Fairfield Lake
Wayne County, Illinois18 acresView mapDirections
Illinois EPA publishes the water-quality measurements for Fairfield Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
Fairfield Lake in Wayne County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 1.3 ft visibility. Phosphorus: 148 µg/L. Chlorophyll-a (algae): 35.4 µg/L. Surface area: 18 acres.
Fairfield Lake is a 18-acre highly nutrient-loaded hypereutrophic lake in Wayne County, Illinois. Overall water quality is improving over recent sampling years. Compared to the 2 other monitored lakes in Wayne County, Fairfield Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-10-24. 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. Fairfield Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Fairfield 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 Fairfield Lake
These are the measurements Illinois EPA publishes for Fairfield Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 1.3 ft of visibility. Phosphorus 148 µg/L. Chlorophyll-a 35.4 µg/L. TSI 72.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 148µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 35.4µg/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. | 72 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Fairfield Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Fairfield Lake typically sits around 63°F at the surface in October. Summer average is about 82°F. Usually warmest in Jul (about 86°F) and coldest in Nov (about 59°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (59°F) to its warmest (86°F).
Typical surface water temperature by month, from 91 field readings (2012–2022) via the EPA Water Quality Portal. See the full Fairfield Lake water temperature breakdown →
Lake Details
Surface area
18 acres
No bathymetric survey has been published for Fairfield Lake, so its depth is not documented here.
Stays via Stay22
Stays near Fairfield Lake
Compare lakeside cabins, hotels, and vacation rentals near Fairfield Lake in Wayne 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Fairfield Lake are listed below.
Top-rated places to stay near Fairfield Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
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Fishing Fairfield Lake
Water quality readings over time
2 seasons of samples on record (2021–2022). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Phosphorus
Improving-18 µg/L/yr2 years
Chlorophyll-a
Improving-7.9 µg/L/yr2 years
Reservoir Info (USACE NID)
Fairfield Lake is a man-made reservoir impounded by the Fairfield Side Channel Reservoir Dam (completed 1979), built primarily for water supply on the TRIB LITTLE WABASH R; earth-type dam, 16 ft tall and 1,850 ft long.
- Surface area
- 18 ac
- Normal storage
- 274.66 ac-ft
- Max storage
- 328.66 ac-ft
- Drainage area
- 0.03 sq mi
- Hazard class
- Low
- Owner
- CITY OF FAIRFIELD
Source: USACE National Inventory of Dams, NID ID IL50585 · Operator website · Matched by proximity (0.21 km)
EPA Impairment Status
Fairfield Lake 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: Aquatic life, Other.
Source: EPA ATTAINS assessment unit IL_RCZJ · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Fairfield Lake under Clean Water Act (NPDES) discharge permits.
- Fairfield Wtp, City OfFairfield · 0.3 mi away · NPDES IL0046248
- Fairfield Water Treatment Plant, City OfFairfield · 4.1 mi away · NPDES IL0079375
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 Wayne County
Frequently asked questions about Fairfield Lake
Where is Fairfield Lake?
- Fairfield Lake is a lake in Wayne County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Fairfield Lake?
- Fairfield Lake in Wayne County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 1.3 ft visibility. Phosphorus: 148 µg/L. Chlorophyll-a (algae): 35.4 µg/L. Surface area: 18 acres.
Is Fairfield Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Fairfield Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Fairfield Lake?
- Fairfield Lake typically sits around 63°F at the surface in October, from 91 EPA Water Quality Portal field readings (2012–2022). That is a typical value for the month, not a live reading.
Explore Fairfield Lake across LakeQuality
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Hypereutrophic Lakes in Illinois
Where this data comes from
38 measurements from 1 monitoring station, 2021–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX38 samples · 2021–2022
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)