Rathbun Lake is a 11,013-acre productive, nutrient-rich eutrophic lake in Appanoose County, Iowa. Water quality is graded D based on 2 sampling years through 2024. Water clarity is improving over recent sampling years. Limited fish-species data available. Public access is available with 6 public boat landings.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-17. Grade methodology: LakeGrade methodology.
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Rathbun Lake Water Quality Report Card (2026)
A printable one-page report card for Rathbun Lake: grade, clarity, phosphorus, algae, multi-year trend, depth, and fish — with sources.
Swimming Safety
Based on E. coli testing, Rathbun Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 6 samples across 2 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Iowa’s current beach and health-department advisories before swimming.
Water Quality Grade: D, Poor
Very murky, less than 3 ft of visibility. Chlorophyll-a: 15.3 µg/L. Trophic State Index: 59.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 15.3 µg/L | C |
| Trophic State Index (TSI) | 59 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 11,013 acres |
| Public Access | Yes |
Where to stay near Rathbun Lake
Compare lakeside cabins, hotels, and vacation rentals near Rathbun Lake in Appanoose 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 Rathbun Lake
Water Quality Trend: → Stable
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.064 m/yr | 4 |
| Chlorophyll-a | ↓ Declining | +3.62 µg/L/yr | 4 |
Recreation & Access
Current Conditions
Latest reading Jul 6, 2026, 4:45 AM from USGS gauge 06903880. See live data ↗ — readings update every 15–60 minutes; this page refreshes on each build.
Water Temperature
Rathbun Lake averages about 76°F at the surface in summer, usually warmest in Jul (about 79°F) and coldest in May (about 64°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 Rathbun Lake water temperature breakdown →
Location
County Ranking
Ranked #1 of 1 lakes in Appanoose County
Cleaner Lakes Within 30 Miles
Rathbun Lake holds Grade D. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Appanoose County
Explore Rathbun Lake across LakeGrade
More Iowa Lake Rankings
Other Grade D Lakes in Iowa
Eutrophic Lakes in Iowa
More records, surveys & data sources
Reservoir Info (USACE NID)
Rathbun Lake is a man-made reservoir impounded by the Rathbun Dam (completed 1969), built primarily for flood risk reduction on the CHARITON RIVER; earth-type dam, 100 ft tall and 10,120 ft long.
- Surface area
- 11,013 ac
- Normal storage
- 205,359 ac-ft
- Max storage
- 552,000 ac-ft
- Drainage area
- 549 sq mi
- Hazard class
- High
- Owner
- USACE - Kansas City District
All listed purposes: Flood Risk Reduction;Other;Navigation;Fish and Wildlife Pond;Recreation.
Source: USACE National Inventory of Dams, NID ID IA00016 · Operator website
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
4 EPA-permitted facilities operate within about 5 miles of Rathbun Lake under Clean Water Act (NPDES) discharge permits. 4 facilities have a reported Clean Water Act violation in the past three years.
- Rathbun Regional Water AssociationCenterville · 0.6 mi away · NPDES IA0075418Recent violation
- Dnr Rathbun Fish HatcheryMoravia · 0.7 mi away · NPDES IA0054844Recent violation
- Parkside Knolls HoaMoravia · 3.9 mi away · NPDES IA0053188Recent violation
- Mystic City Of StpMystic · 4.3 mi away · NPDES IA0071064Recent 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)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-09-17
Monitoring stations: 1