Stolley Pit Lake is a productive, nutrient-rich eutrophic lake in Clay County, Iowa. Water quality is graded D based on 2 sampling years through 2024. Water clarity is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-09. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 2.7 ft of visibility. Chlorophyll-a: 17.3 µg/L. Trophic State Index: 61.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.7 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 17.3 µg/L | C |
| Trophic State Index (TSI) | 61 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Stolley Pit Lake
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Fishing Stolley Pit Lake
Water Quality Trend: → Stable
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.36 m/yr | 2 |
| Chlorophyll-a | ↑ Improving | -9.1 µg/L/yr | 2 |
Recreation & Access
Location & Depth Map
Free interactive depth-contour map of Stolley Pit Lake, reaching a maximum surveyed depth of 12 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #1 of 1 lakes in Clay County
Cleaner Lakes Within 30 Miles
Stolley Pit Lake holds Grade D. 2 nearby lakes hold higher grades.
- AWest Okoboji LakeDickinson County · 15.6 mi · Two grade letters higher (D → A)
- CUpper Gar LakeDickinson County · 15.3 mi · Higher grade (D → C)
Nearby Lakes in Clay County
Explore Stolley Pit Lake across LakeGrade
More Iowa Lake Rankings
Other Grade D Lakes in Iowa
Eutrophic Lakes in Iowa
More records, surveys & data sources
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Stolley Pit Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 2 facilities have a reported Clean Water Act violation in the past three years.
- Spencer, City Of StpSpencer · 3.6 mi away · NPDES IA0021059MajorRecent violation
- Corn Belt Power Cooperative-Wisdom StationSpencer · 3.4 mi away · NPDES IA0004570Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-09-09
Monitoring stations: 1