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. Water clarity is declining over recent sampling years. Limited fish-species data available. Public access is available with 5 public boat landings. 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: LakeGrade methodology.
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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
Based on E. coli testing, Clear Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 16.1% of 112 samples across 7 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 2.1 ft of visibility. Chlorophyll-a: 26.4 µg/L. Trophic State Index: 65.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.1 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 26.4 µg/L | D |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay 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.
Top-rated places to stay near Clear Lake
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Fishing Clear Lake
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.036 m/yr | 5 |
| Chlorophyll-a | ↑ Improving | -1.46 µg/L/yr | 5 |
Recreation & Access
Current Conditions
Latest reading Jul 6, 2026, 5:00 AM from USGS gauge 05460000. See live data ↗ — readings update every 15–60 minutes; this page refreshes on each build.
Water Temperature
Clear Lake averages about 75°F at the surface in summer, 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 →
Location & Depth Map
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.
County Ranking
Ranked #2 of 4 lakes in Cerro Gordo County
Cleaner Lakes Within 30 Miles
Clear Lake holds Grade D. 2 nearby lakes hold higher grades.
- ABlue Pit LakeCerro Gordo County · 10 mi · Two grade letters higher (D → A)
- BRudd LakeFloyd County · 26.5 mi · Two grade letters higher (D → B)
Nearby Lakes in Cerro Gordo County
Explore Clear Lake across LakeGrade
More Iowa Lake Rankings
Other Grade D Lakes in Iowa
Eutrophic Lakes in Iowa
More records, surveys & data sources
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
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
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: 2024-10-22
Monitoring stations: 1