Tecumseh Lake is a 13-acre productive, nutrient-rich eutrophic lake in Hardin County, Illinois. Water quality is graded B based on 2 sampling years through 2020.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2020-10-29. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Murky, only visible to about 3.6 ft. Phosphorus level: 18 µg/L. Trophic State Index: 52.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.6 ft | D |
| Phosphorus | 18 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 52 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 13 acres |
Where to stay near Tecumseh Lake
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Fishing Tecumseh Lake
Water Temperature
Tecumseh Lake averages about 80°F at the surface in summer, usually warmest in Jul (about 82°F) and coldest in Apr (about 60°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 164 field readings (2010–2020) via the EPA Water Quality Portal. See the full Tecumseh Lake water temperature breakdown →
Location
County Ranking
Ranked #1 of 1 lakes in Hardin County
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Reservoir Info (USACE NID)
Tecumseh Lake is a man-made reservoir impounded by the Techumseh (completed 1976), built primarily for recreation on the TR-BIG CREEK; other-type dam, 26 ft tall and 550 ft long.
- Surface area
- 13 ac
- Normal storage
- 75 ac-ft
- Max storage
- 100 ac-ft
- Drainage area
- 0 sq mi
- Hazard class
- Low
- Owner
- USDA FS
Source: USACE National Inventory of Dams, NID ID IL50614 · Operator website · Matched by proximity (0.14 km)
Regulated Pollution Sources Nearby
7 EPA-permitted facilities operate within about 5 miles of Tecumseh Lake under Clean Water Act (NPDES) discharge permits. 4 facilities have a reported Clean Water Act violation in the past three years.
- Elizabethtown Stp, Village OfElizabethtown · 2.5 mi away · NPDES IL0074250Recent violation
- Responsible Energy Operations LlcElizabethtown · 3 mi away · NPDES IL0080095Recent violation
- Hastie MineRosiclare · 3.5 mi away · NPDES IL0073385Recent violation
- Illinois American Water - Rosiclare StpRosiclare · 4.8 mi away · NPDES IL0034207Recent violation
- Elizabethtown, Village OfElizabethtown · 2.8 mi away · NPDES IL0028690
- Ozark-Mahoning CompanyRosiclare · 4.2 mi away · NPDES IL0032379
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2020-10-29
Monitoring stations: 2