Nygren Dam Lake
Morton County, North Dakota33 acresView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- #1 of 4 in the county
- Public access
Nygren Dam Lake in Morton County, North Dakota has a water quality grade of D (Nutrient-rich). Water clarity: 2.6 ft visibility. Phosphorus: 73 µg/L. Chlorophyll-a (algae): 24.7 µg/L. Surface area: 33.1 acres.
- Clarity
- 2.6 ft
- Typical in August
- 64°F
- Area
- 33 acres
- Type
- Eutrophic
- Phosphorus
- 73 µg/L
- Chlorophyll-a
- 24.7 µg/L
- Trend
- ↓ Declining
- Public access
- Yes
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Stays near Nygren Dam Lake
Compare lakeside cabins, hotels, and vacation rentals near Nygren 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 Nygren Dam Lake are listed below.
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Nygren Dam Lake is a 33-acre productive, nutrient-rich eutrophic lake in Morton County, North Dakota. Water quality is graded D based on 3 sampling years through 2023. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 3 other monitored lakes in Morton County, Nygren Dam Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, NDDEQ, last sampled 2023-10-20. Grade methodology: LakeQuality methodology.
What Nygren Dam Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
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 D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 2.6 ft of visibility. Phosphorus 73 µg/L. Chlorophyll-a 24.7 µg/L. TSI 64. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | Not graded |
| Phosphorus | 73 µg/L | Fair |
| Chlorophyll-a (Algae) | 24.7 µg/L | Poor |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Nygren Dam Lake typically sits around 64°F at the surface in August. Summer average is about 64°F. Usually warmest in Jul (about 64°F) and coldest in Oct (about 46°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 30 field readings (2011–2023) via the EPA Water Quality Portal. See the full Nygren Dam Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 33 acres |
| Public Access | Yes |
No bathymetric survey has been published for Nygren Dam Lake, so its depth is not documented here.
Recreation & Access
- Nygren DamPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Nygren Dam Lake
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.09 m/yr | 2 |
| Phosphorus | ↓ Declining | +32.5 µg/L/yr | 2 |
| Chlorophyll-a | ↓ Declining | +21.1 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Nygren Dam Lake is a man-made reservoir impounded by the Nygren Dam (completed 1967), built primarily for recreation on the Heart River-TR; earth-type dam, 37 ft tall and 250 ft long.
- Surface area
- 33.1 ac
- Normal storage
- 92.3 ac-ft
- Max storage
- 193 ac-ft
- Drainage area
- 4 sq mi
- Hazard class
- Low
- Owner
- Morton County WRB & Hwy D
Source: USACE National Inventory of Dams, NID ID ND00200 · Operator website
County Ranking
Ranked #1 of 4 lakes in Morton County
Nearby Lakes With Higher Grades
Nygren Dam Lake holds Grade D. 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 Nygren Dam Lake
Where is Nygren Dam Lake?
- Nygren Dam Lake is a lake in Morton County, North Dakota. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Nygren Dam Lake?
- Nygren Dam Lake in Morton County, North Dakota has a water quality grade of D (Nutrient-rich). Water clarity: 2.6 ft visibility. Phosphorus: 73 µg/L. Chlorophyll-a (algae): 24.7 µg/L. Surface area: 33.1 acres.
Is Nygren Dam Lake safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Nygren Dam Lake?
- Nygren Dam Lake typically sits around 64°F at the surface in August, from 30 EPA Water Quality Portal field readings (2011–2023). That is a typical value for the month, not a live reading.
Are there boat ramps on Nygren Dam Lake?
- Nygren Dam Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Nygren Dam. Public access is listed as yes.
Explore Nygren 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
High nutrients, frequent algae, reduced clarity
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Other Grade D Lakes in North Dakota
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Where this data comes from
50 measurements from 1 monitoring station, 2022–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Dakota Department Of Environmental Quality
21NDHDWQ_WQX50 samples · 2022–2023
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
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
Depth, fish, and access data from North Dakota Game & Fish
Named boat-access points from the USGS National Boat Ramps inventory