Mattoon Lake
Cumberland County, Illinois980 acresView mapDirections
Illinois EPA publishes the water-quality measurements for Mattoon Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Algal growth
- 34 ft max depth
- Public access
- Limited data
Mattoon Lake in Cumberland County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 1.3 ft visibility. Phosphorus: 294 µg/L. Chlorophyll-a (algae): 87.1 µg/L. Surface area: 980 acres.
Mattoon Lake is a 980-acre highly nutrient-loaded hypereutrophic lake in Cumberland County, Illinois with an estimated average depth of about 34 feet. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-10-27. Methodology: how these readings are compared.
Mattoon Lake covers about 980 acres in Cumberland County. It has one public boat landing. If you are planning to stay, you can search lake houses and cabins around Mattoon Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Mattoon Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
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. Mattoon Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, mercury, nutrients (phosphorus, nitrogen), pesticides, turbidity. Check local advisories before you swim.
Whether Mattoon 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 Mattoon Lake
These are the measurements Illinois EPA publishes for Mattoon 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 294 µg/L. Chlorophyll-a 87.1 µg/L. TSI 78.
| 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 | 294µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 87.1µg/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. | 78 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Mattoon Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Mattoon Lake typically sits around 61°F at the surface in October. Summer average is about 78°F. Usually warmest in Jul (about 82°F) and coldest in Apr (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 (82°F).
Typical surface water temperature by month, from 101 field readings (2012–2022) via the EPA Water Quality Portal. See the full Mattoon Lake water temperature breakdown →
Lake Details
Max depth
~34 ft est.
Surface area
980 acres
Public access
Yes
Listed by Illinois EPA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Illinois has not published bathymetry for Mattoon Lake.
Lake Size & Watershed
Watershed (drainage) area
62 sq mi
HydroLAKES / HydroSHEDS
Shoreline
13.2 mi
HydroLAKES / HydroSHEDS
Elevation
630 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.
Recreation & Access
- Lake MattoonPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Mattoon Lake
Compare lakeside cabins, hotels, and vacation rentals near Mattoon Lake in Cumberland 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 Mattoon Lake are listed below.
Top-rated places to stay near Mattoon Lake
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip? Cabins and lodging at Mattoon Lake → · more Illinois lake trips
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Fishing Mattoon Lake
Reservoir Info (USACE NID)
Mattoon Lake is a man-made reservoir impounded by the Lake Mattoon Dam (completed 1957), built primarily for recreation on the LITTLE WABASH RIVER; earth-type dam, 46 ft tall and 2,250 ft long.
- Surface area
- 980 ac
- Normal storage
- 11,820 ac-ft
- Max storage
- 22,569 ac-ft
- Drainage area
- 57 sq mi
- Hazard class
- Significant
- Owner
- CITY OF MATTOON
All listed purposes: Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IL00141 · Operator website
EPA Impairment Status
Mattoon 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: Drinking water, Fish consumption, Other.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RCF · Official waterbody report
Regulated Pollution Sources Nearby
4 EPA-permitted facilities operate within about 5 miles of Mattoon Lake under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Rich Overzet Private Sewage Disposal SystemNeoga · 1.1 mi away · NPDES IL0080269Recent violation
- Neoga Stp, City OfNeoga · 2.2 mi away · NPDES IL0030091Recent violation
- David L. Paul Private Sewage Disposal SystemNeoga · 0.3 mi away · NPDES IL0080305
- Josh Denson Private Sewage Disposal SystemNeoga · 0.6 mi away · NPDES IL0080208
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 Cumberland County
Frequently asked questions about Mattoon Lake
Where is Mattoon Lake?
- Mattoon Lake is a lake in Cumberland County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Mattoon Lake?
- Mattoon Lake in Cumberland County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 1.3 ft visibility. Phosphorus: 294 µg/L. Chlorophyll-a (algae): 87.1 µg/L. Surface area: 980 acres.
Is Mattoon Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Mattoon Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, mercury, nutrients (phosphorus, nitrogen), pesticides, turbidity. Check local advisories before you swim.
What is the water temperature of Mattoon Lake?
- Mattoon Lake typically sits around 61°F at the surface in October, from 101 EPA Water Quality Portal field readings (2012–2022). That is a typical value for the month, not a live reading.
How deep is Mattoon Lake?
- No published bathymetric survey covers Mattoon Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 34 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 980 acres.
Are there boat ramps on Mattoon Lake?
- Mattoon Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lake Mattoon. Public access is listed as yes.
Can I fish at Mattoon Lake?
- Mattoon Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Illinois's fish and wildlife agency, so check its current regulations before you go.
Explore Mattoon Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at Illinois's top lakes, each with its readings
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Where this data comes from
77 measurements from 5 monitoring stations, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX77 samples · 2022
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (5)
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)
Named boat-access points from the USGS National Boat Ramps inventory