赤城大沼
赤城大沼 in Gunma, Japan has official water-quality measurements, not a LakeQuality A–F grade. Water clarity: 3.8 m visibility. Phosphorus: 17 µg/L.
- Clarity
- 3.8 m
Why 赤城大沼 has no A–F grade
赤城大沼 in Japan is published with the authority's own measurements, not a LakeQuality letter. official authority class; not a LakeQuality A–F letter Sampling here has recorded water clarity and phosphorus, but not algae (chlorophyll-a).
A letter on the LakeQuality scale would be an invention, not an official class. Everything below that has been measured is still reported on this page.
Monitoring: the Ministry of the Environment (Japan).
赤城大沼 is a lake in Gunma County, Japan.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2024-10-15. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for 赤城大沼
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 12.3 ft. Phosphorus level: 17 µg/L. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.75 m | Not graded |
| Phosphorus | 17 µg/L | Not graded |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near 赤城大沼
Compare lakeside cabins, hotels, and vacation rentals near 赤城大沼 in Gunma, Japan — 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.
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Fishing 赤城大沼
Frequently asked questions about 赤城大沼
What is the water quality of 赤城大沼?
- 赤城大沼 in Gunma, Japan has official water-quality measurements, not a LakeQuality A–F grade. Water clarity: 3.8 m visibility. Phosphorus: 17 µg/L.
Is 赤城大沼 safe to swim in?
- 赤城大沼 has official nutrient and clarity measurements, not a bacteria swim class and not a safety clearance. Algal blooms, currents, and depth are not covered. Always check local notices before swimming.
Explore 赤城大沼 across LakeGrade
More lakes in Japan
Where this data comes from
27 measurements from 1 monitoring station, 2016–2024. Retrieved from Japan MOE public water-body monitoring (not the EPA Water Quality Portal) on 2026-08-16.
Collected and reported by
- Ministry of the Environment (Japan)
moe-jp27 samples · 2016–2024
Analytical methods
- MOE public water body monitoring (kosui, lakes)
Monitoring station identifiers (1)
1020080
Authority classifications are stored separately from LakeQuality A–F letters and are never blended. See methodology and data sources.
Data Sources
Water quality data from the EPA Water Quality Portal
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2024-10-15
Monitoring stations: 1