Nielson Lake
Nielson Lake in Washington County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 92.5 µg/L. Chlorophyll-a (algae): 66.5 µg/L.
- Clarity
- 1.6 ft
- Max depth
- ~24 ft est.
- Type
- Hypereutrophic
- Trend
- ↓ Declining
- Public access
- No
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Nielson Lake →
Next lake in Washington County
Nielson Lake is a highly nutrient-loaded hypereutrophic lake in Washington County, Minnesota with an estimated average depth of about 24 feet. Water quality is graded F based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 74 other monitored lakes in Washington County, Nielson Lake ranks #71 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-01. Grade methodology: LakeGrade methodology.
Watch Nielson Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Grade onlyLimited data
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.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.6 ft of visibility. Phosphorus level: 92.5 µg/L. Chlorophyll-a: 66.5 µg/L. Trophic State Index: 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 92.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 66.5 µg/L | Poor |
| Trophic State Index (TSI) | 70 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Nielson Lake
Compare lakeside cabins, hotels, and vacation rentals near Nielson Lake in Washington County, Minnesota — 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 Nielson Lake are listed below.
Top-rated places to stay near Nielson Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~24 ft est. |
| Average Depth | ~9 ft est. |
| Public Access | No |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Nielson Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Nielson Lake
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.14 m/yr | 2 |
EPA Impairment Status
Nielson Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN82-0055-00 · Official waterbody report
County Ranking
Ranked #71 of 75 lakes in Washington County
Nearby Lakes With Higher Grades
Nielson 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.
Nearby Lakes in Washington County
Frequently asked questions about Nielson Lake
What is the water quality grade for Nielson Lake?
- Nielson Lake in Washington County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 92.5 µg/L. Chlorophyll-a (algae): 66.5 µg/L.
Is Nielson Lake safe to swim in?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Nielson Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 66.5 µg/L. Always check local health department advisories before swimming.
How deep is Nielson Lake?
- No published bathymetric survey covers Nielson Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 24 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Nielson Lake across LakeGrade
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Washington County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its grade
Lakes in the St. Croix Watershed, ranked by water quality
Very high nutrients, dense algae, poor clarity
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
State Parks Near Nielson Lake
Other Grade F Lakes in Minnesota
Hypereutrophic Lakes in Minnesota
Where this data comes from
24 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA24 samples · 2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder