Diamond Lake
Poweshiek County, WisconsinEutrophic
Diamond Lake is a 93-acre productive, nutrient-rich eutrophic lake in Poweshiek County, IA. Water quality is graded F based on 2 sampling years through 2024. Compared to the 1 other monitored lakes in Poweshiek County, Diamond Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2024-08-28. 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: 44.6 µg/L. Trophic State Index: 69.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 44.6 µg/L | F |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 93 acres |
Location
County Ranking
Ranked #1 of 2 lakes in Poweshiek County
Cleaner Lakes Within 30 Miles
Diamond Lake holds Grade F. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Poweshiek County
More Wisconsin Lake Rankings
Other Grade F Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
Reservoir Info (USACE NID)
Diamond Lake is a man-made reservoir impounded by the Diamond Lake Dam (Poweshiek Co) (completed 1952), built primarily for water supply on the TR-MOON CREEK; earth-type dam, 40 ft tall and 900 ft long.
- Surface area
- 93 ac
- Normal storage
- 780 ac-ft
- Max storage
- 1,100 ac-ft
- Drainage area
- 4.42 sq mi
- Hazard class
- Significant
- Owner
- Montezuma Water Works
All listed purposes: Water Supply;Recreation.
Source: USACE National Inventory of Dams, NID ID IA01368 · Operator website · Matched by proximity (0.21 km)
EPA Impairment Status
Diamond 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 03-NSK-861 · 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: 2024-08-28
Monitoring stations: 1