Lake Opeka
Cook County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Lake Opeka. Here is what has been measured.
- Mesotrophic
- Impaired · Cause unknown
- 49 ft max depth
- Limited data
Lake Opeka in Cook County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 4 ft visibility. Phosphorus: 22.5 µg/L. Chlorophyll-a (algae): 5.3 µg/L.
Lake Opeka is a mesotrophic lake in Cook County, Illinois with an estimated average depth of about 49 feet. Overall water quality is declining over recent sampling years. Compared to the 15 other monitored lakes in Cook County, Lake Opeka ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-09-22. Methodology: how these readings are compared.
If you are planning to stay, you can search lake houses and cabins around Lake Opeka on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
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. Lake Opeka is listed impaired under Clean Water Act §303(d) (IR 5) for cause unknown. Check local advisories before you swim.
Whether Lake Opeka 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 Lake Opeka
These are the measurements Illinois EPA publishes for Lake Opeka, 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 4 ft. Phosphorus 22.5 µg/L. Chlorophyll-a 5.3 µg/L. TSI 51.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 22.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 5.3µg/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. | 51 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Lake Opeka
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lake Opeka typically sits around 58°F at the surface in October. Summer average is about 77°F. Usually warmest in Jul (about 79°F) and coldest in Oct (about 58°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (58°F) to its warmest (79°F).
Typical surface water temperature by month, from 43 field readings (2020–2022) via the EPA Water Quality Portal. See the full Lake Opeka water temperature breakdown →
Lake Details
Max depth
~49 ft est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Illinois has not published bathymetry for Lake Opeka.
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Surface area
37 acres
HydroLAKES / HydroSHEDS
Shoreline
1 mi
HydroLAKES / HydroSHEDS
Elevation
640 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Stays via Stay22
Stays near Lake Opeka
Compare lakeside cabins, hotels, and vacation rentals near Lake Opeka in Cook County, Illinois — 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 Lake Opeka
Prices for Oct 23–25, 4 adults. Change dates on the map below.
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Fishing Lake Opeka
Water quality readings over time
2 seasons of samples on record (2020–2022). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
EPA Impairment Status
Lake Opeka is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Other.
Source: EPA ATTAINS assessment unit IL_RGF · Official waterbody report
Regulated Pollution Sources Nearby
12 EPA-permitted facilities operate within about 5 miles of Lake Opeka under Clean Water Act (NPDES) discharge permits, including 2 classified by the EPA as major dischargers. 7 facilities have a reported Clean Water Act violation in the past three years.
- Mwrdgc- James Kirie WrpDes Plaines · 2 mi away · NPDES IL0047741MajorRecent violation
- Bensenville - South Stp, Village OfBensenville · 4.8 mi away · NPDES IL0021849MajorRecent violation
- Blackhawk Estates Mobile Home Community StpChicago · 1.8 mi away · NPDES IL0049859Recent violation
- Des Plaines Mobile Home Park StpDes Plaines · 2.2 mi away · NPDES IL0054160Recent violation
- Aircraft Service International Inc. D/B/A Menzies AviationChicago · 2.3 mi away · NPDES IL0066567Recent violation
- Aircraft Service International IncChicago · 2.4 mi away · NPDES IL0080235Recent 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 Cook County
Frequently asked questions about Lake Opeka
Where is Lake Opeka?
- Lake Opeka is a lake in Cook County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Lake Opeka?
- Lake Opeka in Cook County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 4 ft visibility. Phosphorus: 22.5 µg/L. Chlorophyll-a (algae): 5.3 µg/L.
Is Lake Opeka safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake Opeka is listed impaired under Clean Water Act §303(d) (IR 5) for cause unknown. Check local advisories before you swim.
What is the water temperature of Lake Opeka?
- Lake Opeka typically sits around 58°F at the surface in October, from 43 EPA Water Quality Portal field readings (2020–2022). That is a typical value for the month, not a live reading.
How deep is Lake Opeka?
- No published bathymetric survey covers Lake Opeka, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 49 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Lake Opeka across LakeQuality
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Other Lakes in Illinois
Mesotrophic Lakes in Illinois
Where this data comes from
53 measurements from 4 monitoring stations, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX52 samples · 2020 - USGS Illinois Water Science Center
USGS-IL1 sample · 2022
Analytical methods
- Secchi disk method
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (4)
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)