Sweetbriar Dam Lake
Morton County, North DakotaView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- #2 of 4 in the county
- Public access
Sweetbriar Dam Lake in Morton County, North Dakota has a water quality grade of F (Algae-prone). Water clarity: 3 ft visibility. Phosphorus: 353 µg/L. Chlorophyll-a (algae): 54 µg/L.
- Clarity
- 3 ft
- Type
- Hypereutrophic
- Phosphorus
- 353 µg/L
- Chlorophyll-a
- 54 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Stays near Sweetbriar Dam Lake
Compare lakeside cabins, hotels, and vacation rentals near Sweetbriar Dam Lake in Morton County, North Dakota — 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 Sweetbriar Dam Lake are listed below.
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Sweetbriar Dam Lake is a highly nutrient-loaded hypereutrophic lake in Morton County, North Dakota. Water quality is graded F based on 3 sampling years through 2024. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 3 other monitored lakes in Morton County, Sweetbriar Dam Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2024-08-06. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyAlgae risk
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 F is nutrients and algae, not a swimming clearance. Sweetbriar Dam Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 3 ft of visibility. Phosphorus 353 µg/L. Chlorophyll-a 54 µg/L. TSI 73. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3 ft | Not graded |
| Phosphorus | 353 µg/L | Poor |
| Chlorophyll-a (Algae) | 54 µg/L | Poor |
| Trophic State Index (TSI) | 73 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Fishing Sweetbriar Dam Lake
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.32 m/yr | 2 |
| Phosphorus | ↓ Declining | +62.5 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -29.3 µg/L/yr | 3 |
EPA Impairment Status
Sweetbriar Dam Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit ND-10130203-005-L_00 · Official waterbody report · Matched by proximity (0.16 km)
County Ranking
Ranked #2 of 4 lakes in Morton County
Nearby Lakes With Higher Grades
Sweetbriar Dam Lake holds Grade F. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Morton County
Frequently asked questions about Sweetbriar Dam Lake
Where is Sweetbriar Dam Lake?
- Sweetbriar Dam Lake is a lake in Morton County, North Dakota. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Sweetbriar Dam Lake?
- Sweetbriar Dam Lake in Morton County, North Dakota has a water quality grade of F (Algae-prone). Water clarity: 3 ft visibility. Phosphorus: 353 µg/L. Chlorophyll-a (algae): 54 µg/L.
Is Sweetbriar Dam Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Sweetbriar Dam Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Explore Sweetbriar Dam Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at North Dakota's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
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Where this data comes from
109 measurements from 2 monitoring stations, 2022–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Dakota Department Of Environmental Quality
21NDHDWQ_WQX109 samples · 2022–2024
Analytical methods
- Phosphorus by Colorimetry
- 447.0 ~ EPA; Chlorophyll a and b in phytoplankton by HPLC/UV
- 4500 NO3 E ~ Nitrate in Water- Cadmium Reduction
- Turbidity by Nephelometry
Monitoring station identifiers (2)
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