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F

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.

Reviewed by LakeQuality Editorial Team · Updated

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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.

MetricValueGrade
Water Clarity (Secchi Depth)0.5 ftF
Phosphorus550 µg/LF
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)91Hypereutrophic

Very high nutrients, dense algae, poor clarity

Water Quality Trend: Improving

Based on 5 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Improving+0.304 m/yr5
See year-by-year chart →

Location

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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.

See full comparison →

Nearby Lakes in Hennepin County

State Parks Near Northwood Lake

Hypereutrophic 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

Nutrients (phosphorus, nitrogen)

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