Grays Lake
Polk County, WisconsinEutrophic
Grays Lake is a productive, nutrient-rich eutrophic lake in Polk County, IA. Water quality is graded F based on 2 sampling years through 2024. Compared to the 11 other monitored lakes in Polk County, Grays Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2024-09-18. Grade methodology: LakeGrade methodology.
Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.6 ft of visibility. Chlorophyll-a: 46.5 µg/L. Trophic State Index: 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 46.5 µg/L | F |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Location
County Ranking
Ranked #6 of 12 lakes in Polk County
Cleaner Lakes Within 30 Miles
Grays Lake holds Grade F. 5 nearby lakes hold higher grades.
- ATerra Park LakePolk County · 7.2 mi · Two grade letters higher (F → A)
- BDale Maffitt ReservoirDallas County · 8.7 mi · Two grade letters higher (F → B)
- CLake PetockaPolk County · 13.9 mi · Two grade letters higher (F → C)
- DThomas Mitchell LakePolk County · 14.2 mi · Higher grade (F → D)
- DEaster LakePolk County · 4.6 mi · Higher grade (F → D)
Nearby Lakes in Polk County
More Wisconsin Lake Rankings
Other Grade F Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
EPA Impairment Status
Grays 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 IA 04-RAC-1118 · 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: 2024-09-18
Monitoring stations: 1