed below.

Top-rated places to stay near Bright Lake

Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.

Planning a whole trip? See where to stay at Minnesota’s top lakes →

Water Temperature

Bright Lake typically sits around 79°F at the surface in August. Summer average is about 79°F. Usually warmest in Jul (about 81°F) and coldest in May (about 53°F). These are typical values by month — not a live reading.

Jan
Feb
Mar
Apr
May
53°
Jun
76°
Jul
81°
Aug
79°
Sep
74°
Oct
Nov
Dec

Typical surface water temperature by month, from 13 field readings (20252025) via the EPA Water Quality Portal. See the full Bright Lake water temperature breakdown →

Lake Details

CharacteristicValue
Maximum Depth7 ft
Surface Area639 acres
Shoreline Length4.6 mi
Littoral Zone102%
Public AccessYes

Lake Size & Watershed

Watershed (drainage) area
21 sq mi
Elevation
1,220 ft

Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).

Recreation & Access

1
Boat Landings
Yes
Public Access
  • Bright LakePublic

Fish Species

Click a species to see every graded lake where it is documented.

Fishing Bright Lake

Ice Season

Historical ice data from Minnesota DNR (14 observations).

Typical Ice-Out
Mar 20
Typical Ice-In
Dec 1

Estimated open water season: 256 days

EarliestLatest
Ice-Out2024-02-23 (2024)2023-04-11 (2023)
Ice-In2022-11-18 (2022)2021-12-07 (2021)

Most recent ice-out: 2026-03-09

EPA Impairment Status

Bright Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

Impaired biota (cause unknown)Nutrients (phosphorus, nitrogen)

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit MN46-0052-00 · Official waterbody report

County Ranking

Ranked #11 of 12 lakes in Martin County

Nearby Lakes in Martin County

Frequently asked questions about Bright Lake

What is the water quality grade for Bright Lake?

Bright Lake in Martin County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1 ft visibility. Phosphorus: 110.5 µg/L. Chlorophyll-a (algae): 54.1 µg/L. Maximum depth: 7 ft. Surface area: 638.55 acres.

Is Bright Lake safe to swim in?

Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Bright Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 54.1 µg/L. Always check local health department advisories before swimming.

What is the water temperature of Bright Lake?

Bright Lake typically sits around 79°F at the surface in August, from 13 EPA Water Quality Portal field readings (2025–2025). That is a typical value for the month, not a live reading.

How deep is Bright Lake?

Bright Lake has a maximum depth of 7 feet. The lake covers 638.55 acres.

What fish are in Bright Lake?

Fish species found in Bright Lake include bigmouth buffalo, black bullhead, black crappie, channel catfish, common carp, freshwater drum, gizzard shad, green sunfish, largemouth bass, northern pike, orangespotted sunfish, quillback, shorthead redhorse, smallmouth buffalo, walleye, white bass, white crappie, white sucker, yellow bullhead, yellow perch. Bright Lake is located in Martin County, Minnesota.

When does Bright Lake thaw?

Bright Lake typically has ice-out around Mar 20. Ice typically forms around Dec 1. The open water season is approximately 256 days.

Are there boat ramps on Bright Lake?

Bright Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Bright Lake. Public access is listed as yes.

Hypereutrophic Lakes in Minnesota

Where this data comes from

15 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.

Collected and reported by

  • Minnesota Pollution Control Agency - Ambient Surface WaterMNPCA15 samples · 2025

Analytical methods

  • Field measurement/observation, generic method
  • Phosphorus by Colorimetry
  • 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)

Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.

Other records on this page

Impairment status from EPA ATTAINS 303(d) database

Lake size & watershed from HydroLAKES (HydroSHEDS)

Lake details from Minnesota DNR LakeFinder

Named boat-access points from the USGS National Boat Ramps inventory

Ice data from Minnesota DNR Climate