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B

Long Lake

Todd County, MinnesotaLimited DataOligotrophic

Long Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season.

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'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. Long Lake ranks 6 of 17 in Todd County — solidly in the upper half of the local distribution.

Long Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Long Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. A documented public access point at Long Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Ice-out has been logged at Long Lake more than two dozen times, putting the median around Apr 13 — a useful baseline for tracking climate trends. 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 2024-08-13. Grade methodology: LakeGrade methodology.

Reviewed by LakeQuality Editorial Team · Updated

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Swimming Safety

Good for swimming, clear water with low algae levels

Water Quality Grade: B, Good

Good clarity, visible to about 14 ft. Trophic State Index: 39.

MetricValueGrade
Water Clarity (Secchi Depth)14 ftB
PhosphorusNo data
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)39Oligotrophic

Low nutrients, clear water, excellent for swimming

Water Quality Trend: Stable

Based on 5 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Stable+0.07 m/yr5
See year-by-year chart →

Ice Season

Historical ice data from Minnesota DNR (64 observations).

Typical Ice-Out
Apr 13
Typical Ice-In
Nov 28

Estimated open water season: 229 days

EarliestLatest
Ice-Out2024-03-12 (2024)2018-05-02 (2018)
Ice-In2018-11-13 (2018)2015-12-19 (2015)

Most recent ice-out: 2024-03-12

Location

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County Ranking

Ranked #6 of 17 lakes in Todd County

Cleaner Lakes Within 30 Miles

Long Lake holds Grade B. One nearby lake has a higher grade.

Nearby Lakes in Todd County

DNR Reports & Resources

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

EPA Impairment Status

Long 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)MercuryNutrients (phosphorus, nitrogen)

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

Source: EPA ATTAINS assessment unit MN77-0150-02 · Official waterbody report · Matched by proximity (2.96 km)

Data Sources

Water quality data from the EPA Water Quality Portal

Impairment status from EPA ATTAINS 303(d) database

Grading methodology based on Metropolitan Council standards

Ice data from Minnesota DNR Climate

Most recent sample: 2024-08-13

Monitoring stations: 2