Rathbun Lake
Appanoose County, Iowa11,013 acresView mapDirections
Nutrients and algae sit mid-range for this region.
↑ up from D at the last regrade
- Eutrophic
- #1 of 1 in the county
- Public access
Rathbun Lake in Appanoose County, Iowa has a water quality grade of C (Fair). Water clarity: 3 ft visibility. Phosphorus: 48 µg/L. Chlorophyll-a (algae): 15.3 µg/L. Surface area: 11013 acres.
- Clarity
- 3 ft
- Typical in September
- 77°F
- Area
- 11,013 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
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Watch Rathbun Lake’s letter
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Rathbun Lake is a 11,013-acre productive, nutrient-rich eutrophic lake in Appanoose County, Iowa. Water quality is graded C based on 2 sampling years through 2024. Overall water quality is declining 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: LakeQuality methodology.
What Rathbun Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch6 documented ramps
- Big water11,013 acres
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
Grade onlyBacteria A
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.
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: C (Fair)
Very murky, less than 3 ft of visibility. Phosphorus 48 µg/L. Chlorophyll-a 15.3 µg/L. TSI 60. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3 ft | Not graded |
| Phosphorus | 48 µg/L | Fair |
| Chlorophyll-a (Algae) | 15.3 µg/L | Fair |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Current Conditions
USGS snapshot Sep 7, 2026, 3:45 PM from gauge 06903880 (Rathbun Lake near Rathbun, IA). Station page ↗ — a live reading replaces this snapshot when the gauge responds. Missing live data is not an all-clear.
→ Rathbun Lake water level: the live USGS gauge reading
Water Temperature
Rathbun Lake typically sits around 77°F at the surface in September. Summer average is about 76°F. 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 →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 11,013 acres |
| Public Access | Yes |
No bathymetric survey has been published for Rathbun Lake, so its depth is not documented here.
Recreation & Access
- Sharon Bluffs State ParkPublic
- Outlet ParkPublic
- Rathbun Wildlife Management AreaPublic
- Rathbun Wildlife Management AreaPublic
- Rathbun Wildlife Management AreaPublic
- Rathbun Wildlife Management AreaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Rathbun Lake
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.064 m/yr | 4 |
| Phosphorus | ↓ Declining | +5.75 µg/L/yr | 4 |
| Chlorophyll-a | ↓ Declining | +3.62 µg/L/yr | 4 |
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
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.
County Ranking
Ranked #1 of 1 lakes in Appanoose County
Nearby Lakes in Appanoose County
Frequently asked questions about Rathbun Lake
Where is Rathbun Lake?
- Rathbun Lake is a lake in Appanoose County, Iowa. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Rathbun Lake?
- Rathbun Lake in Appanoose County, Iowa has a water quality grade of C (Fair). Water clarity: 3 ft visibility. Phosphorus: 48 µg/L. Chlorophyll-a (algae): 15.3 µg/L. Surface area: 11013 acres.
Is Rathbun Lake safe to swim in?
- 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. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Rathbun Lake has a water quality grade of C (Fair). Bacteria levels can spike quickly after heavy rain, so always check Iowa's current beach and health-department advisories before you swim.
What is the water temperature of Rathbun Lake?
- Rathbun Lake typically sits around 77°F at the surface in September, from 26 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
What is the water level at Rathbun Lake?
- The USGS snapshot on this page for Rathbun Lake is 905.66 ft of gage height, recorded Sep 7, 2026, 3:45 PM at gauge 06903880. Current Conditions hydrates a live NWIS reading from that same station when the gauge responds. A missed live fetch is not an all-clear.
Are there boat ramps on Rathbun Lake?
- Rathbun Lake has 6 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Sharon Bluffs State Park, Outlet Park, Rathbun Wildlife Management Area, Rathbun Wildlife Management Area, among others. Public access is listed as yes.
Explore Rathbun Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at Iowa's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Iowa's cleanest and most-polluted lakes, ranked
More Iowa Lake Rankings
Other Grade C Lakes in Iowa
Eutrophic Lakes in Iowa
Where this data comes from
51 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_WQX51 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)
Named boat-access points from the USGS National Boat Ramps inventory