Timber Lake
Carroll County, IllinoisView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Limited data
Timber Lake in Carroll County, Illinois is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 11.5 ft visibility.
- Clarity
- 11.5 ft
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Watch Timber Lake’s letter
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Why Timber Lake has no grade
Timber Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Timber Lake is Not Rated — not an F. Its 11.5-foot median from 2 readings collected 2021 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by Illinois EPA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Timber Lake is a lake in Carroll County, Illinois.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2021-07-26. Grade methodology: LakeQuality methodology.
What Timber Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11.5 ft of visibility
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Timber Lake
These readings exist but are not enough for an A–F grade — see why.
Good clarity, visible to about 11.5 ft. TSI 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
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.
Graded lakes near Timber Lake
Timber Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Carroll County
Frequently asked questions about Timber Lake
Where is Timber Lake?
- Timber Lake is a lake in Carroll County, Illinois. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Timber Lake?
- Timber Lake in Carroll County, Illinois is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 11.5 ft visibility.
Is Timber Lake safe to swim in?
- The letter is 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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)