Mchugh Slough Lake is a highly nutrient-loaded hypereutrophic lake in Nelson County, North Dakota. Water quality is graded F based on 3 sampling years through 2023. Overall water quality is improving over recent sampling years. Compared to the 8 other monitored lakes in Nelson County, Mchugh Slough Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, North Dakota DNR, last sampled 2023-10-16. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.6 ft of visibility. Phosphorus level: 388.5 µg/L. Chlorophyll-a: 88.7 µg/L. Trophic State Index: 78.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | F |
| Phosphorus | 388.5 µg/L | F |
| Chlorophyll-a (Algae) | 88.7 µg/L | F |
| Trophic State Index (TSI) | 78 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Mchugh Slough Lake
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Fishing Mchugh Slough Lake
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +8.55 m/yr | 4 |
| Phosphorus | ↓ Declining | +95.93 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -27.7 µg/L/yr | 4 |
Water Temperature
Mchugh Slough Lake averages about 70°F at the surface in summer, usually warmest in Jul (about 73°F) and coldest in Feb (about 35°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 295 field readings (2010–2023) via the EPA Water Quality Portal. See the full Mchugh Slough Lake water temperature breakdown →
Location
County Ranking
Ranked #9 of 9 lakes in Nelson County
Cleaner Lakes Within 30 Miles
Mchugh Slough Lake holds Grade F. 5 nearby lakes hold higher grades.
- CEast Devils LakeRamsey County · 20.9 mi · Two grade letters higher (F → C)
- DWest Stump LakeNelson County · 15.7 mi · Higher grade (F → D)
- DEast Stump LakeNelson County · 16.9 mi · Higher grade (F → D)
- DLake LarettaNelson County · 4.4 mi · Higher grade (F → D)
- FWestern Stump LakeNelson County · 14.3 mi · Higher overall water quality score
Nearby Lakes in Nelson County
Explore Mchugh Slough Lake across LakeGrade
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Species activity outlook by water temperature and season
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Very high nutrients, dense algae, poor clarity
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Other Grade F Lakes in North Dakota
Hypereutrophic Lakes in North Dakota
More records, surveys & data sources
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2023-10-16
Monitoring stations: 1