Where is Lake Decatur?

Lake Decatur is a lake in Macon County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.

How deep is Lake Decatur?

Lake Decatur has a maximum depth of 28 feet and an average depth of 7 feet. The lake covers 2904 acres.

Are there boat ramps on Lake Decatur?

Lake Decatur has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Lake Decatur, Lake Decatur. Public access is listed as yes.

Can I fish at Lake Decatur?

Lake Decatur has 2 documented boat landings 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.

Lake Decatur

Macon County, Illinois2,904 acresView map Directions

No nutrient or algae sampling on record from Illinois EPA for this lake.

Max depth

28 ft

Bathymetric survey

Area

2,904 acres

Surface area

Shoreline

46.2 mi

Measured length

Impaired · Mercury
28 ft max depth
Public access

See the measurements Directions Where to stay

Lake Decatur in Macon County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 28 ft. Surface area: 2904 acres.

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Lake Decatur is a 2,904-acre lake in Macon County, Illinois with a maximum depth of 28 feet (7-foot average). Limited fish-species data available. Public access is available with 2 public boat landings.

Source: EPA Water Quality Portal sampling records, Illinois EPA. Methodology: how these readings are compared.

What Lake Decatur is good for

From access and monitoring records, not editorial picks.

Boat launch2 documented ramps
Big water2,904 acres

Swimming conditions

No reading

Not rated

Nutrient and algae readings are not a swimming clearance. Lake Decatur is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury), nutrients (phosphorus, nitrogen), pesticides, pCBs. Check local advisories before you swim.

Whether Lake Decatur 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.

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Water quality measurements for Lake Decatur

These are the measurements Illinois EPA publishes for Lake Decatur, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

No clarity data. TSI undefined.

Ask about Lake Decatur

Answers come straight from the public measurements and survey records on this page.

Lake Details

Max depth

28 ft

Average depth

7 ft

Surface area

2,904 acres

Shoreline

46.2 mi

Public access

Yes

Listed by Illinois EPA

Recreation & Access

Boat Landings

Yes

Public Access

Lake DecaturPublic
Lake DecaturPublic

Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps

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Stays near Lake Decatur

Compare lakeside cabins, hotels, and vacation rentals near Lake Decatur in Macon 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 Decatur

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Fishing Lake Decatur

→ Lake Decatur fishing regulations (limits, seasons, special rules)

EPA Impairment Status

Lake Decatur is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

MercuryMetals (other than mercury)Nutrients (phosphorus, nitrogen)PesticidesPCBs

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_REA · Official waterbody report

Nearby Lakes in Macon County

Decatur Lake1.3 ft clear · Eutrophic1.6 miView →Weldon Springs Lake18.4 miView →Lake Clinton21.8 miView →Lake Shelbyville26.7 miView →Wood Lake26.7 miView →Bertinetti Lake29.7 miView →

Frequently asked questions about Lake Decatur

Where is Lake Decatur?: Lake Decatur is a lake in Macon 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 Decatur?: Lake Decatur in Macon County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 28 ft. Surface area: 2904 acres.
Is Lake Decatur safe to swim in?: Nutrient and algae readings are not a swimming clearance. Lake Decatur is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury), nutrients (phosphorus, nitrogen), pesticides, pCBs. Check local advisories before you swim.
How deep is Lake Decatur?: Lake Decatur has a maximum depth of 28 feet and an average depth of 7 feet. The lake covers 2904 acres.
Are there boat ramps on Lake Decatur?: Lake Decatur has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Lake Decatur, Lake Decatur. Public access is listed as yes.
Can I fish at Lake Decatur?: Lake Decatur has 2 documented boat landings 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.