Rudd Lake is a mesotrophic lake in Floyd County, Iowa. Water quality is graded B based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-22. 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 8.1 ft. Chlorophyll-a: 4.5 µg/L. Trophic State Index: 46.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.1 ft | C |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 4.5 µg/L | A |
| Trophic State Index (TSI) | 46 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Rudd Lake
Compare lakeside cabins, hotels, and vacation rentals near Rudd Lake in Floyd County, Iowa — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
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Fishing Rudd Lake
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.159 m/yr | 4 |
| Chlorophyll-a | ↓ Declining | +2.49 µg/L/yr | 4 |
Water Temperature
Rudd Lake averages about 77°F at the surface in summer, usually warmest in Jul (about 81°F) and coldest in Sep (about 72°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 23 field readings (2011–2023) via the EPA Water Quality Portal. See the full Rudd Lake water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Rudd Lake, reaching a maximum surveyed depth of 18 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #1 of 1 lakes in Floyd County
Cleaner Lakes Within 30 Miles
Rudd Lake holds Grade B. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Floyd County
Explore Rudd Lake across LakeGrade
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Other Grade B Lakes in Iowa
Mesotrophic Lakes in Iowa
More records, surveys & data sources
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Rudd Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Rudd City Of StpRudd · 1.3 mi away · NPDES IA0061344Recent 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
Most recent sample: 2024-10-22
Monitoring stations: 1