Tecumseh Lake
Hardin County, Illinois13 acresView mapDirections
Illinois EPA publishes the water-quality measurements for Tecumseh Lake. Here is what has been measured.
- Eutrophic
- Limited data
Tecumseh Lake in Hardin County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 3.6 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 22.5 µg/L. Surface area: 13 acres.
Tecumseh Lake is a 13-acre productive, nutrient-rich eutrophic lake in Hardin County, Illinois.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2020-10-29. Methodology: how these readings are compared.
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. Check local advisories before you swim.
Whether Tecumseh 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 Tecumseh Lake
These are the measurements Illinois EPA publishes for Tecumseh Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 3.6 ft. Phosphorus 27 µg/L. Chlorophyll-a 22.5 µg/L. TSI 57.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 27µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 22.5µg/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. | 57 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Tecumseh Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Tecumseh Lake typically sits around 63°F at the surface in October. Summer average is about 80°F. Usually warmest in Jul (about 82°F) and coldest in Apr (about 60°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (60°F) to its warmest (82°F).
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 →
Lake Details
Surface area
13 acres
No bathymetric survey has been published for Tecumseh Lake, so its depth is not documented here.
Stays via Stay22
Stays near Tecumseh Lake
Compare lakeside cabins, hotels, and vacation rentals near Tecumseh Lake in Hardin 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 Tecumseh Lake are listed below.
Top-rated places to stay near Tecumseh Lake
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Fishing Tecumseh Lake
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.
Nearby Lakes in Hardin County
Frequently asked questions about Tecumseh Lake
Where is Tecumseh Lake?
- Tecumseh Lake is a lake in Hardin County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Tecumseh Lake?
- Tecumseh Lake in Hardin County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 3.6 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 22.5 µg/L. Surface area: 13 acres.
Is Tecumseh Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Tecumseh Lake?
- Tecumseh Lake typically sits around 63°F at the surface in October, from 164 EPA Water Quality Portal field readings (2010–2020). That is a typical value for the month, not a live reading.
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Where this data comes from
36 measurements from 2 monitoring stations, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX36 samples · 2020
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (2)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)