Nelson Lake is a 660-acre productive, nutrient-rich eutrophic lake in Oliver County, North Dakota with a maximum depth of 33 feet (14-foot average). Water quality is graded D based on 2 sampling years through 2023. The lake supports 5 documented fish species including Bluegill, Largemouth Bass, and Black Crappie. Public access is available with 2 public boat landings. Compared to the 2 other monitored lakes in Oliver County, Nelson Lake ranks #3 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
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 1.3 ft of visibility. Chlorophyll-a: 23.1 µg/L. Trophic State Index: 67.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.3 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 23.1 µg/L | D |
| Trophic State Index (TSI) | 67 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 33.4 ft |
| Average Depth | 14.4 ft |
| Surface Area | 660 acres |
| Shoreline Length | 12.5 mi |
| Public Access | Yes |
Where to stay near Nelson Lake
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Fish Species
Click a species to see every graded lake where it is documented.
Fishing Nelson Lake
Recreation & Access
Water Temperature
Nelson Lake averages about 79°F at the surface in summer, usually warmest in Jul (about 82°F) and coldest in Oct (about 60°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 14 field readings (2023–2023) via the EPA Water Quality Portal. See the full Nelson Lake water temperature breakdown →
Location
County Ranking
Ranked #3 of 3 lakes in Oliver County
Cleaner Lakes Within 30 Miles
Nelson Lake holds Grade D. 2 nearby lakes hold higher grades.
- BArroda LakeOliver County · 11.6 mi · Two grade letters higher (D → B)
- CEast Arroda LakeOliver County · 11.7 mi · Higher grade (D → C)
Nearby Lakes in Oliver County
Explore Nelson Lake across LakeGrade
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Fish species and best lakes in Oliver County
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
Eutrophic Lakes in North Dakota
More records, surveys & data sources
Reservoir Info (USACE NID)
Nelson Lake is a man-made reservoir impounded by the Nelson Lake Dam (completed 1967), built primarily for other on the Square Butte Creek; earth-type dam, 66 ft tall and 2,200 ft long.
- Surface area
- 660 ac
- Normal storage
- 10,350 ac-ft
- Max storage
- 20,122 ac-ft
- Drainage area
- 146 sq mi
- Hazard class
- High
- Owner
- Minnkota Power Coop
All listed purposes: Other;Recreation.
Source: USACE National Inventory of Dams, NID ID ND00096 · Operator website
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
4 EPA-permitted facilities operate within about 5 miles of Nelson Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 4 facilities have a reported Clean Water Act violation in the past three years.
- Minnkota Power CooperativeCenter · 0.2 mi away · NPDES ND0000370MajorRecent violation
- Minnesota PowerCenter · 0.7 mi away · NPDES ND0026361Recent violation
- Bni Coal Ltd CenterCenter · 1.2 mi away · NPDES ND0024601Recent violation
- Center Coal CoCenter · 1.4 mi away · NPDES ND0025321Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
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: 2023-10-16
Monitoring stations: 1