Nygren Dam Lake is a 33-acre productive, nutrient-rich eutrophic lake in Morton County, North Dakota with a maximum depth of 36 feet (13-foot average). Water quality is graded D based on 2 sampling years through 2023. Water clarity is improving over recent sampling years. The lake supports 2 documented fish species including Bluegill and Largemouth Bass. 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, North Dakota DNR, last sampled 2023-10-20. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 2.6 ft of visibility. Chlorophyll-a: 24.7 µg/L. Trophic State Index: 63.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 24.7 µg/L | D |
| Trophic State Index (TSI) | 63 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 35.5 ft |
| Average Depth | 13 ft |
| Surface Area | 33 acres |
| Shoreline Length | 0.7 mi |
| Public Access | Yes |
Where to stay near Nygren Dam Lake
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Fish Species
Click a species to see every graded lake where it is documented.
Fishing Nygren Dam Lake
Water Quality Trend: → Stable
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.09 m/yr | 2 |
| Chlorophyll-a | ↓ Declining | +21.1 µg/L/yr | 2 |
Recreation & Access
Water Temperature
Nygren Dam Lake averages about 64°F at the surface in summer, 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 →
Location
County Ranking
Ranked #1 of 4 lakes in Morton County
Cleaner Lakes Within 30 Miles
Nygren Dam Lake holds Grade D. 2 nearby lakes hold higher grades.
- CLake TschidaGrant County · 28.5 mi · Higher grade (D → C)
- CLake TschidaGrant County · 29.4 mi · Higher grade (D → C)
Nearby Lakes in Morton County
Explore Nygren Dam Lake across LakeGrade
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Species activity outlook by water temperature and season
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High nutrients, frequent algae, reduced clarity
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More records, surveys & data sources
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
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Depth, fish, and access data from North Dakota Game & Fish
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2023-10-20
Monitoring stations: 1