Black Pit Lake
Cerro Gordo County, IowaView mapDirections
Iowa DNR publishes the water-quality measurements for Black Pit Lake. Here is what has been measured.
- Hypereutrophic
Black Pit Lake in Cerro Gordo County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 5.6 ft visibility. Phosphorus: 55.3 µg/L. Chlorophyll-a (algae): 39.7 µg/L.
Black Pit Lake is a highly nutrient-loaded hypereutrophic lake in Cerro Gordo County, Iowa. Overall water quality is improving over recent sampling years. Compared to the 3 other monitored lakes in Cerro Gordo County, Black Pit Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2022-09-12. Methodology: how these readings are compared.
Swimming conditions
Readings onlyAlgae risk
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. Check local advisories before you swim.
Whether Black Pit Lake 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 Black Pit Lake
These are the measurements Iowa DNR publishes for Black Pit Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 5.6 ft. Phosphorus 55.3 µg/L. Chlorophyll-a 39.7 µg/L. TSI 60.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 55.3µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 39.7µg/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. | 60 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Black Pit Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Black Pit Lake typically sits around 76°F at the surface in August. Summer average is about 73°F. Usually warmest in Jul (about 76°F) and coldest in Jun (about 66°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (66°F) to its warmest (76°F).
Typical surface water temperature by month, from 9 field readings (2018–2022) via the EPA Water Quality Portal. See the full Black Pit Lake water temperature breakdown →
Stays via Stay22
Stays near Black Pit Lake
Compare lakeside cabins, hotels, and vacation rentals near Black Pit 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Black Pit Lake are listed below.
Top-rated places to stay near Black Pit Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
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Fishing Black Pit Lake
Water quality readings over time
3 seasons of samples on record (2020–2022). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Improving3 years
Phosphorus
Improving-20.1 µg/L/yr3 years
Chlorophyll-a
Improving-15.75 µg/L/yr3 years
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Black Pit Lake under Clean Water Act (NPDES) discharge permits.
- Golden Grain Energy, LlcMason City · 2 mi away · NPDES IA0078735
- Holcim (Us) Inc.Mason City · 4.8 mi away · NPDES IA0000388
- Amrize Cement Inc. - West QuarryMason City · 4.8 mi away · NPDES IA0071951
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 Cerro Gordo County
Frequently asked questions about Black Pit Lake
Where is Black Pit Lake?
- Black Pit Lake is a lake in Cerro Gordo County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Black Pit Lake?
- Black Pit Lake in Cerro Gordo County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 5.6 ft visibility. Phosphorus: 55.3 µg/L. Chlorophyll-a (algae): 39.7 µg/L.
Is Black Pit Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Black Pit Lake?
- Black Pit Lake typically sits around 76°F at the surface in August, from 9 EPA Water Quality Portal field readings (2018–2022). That is a typical value for the month, not a live reading.
Explore Black Pit Lake across LakeQuality
More lakes in Iowa
Other Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
36 measurements from 1 monitoring station, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX36 samples · 2020–2022
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)