Big Rock Lake
Kane County, IllinoisView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
- Eutrophic
- #1 of 1 in the county
- Limited data
Big Rock Lake in Kane County, Illinois has a water quality grade of B (Good). Water clarity: 8.1 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 10.4 µg/L.
- Clarity
- 8.1 ft
- Typical in August
- 58°F
- Type
- Eutrophic
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Big Rock Lake is a productive, nutrient-rich eutrophic lake in Kane County, Illinois. Water quality is graded B based on 1 sampling years through 2022.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-10-11. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLimited data
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.
The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: B (Good)
Moderate clarity, visible to about 8.1 ft. Phosphorus 10 µg/L. Chlorophyll-a 10.4 µg/L. TSI 46. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.1 ft | Not graded |
| Phosphorus | 10 µg/L | Not graded |
| Chlorophyll-a (Algae) | 10.4 µg/L | Good |
| Trophic State Index (TSI) | 46 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Big Rock Lake typically sits around 58°F at the surface in August. 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.
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 →
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.
County Ranking
Ranked #1 of 1 lakes in Kane County
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. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Big Rock Lake?
- Big Rock Lake in Kane County, Illinois has a water quality grade of B (Good). 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?
- The B is nutrients and algae, 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 58°F at the surface in August, from 231 EPA Water Quality Portal field readings (2022–2022). That is a typical value for the month, not a live reading.
Explore Big Rock Lake across LakeQuality
More Illinois Lake Rankings
Other Grade B Lakes in Illinois
Eutrophic Lakes in Illinois
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)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)