Forbes Lake
Forbes Lake in Marion County, Illinois is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 523 acres.
- Area
- 523 acres
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Why Forbes Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Forbes Lake, no water-quality sampling on record for this lake.
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. 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.
Forbes Lake is a 523-acre lake in Marion County, Illinois.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled recent years. Grade methodology: LakeQuality methodology.
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Swimming Safety
Not ratedElevated nutrients
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Forbes Lake
These readings exist but are not enough for an A–F grade — see why.
No clarity data. Trophic State Index: undefined.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) |
Where to stay near Forbes Lake
Compare lakeside cabins, hotels, and vacation rentals near Forbes Lake in Marion 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 Forbes Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 523 acres |
No bathymetric survey has been published for Forbes Lake, so its depth is not documented here.
Recreation & Access
- Forbes LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Forbes Lake
Nearby Lakes in Marion County
Frequently asked questions about Forbes Lake
Where is Forbes Lake?
- Forbes Lake is a lake in Marion County, Illinois. LakeQuality has not rated this lake (UNRATED) — no water-quality sampling on record for this lake.
What is the water quality grade for Forbes Lake?
- Forbes Lake in Marion County, Illinois is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 523 acres.
Is Forbes Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Forbes Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
Are there boat ramps on Forbes Lake?
- Forbes Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Forbes Lake.
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Where this data comes from
Measurements for Forbes Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.
Other records on this page
Named boat-access points from the USGS National Boat Ramps inventory