Belcourt Inlet Lake
Rolette County, North DakotaView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
↑ up from D at the last regrade
- Eutrophic
- #6 of 6 in the county
Belcourt Inlet Lake in Rolette County, North Dakota has a water quality grade of B (Good). Water clarity: 3.3 ft visibility. Phosphorus: 30.5 µg/L. Chlorophyll-a (algae): 10.7 µg/L.
- Clarity
- 3.3 ft
- Typical in September
- 60°F
- Type
- Eutrophic
- Trend
- ↓ Declining
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Belcourt Inlet Lake is a productive, nutrient-rich eutrophic lake in Rolette County, North Dakota. Water quality is graded B based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. Compared to the 5 other monitored lakes in Rolette County, Belcourt Inlet Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2025-09-16. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLow algae
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.
The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: B (Good)
Very murky, less than 3.3 ft of visibility. Phosphorus 30.5 µg/L. Chlorophyll-a 10.7 µg/L. TSI 56. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.3 ft | Not graded |
| Phosphorus | 30.5 µg/L | Good |
| Chlorophyll-a (Algae) | 10.7 µg/L | Good |
| Trophic State Index (TSI) | 56 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Belcourt Inlet Lake typically sits around 60°F at the surface in September. Summer average is about 69°F. Usually warmest in Jul (about 72°F) and coldest in May (about 57°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 141 field readings (2010–2025) via the EPA Water Quality Portal. See the full Belcourt Inlet Lake water temperature breakdown →
Fishing Belcourt Inlet Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.17 m/yr | 5 |
| Phosphorus | ↓ Declining | +4.7 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +0.85 µg/L/yr | 4 |
County Ranking
Ranked #6 of 6 lakes in Rolette County
Nearby Lakes With Higher Grades
Belcourt Inlet Lake holds Grade B. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Rolette County
Frequently asked questions about Belcourt Inlet Lake
Where is Belcourt Inlet Lake?
- Belcourt Inlet Lake is a lake in Rolette County, North Dakota. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Belcourt Inlet Lake?
- Belcourt Inlet Lake in Rolette County, North Dakota has a water quality grade of B (Good). Water clarity: 3.3 ft visibility. Phosphorus: 30.5 µg/L. Chlorophyll-a (algae): 10.7 µg/L.
Is Belcourt Inlet Lake safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Belcourt Inlet Lake?
- Belcourt Inlet Lake typically sits around 60°F at the surface in September, from 141 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
Explore Belcourt Inlet Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at North Dakota's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
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Other Grade B Lakes in North Dakota
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Where this data comes from
212 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Turtle Mountain Environmental Office (Tribal)
TURTLEMT212 samples · 2020–2025
Analytical methods
- 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.