Corydon Reservoir
Wayne County, Iowa67 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Corydon Reservoir. Here is what has been measured.
- Hypereutrophic
- Impaired · Pesticides
- 21 ft max depth
- Limited data
Corydon Reservoir in Wayne County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 1.9 ft visibility. Phosphorus: 612 µg/L. Chlorophyll-a (algae): 44 µg/L. Surface area: 66.9 acres.
Free interactive depth-contour map of Corydon Reservoir, reaching a maximum surveyed depth of 10 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Corydon Reservoir is a 67-acre highly nutrient-loaded hypereutrophic lake in Wayne County, Iowa with an estimated average depth of about 21 feet. Overall water quality is declining over recent sampling years. Compared to the 2 other monitored lakes in Wayne County, Corydon Reservoir ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-09. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Corydon Reservoir is listed impaired under Clean Water Act §303(d) (IR 4A) for pesticides. Check local advisories before you swim.
Whether Corydon Reservoir is safe to swim in today is a call for the Iowa Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Corydon Reservoir
These are the measurements Iowa DNR publishes for Corydon Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 1.9 ft of visibility. Phosphorus 612 µg/L. Chlorophyll-a 44 µg/L. TSI 77.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 612µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 44µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 77 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Corydon Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~21 ft est.
Surface area
67 acres
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Iowa has not published bathymetry for Corydon Reservoir.
Lake Size & Watershed
Watershed (drainage) area
3 sq mi
HydroLAKES / HydroSHEDS
Shoreline
1.4 mi
HydroLAKES / HydroSHEDS
Elevation
1,053 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
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Stays near Corydon Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Corydon Reservoir in Wayne 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Corydon Reservoir are listed below.
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Fishing Corydon Reservoir
Water quality readings over time
2 seasons of samples on record (2023–2024). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Phosphorus
Improving-205.5 µg/L/yr2 years
Chlorophyll-a
Worsening+14 µg/L/yr2 years
Reservoir Info (USACE NID)
Corydon Reservoir is a man-made reservoir impounded by the Corydon Reservoir Dam (completed 1974), built primarily for recreation on the TR-WEST JACKSON CREEK; earth-type dam, 26 ft tall and 750 ft long.
- Surface area
- 66.9 ac
- Normal storage
- 420 ac-ft
- Max storage
- 870 ac-ft
- Drainage area
- 2.7 sq mi
- Hazard class
- Significant
- Owner
- City of Corydon
Source: USACE National Inventory of Dams, NID ID IA01641 · Operator website
EPA Impairment Status
Corydon Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Drinking water.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 05-CHA-1331 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Corydon Reservoir under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Corydon City Of StpCorydon · 0.8 mi away · NPDES IA0049573Recent 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.
Nearby Lakes in Wayne County
Frequently asked questions about Corydon Reservoir
Where is Corydon Reservoir?
- Corydon Reservoir is a lake in Wayne County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Corydon Reservoir?
- Corydon Reservoir in Wayne County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 1.9 ft visibility. Phosphorus: 612 µg/L. Chlorophyll-a (algae): 44 µg/L. Surface area: 66.9 acres.
Is Corydon Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Corydon Reservoir is listed impaired under Clean Water Act §303(d) (IR 4A) for pesticides. Check local advisories before you swim.
How deep is Corydon Reservoir?
- No published bathymetric survey covers Corydon Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 21 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 66.9 acres.
Explore Corydon Reservoir across LakeQuality
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Hypereutrophic Lakes in Iowa
Where this data comes from
30 measurements from 1 monitoring station, 2023–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX30 samples · 2023–2024
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- In-Vitro Determination of Chlorophyll
- ISU modification of APHA 2130-B
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)