Rudd Lake
Floyd County, IowaView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
↑ up from B at the last regrade
- Mesotrophic
- #1 of 1 in the county
Rudd Lake in Floyd County, Iowa has a water quality grade of A (Excellent). Water clarity: 8.1 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 4.5 µg/L.
- Clarity
- 8.1 ft
- Typical in September
- 72°F
- Type
- Mesotrophic
- Trend
- ↓ Declining
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Watch Rudd Lake’s letter
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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.
Rudd Lake is a mesotrophic lake in Floyd County, Iowa. Water quality is graded A 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: LakeQuality methodology.
Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Moderate clarity, visible to about 8.1 ft. Phosphorus 14 µg/L. Chlorophyll-a 4.5 µg/L. TSI 45. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.1 ft | Not graded |
| Phosphorus | 14 µg/L | Good |
| Chlorophyll-a (Algae) | 4.5 µg/L | Good |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Water Temperature
Rudd Lake typically sits around 72°F at the surface in September. Summer average is about 77°F. 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 →
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 |
| Phosphorus | ↑ Improving | -2.7 µg/L/yr | 4 |
| Chlorophyll-a | ↓ Declining | +2.49 µg/L/yr | 4 |
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.
County Ranking
Ranked #1 of 1 lakes in Floyd County
Nearby Lakes in Floyd County
Frequently asked questions about Rudd Lake
Where is Rudd Lake?
- Rudd Lake is a lake in Floyd County, Iowa. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Rudd Lake?
- Rudd Lake in Floyd County, Iowa has a water quality grade of A (Excellent). Water clarity: 8.1 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 4.5 µg/L.
Is Rudd Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Rudd Lake?
- Rudd Lake typically sits around 72°F at the surface in September, from 23 EPA Water Quality Portal field readings (2011–2023). That is a typical value for the month, not a live reading.
Explore Rudd Lake across LakeQuality
More Iowa Lake Rankings
Other Grade A Lakes in Iowa
Mesotrophic Lakes in Iowa
Where this data comes from
66 measurements from 1 monitoring station, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX66 samples · 2021–2024
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- In-Vitro Determination of Chlorophyll
- ISU modification of APHA 2130-B
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)