Lake Cornelia
Wright County, IowaView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- Impaired · Turbidity
- #1 of 1 in the county
- 53 ft max depth
- Public access
Lake Cornelia in Wright County, Iowa has a water quality grade of D (Nutrient-rich). Water clarity: 2.5 ft visibility. Phosphorus: 37 µg/L. Chlorophyll-a (algae): 20.1 µg/L.
- Clarity
- 2.5 ft
- Typical in September
- 71°F
- Max depth
- ~53 ft est.
- Type
- Eutrophic
- Phosphorus
- 37 µg/L
- Chlorophyll-a
- 20.1 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
Stays via Stay22
Stays near Lake Cornelia
Compare lakeside cabins, hotels, and vacation rentals near Lake Cornelia in Wright 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 grade measures nutrients and algae, not lodging — cabins and rentals around Lake Cornelia are listed below.
Top-rated places to stay near Lake Cornelia
Prices for Sep 11–13, 4 adults. Change dates on the map below.
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Watch Lake Cornelia’s letter
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Free interactive depth-contour map of Lake Cornelia, reaching a maximum surveyed depth of 20 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Lake Cornelia is a productive, nutrient-rich eutrophic lake in Wright County, Iowa with an estimated average depth of about 53 feet. Water quality is graded D based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-22. Grade methodology: LakeQuality methodology.
What Lake Cornelia is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
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, Lake Cornelia never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 11 samples across 3 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 (Nutrient-rich)
Very murky, less than 2.5 ft of visibility. Phosphorus 37 µg/L. Chlorophyll-a 20.1 µg/L. TSI 60. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | Not graded |
| Phosphorus | 37 µg/L | Good |
| Chlorophyll-a (Algae) | 20.1 µg/L | Poor |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Lake Cornelia typically sits around 71°F at the surface in September. Summer average is about 76°F. Usually warmest in Jul (about 81°F) and coldest in May (about 61°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 29 field readings (2010–2023) via the EPA Water Quality Portal. See the full Lake Cornelia water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~53 ft est. |
| Average Depth | ~11 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Iowa has not published bathymetry for Lake Cornelia.
Lake Size & Watershed
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.
Recreation & Access
- Lake Cornelia State Management AreaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Lake Cornelia
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.231 m/yr | 5 |
| Phosphorus | ↑ Improving | -5.65 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -1.78 µg/L/yr | 5 |
EPA Impairment Status
Lake Cornelia is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 04-UDM-1264 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Lake Cornelia under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Lake Cornelia Sanitary DistrictClarion · 0.3 mi away · NPDES IA0066401Recent 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 Wright County
Nearby Lakes in Wright County
Frequently asked questions about Lake Cornelia
Where is Lake Cornelia?
- Lake Cornelia is a lake in Wright County, Iowa. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Cornelia?
- Lake Cornelia in Wright County, Iowa has a water quality grade of D (Nutrient-rich). Water clarity: 2.5 ft visibility. Phosphorus: 37 µg/L. Chlorophyll-a (algae): 20.1 µg/L.
Is Lake Cornelia safe to swim in?
- Based on E. coli testing, Lake Cornelia never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 11 samples across 3 seasons. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Lake Cornelia has a water quality grade of D (Nutrient-rich). 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 Lake Cornelia?
- Lake Cornelia typically sits around 71°F at the surface in September, from 29 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Lake Cornelia?
- No published bathymetric survey covers Lake Cornelia, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 53 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Lake Cornelia?
- Lake Cornelia has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lake Cornelia State Management Area. Public access is listed as yes.
Explore Lake Cornelia across LakeQuality
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Where this data comes from
77 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX77 samples · 2020–2024
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory