Big Rock Lake
Kane County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Big Rock Lake. Here is what has been measured.
- Eutrophic
- Limited data
Big Rock Lake in Kane County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 8.1 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 10.4 µg/L.
Big Rock Lake is a productive, nutrient-rich eutrophic lake in Kane County, Illinois.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-10-11. 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. Check local advisories before you swim.
Whether Big Rock Lake is safe to swim in today is a call for the Illinois Environmental Protection Agency and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Big Rock Lake
These are the measurements Illinois EPA publishes for Big Rock Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 8.1 ft. Phosphorus 10 µg/L. Chlorophyll-a 10.4 µg/L. TSI 46.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 8.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 10µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 10.4µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 46 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Big Rock Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Big Rock Lake typically sits around 54°F at the surface in October. Summer average is about 57°F. Usually warmest in Aug (about 58°F) and coldest in May (about 51°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (51°F) to its warmest (58°F).
Typical surface water temperature by month, from 231 field readings (2022–2022) via the EPA Water Quality Portal. See the full Big Rock Lake water temperature breakdown →
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Stays near Big Rock Lake
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Fishing Big Rock Lake
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Big Rock Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Big Rock Stp, Village OfBig Rock · 2.2 mi away · NPDES IL0079464Recent 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 Kane County
Frequently asked questions about Big Rock Lake
Where is Big Rock Lake?
- Big Rock Lake is a lake in Kane County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Big Rock Lake?
- Big Rock Lake in Kane County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 8.1 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 10.4 µg/L.
Is Big Rock 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 Big Rock Lake?
- Big Rock Lake typically sits around 54°F at the surface in October, from 231 EPA Water Quality Portal field readings (2022–2022). That is a typical value for the month, not a live reading.
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Where this data comes from
25 measurements from 2 monitoring stations, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX25 samples · 2022
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (2)
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)