Slipbluff Lake is a 18-acre mesotrophic lake in Decatur County, Iowa. Water quality is graded B based on 2 sampling years through 2024. Water clarity is improving over recent sampling years. Compared to the 2 other monitored lakes in Decatur County, Slipbluff Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-15. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Moderate clarity, visible to about 9 ft. Chlorophyll-a: 4.5 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9 ft | C |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 4.5 µg/L | A |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 18 acres |
Where to stay near Slipbluff Lake
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Fishing Slipbluff Lake
Water Quality Trend: → Stable
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.433 m/yr | 4 |
| Chlorophyll-a | ↓ Declining | +0.25 µg/L/yr | 4 |
Water Temperature
Slipbluff Lake averages about 79°F at the surface in summer, usually warmest in Jul (about 83°F) and coldest in May (about 71°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 26 field readings (2010–2023) via the EPA Water Quality Portal. See the full Slipbluff Lake water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Slipbluff Lake, reaching a maximum surveyed depth of 21 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #2 of 3 lakes in Decatur County
Cleaner Lakes Within 30 Miles
Slipbluff Lake holds Grade B. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Decatur County
Explore Slipbluff Lake across LakeGrade
More Iowa Lake Rankings
Other Grade B Lakes in Iowa
Mesotrophic Lakes in Iowa
More records, surveys & data sources
Reservoir Info (USACE NID)
Slipbluff Lake is a man-made reservoir impounded by the Slip Bluff Park Dam (completed 1970), built primarily for recreation on the TR-POTTEROFF CREEK; earth-type dam, 33 ft tall and 333 ft long.
- Surface area
- 18 ac
- Normal storage
- 230 ac-ft
- Max storage
- 464 ac-ft
- Drainage area
- 0.44 sq mi
- Hazard class
- Low
- Owner
- Decatur County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA00349 · Operator website · Matched by proximity (1 km)
Regulated Pollution Sources Nearby
5 EPA-permitted facilities operate within about 5 miles of Slipbluff Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Davis City, City Of Stp (Sirwa)Davis City · 2.9 mi away · NPDES IA0060232Recent violation
- Iowa Dot Rest Area #34 I35 LamoniLamoni · 0.2 mi away · NPDES IA0068934
- Procom, Inc.Lamoni · 2.2 mi away · NPDES IA0068144
- Chief Lamoni Motel-StpLamoni · 3.1 mi away · NPDES IA0069051
- Lamoni Industrial Park StpLamoni · 3.4 mi away · NPDES IA0070963
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
Most recent sample: 2024-09-15
Monitoring stations: 1