Olney East Fork Lake
Richland County, IllinoisView mapDirections
Nutrients and algae run above the regional average.
↓ down from C at the last regrade
- Eutrophic
- Impaired · Mercury
- #1 of 3 in the county
- 47 ft max depth
- Public access
- Limited data
Olney East Fork Lake in Richland County, Illinois has a water quality grade of D (Nutrient-rich). Water clarity: 3.2 ft visibility. Phosphorus: 37 µg/L. Chlorophyll-a (algae): 29.6 µg/L.
- Clarity
- 3.2 ft
- Typical in September
- 77°F
- Max depth
- ~47 ft est.
- Type
- Eutrophic
- Phosphorus
- 37 µg/L
- Chlorophyll-a
- 29.6 µg/L
- Public access
- Yes
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Stays near Olney East Fork Lake
Compare lakeside cabins, hotels, and vacation rentals near Olney East Fork Lake in Richland 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Olney East Fork Lake are listed below.
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Olney East Fork Lake is a productive, nutrient-rich eutrophic lake in Richland County, Illinois with an estimated average depth of about 47 feet. Water quality is graded D based on 2 sampling years through 2022. Limited fish-species data available. Public access is available. Compared to the 2 other monitored lakes in Richland County, Olney East Fork Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-10-31. 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 D is nutrients and algae, not a swimming clearance. Olney East Fork Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 3.2 ft of visibility. Phosphorus 37 µg/L. Chlorophyll-a 29.6 µg/L. TSI 60. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.2 ft | Not graded |
| Phosphorus | 37 µg/L | Good |
| Chlorophyll-a (Algae) | 29.6 µg/L | Poor |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Water Temperature
Olney East Fork Lake typically sits around 77°F at the surface in September. Summer average is about 80°F. Usually warmest in Jul (about 84°F) and coldest in Oct (about 61°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 181 field readings (2012–2022) via the EPA Water Quality Portal. See the full Olney East Fork Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~47 ft est. |
| Average Depth | ~36 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Illinois has not published bathymetry for Olney East Fork Lake.
Lake Size & Watershed
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.
Fishing Olney East Fork Lake
EPA Impairment Status
Olney East Fork Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RCC · Official waterbody report
County Ranking
Ranked #1 of 3 lakes in Richland County
Nearby Lakes in Richland County
Frequently asked questions about Olney East Fork Lake
Where is Olney East Fork Lake?
- Olney East Fork Lake is a lake in Richland County, Illinois. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Olney East Fork Lake?
- Olney East Fork Lake in Richland County, Illinois has a water quality grade of D (Nutrient-rich). Water clarity: 3.2 ft visibility. Phosphorus: 37 µg/L. Chlorophyll-a (algae): 29.6 µg/L.
Is Olney East Fork Lake safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Olney East Fork Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Olney East Fork Lake?
- Olney East Fork Lake typically sits around 77°F at the surface in September, from 181 EPA Water Quality Portal field readings (2012–2022). That is a typical value for the month, not a live reading.
How deep is Olney East Fork Lake?
- No published bathymetric survey covers Olney East Fork Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 47 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Olney East Fork Lake across LakeQuality
More Illinois Lake Rankings
Other Grade D Lakes in Illinois
Eutrophic Lakes in Illinois
Where this data comes from
40 measurements from 3 monitoring stations, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX40 samples · 2022
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (3)
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)