Alton Slough
Alton Slough in St. Charles County, Missouri is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 386 acres.
- Area
- 386 acres
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Why Alton Slough 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 Alton Slough, 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 Missouri DNR and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Alton Slough is a 386-acre lake in St. Charles County, Missouri.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled recent years. Grade methodology: LakeQuality methodology.
Watch Alton Slough water quality
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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 Alton Slough
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 Alton Slough
Compare lakeside cabins, hotels, and vacation rentals near Alton Slough in St. Charles County, Missouri — 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 Alton Slough
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 386 acres |
No bathymetric survey has been published for Alton Slough, so its depth is not documented here.
Fishing Alton Slough
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Frequently asked questions about Alton Slough
Where is Alton Slough?
- Alton Slough is a lake in St. Charles County, Missouri. LakeQuality has not rated this lake (UNRATED) — no water-quality sampling on record for this lake.
What is the water quality grade for Alton Slough?
- Alton Slough in St. Charles County, Missouri is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 386 acres.
Is Alton Slough safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Alton Slough is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
Explore Alton Slough across LakeQuality
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Where this data comes from
Measurements for Alton Slough come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.