Clear Lake
Cerro Gordo County, IowaView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- Impaired · Pathogens (E. coli, fecal)
- #2 of 4 in the county
- Public access
Clear Lake in Cerro Gordo County, Iowa has a water quality grade of D (Nutrient-rich). Water clarity: 2.1 ft visibility. Phosphorus: 52 µg/L. Chlorophyll-a (algae): 26.4 µg/L.
- Clarity
- 2.1 ft
- Typical in September
- 70°F
- Type
- Eutrophic
- Phosphorus
- 52 µg/L
- Chlorophyll-a
- 26.4 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
Stays via Stay22
Stays near Clear Lake
Compare lakeside cabins, hotels, and vacation rentals near Clear Lake in Cerro Gordo 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 Clear Lake are listed below.
Top-rated places to stay near Clear Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
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Watch Clear Lake’s letter
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Free interactive depth-contour map of Clear Lake, reaching a maximum surveyed depth of 22 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Clear Lake is a productive, nutrient-rich eutrophic lake in Cerro Gordo County, Iowa. 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. Compared to the 3 other monitored lakes in Cerro Gordo County, Clear Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-22. Grade methodology: LakeQuality methodology.
What Clear Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Clear Lake Water Quality Report Card (2026)
A printable one-page report card for Clear Lake: grade, clarity, phosphorus, algae, multi-year trend, depth, and fish — with sources.
Swimming Safety
Grade onlyBacteria A · advisory
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, Clear Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 8 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 2.1 ft of visibility. Phosphorus 52 µg/L. Chlorophyll-a 26.4 µg/L. TSI 63. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.1 ft | Not graded |
| Phosphorus | 52 µg/L | Fair |
| Chlorophyll-a (Algae) | 26.4 µg/L | Poor |
| Trophic State Index (TSI) | 63 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Current Conditions
USGS snapshot Jul 6, 2026, 5:00 AM from gauge 05460000 (Clear Lake at Clear Lake, IA). Station page ↗ — a live reading replaces this snapshot when the gauge responds. Missing live data is not an all-clear.
Water Temperature
Clear Lake typically sits around 70°F at the surface in September. Summer average is about 75°F. Usually warmest in Jul (about 80°F) and coldest in May (about 59°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 Clear Lake water temperature breakdown →
Recreation & Access
- Nelson StreetPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Clear Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.036 m/yr | 5 |
| Phosphorus | ↑ Improving | -6.85 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -1.46 µg/L/yr | 5 |
EPA Impairment Status
Clear Lake 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 02-WIN-841 · Official waterbody report
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Clear Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 2 facilities have a reported Clean Water Act violation in the past three years.
- Clear Lake Sanitary DistrictClear Lake · 1.5 mi away · NPDES IA0058441MajorRecent violation
- Randy'S Neighborhood MarketClear Lake · 2 mi away · NPDES IA0081108Recent violation
- Magellan Pipeline Company, LpClear Lake · 3.3 mi away · NPDES IA0074411
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 #2 of 4 lakes in Cerro Gordo County
Nearby Lakes With Higher Grades
Clear Lake holds Grade D. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Cerro Gordo County
Frequently asked questions about Clear Lake
Where is Clear Lake?
- Clear Lake is a lake in Cerro Gordo County, Iowa. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Clear Lake?
- Clear Lake in Cerro Gordo County, Iowa has a water quality grade of D (Nutrient-rich). Water clarity: 2.1 ft visibility. Phosphorus: 52 µg/L. Chlorophyll-a (algae): 26.4 µg/L.
Is Clear Lake safe to swim in?
- Based on E. coli testing, Clear Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 8 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. Clear Lake 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 Clear Lake?
- Clear Lake typically sits around 70°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.
What is the water level at Clear Lake?
- The USGS snapshot on this page for Clear Lake is 5.1 ft of gage height, recorded Jul 6, 2026, 5:00 AM at gauge 05460000. 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 Clear Lake?
- Clear Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Nelson Street. Public access is listed as yes.
Explore Clear Lake across LakeQuality
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Where this data comes from
75 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_WQX75 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)
Named boat-access points from the USGS National Boat Ramps inventory