Greenfield Lake
Adair County, WisconsinEutrophic
Greenfield Lake is a 50-acre productive, nutrient-rich eutrophic lake in Adair County, IA. Water quality is graded F based on 2 sampling years through 2024. Compared to the 4 other monitored lakes in Adair County, Greenfield Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2024-09-29. 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 2.1 ft of visibility. Chlorophyll-a: 53.8 µg/L. Trophic State Index: 68.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.1 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 53.8 µg/L | F |
| Trophic State Index (TSI) | 68 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 49.6 acres |
Location
County Ranking
Ranked #3 of 5 lakes in Adair County
Cleaner Lakes Within 30 Miles
Greenfield Lake holds Grade F. 2 nearby lakes hold higher grades.
- CMormon Trail LakeAdair County · 8.9 mi · Two grade letters higher (F → C)
- DNodaway LakeAdair County · 1 mi · Higher grade (F → D)
Nearby Lakes in Adair County
More Wisconsin Lake Rankings
Other Grade F Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
Reservoir Info (USACE NID)
Greenfield Lake is a man-made reservoir impounded by the Greenfield Reservoir Dam (completed 1979), built primarily for water supply on the TR- MIDDLE NODAWAY R.; earth-type dam, 42 ft tall and 990 ft long.
- Surface area
- 49.6 ac
- Normal storage
- 612 ac-ft
- Max storage
- 1,150 ac-ft
- Drainage area
- 1.5 sq mi
- Hazard class
- High
- Owner
- Greenfield Municipal Utilities
Source: USACE National Inventory of Dams, NID ID IA02267 · Operator website
EPA Impairment Status
Greenfield 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 05-NOD-1401 · Official waterbody report · Matched by proximity (1.55 km)
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: 2024-09-29
Monitoring stations: 1