Timber Lake
Carroll County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Timber Lake. Here is what has been measured.
- Limited data
Timber Lake in Carroll County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 11.5 ft visibility.
Timber Lake is a lake in Carroll County, Illinois.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2021-07-26. Methodology: how these readings are compared.
What Timber Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11.5 ft of visibility
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Timber 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 Timber Lake
These are the measurements Illinois EPA publishes for Timber Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 11.5 ft. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 11.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Timber Lake
Answers come straight from the public measurements and survey records on this page.
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Stays near Timber Lake
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Fishing Timber Lake
Reservoir Info (USACE NID)
Timber Lake is a man-made reservoir impounded by the Timber Lake Dam (completed 1960), built primarily for recreation on the TRIB EAST JOHNSON CREEK; earth-type dam, 25 ft tall and 466 ft long.
- Normal storage
- 87 ac-ft
- Max storage
- 155 ac-ft
- Hazard class
- Significant
- Owner
- TIMBER LAKE CAMPGROUND
Source: USACE National Inventory of Dams, NID ID IL00841 · Operator website
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Timber Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Mount Carroll Stp, City OfMount Carroll · 3.8 mi away · NPDES IL0020176Recent violation
- Harvel WtpHarvel · 3.5 mi away · NPDES IL0005029
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 Carroll County
Frequently asked questions about Timber Lake
Where is Timber Lake?
- Timber Lake is a lake in Carroll County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Timber Lake?
- Timber Lake in Carroll County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 11.5 ft visibility.
Is Timber Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Explore Timber Lake across LakeQuality
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Where this data comes from
2 measurements from 1 monitoring station, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North American Lake Management Society
NALMS2 samples · 2021
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)