Northwood Lake
Hennepin County, MinnesotaHypereutrophic
Northwood Lake grades an F: every scored parameter (clarity and phosphorus) rates poorly, placing it among the most stressed lakes monitored in Minnesota. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.
The hypereutrophic status — TSI 91 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Northwood Lake ranks 91 of 95 in Hennepin County — at the lower end of the locally monitored distribution.
No invasive species are currently listed at Northwood Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Northwood Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The lake lacks a documented public access point, so visitor use is limited. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-09-06. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 0.5 ft of visibility. Phosphorus level: 550 µg/L. Trophic State Index: 91.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 0.5 ft | F |
| Phosphorus | 550 µg/L | F |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 91 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.304 m/yr | 5 |
Location
County Ranking
Ranked #91 of 95 lakes in Hennepin County
Cleaner Lakes Within 30 Miles
Northwood Lake holds Grade F. 5 nearby lakes hold higher grades.
- CMedicine LakeHennepin County · mi · Two grade letters higher (F → C)
- CSchmidt LakeHennepin County · mi · Two grade letters higher (F → C)
- CBass LakeHennepin County · mi · Two grade letters higher (F → C)
- CCrystal LakeHennepin County · mi · Two grade letters higher (F → C)
- DMeadow LakeHennepin County · mi · Higher grade (F → D)
Nearby Lakes in Hennepin County
More Minnesota Lake Rankings
State Parks Near Northwood Lake
Other Grade F Lakes in Minnesota
EPA Impairment Status
Northwood 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 MN27-0627-00 · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-09-06
Monitoring stations: 1