Clearest lakes in Japan
Clearest lakes in Japan: 159 named lakes have an official Secchi depth. The 20 below are ranked by that reading — water clarity, not a LakeQuality A–F grade.
Lake map
Highest Secchi readings in Japan
| Lake | Place | Total phosphorus | Chlorophyll-a | Secchi | Year |
|---|---|---|---|---|---|
| 支笏湖 | Hokkaido | 3.0 µg/L | — | 18 m | 2025 |
| 倶多楽湖 | Hokkaido | 3.0 µg/L | — | 17 m | 2024 |
| 本栖湖 | Yamanashi | 3.0 µg/L | — | 14 m | 2025 |
| 洞爺湖 | Hokkaido | 3.0 µg/L | — | 13 m | 2024 |
| 十和田湖 | Akita | 4.0 µg/L | — | 11 m | 2024 |
| 十和田湖 | Aomori | 4.0 µg/L | — | 10 m | 2024 |
| 猪苗代湖 | Fukushima | 5.0 µg/L | — | 10 m | 2024 |
| 田沢湖 | Akita | 3.0 µg/L | — | 10 m | 2024 |
| 味噌川ダム貯水池 | Nagano | 7.0 µg/L | — | 8.6 m | 2025 |
| 屈斜路湖 | Hokkaido | 6.0 µg/L | — | 8.3 m | 2024 |
| 池田湖 | Kagoshima | 4.0 µg/L | — | 8.0 m | 2025 |
| 中禅寺湖 | Tochigi | 5.0 µg/L | — | 7.8 m | 2024 |
| 芦ノ湖 | Kanagawa | 4.0 µg/L | — | 7.8 m | 2025 |
| 深山ダム貯水池 | Tochigi | 4.0 µg/L | — | 7.3 m | 2024 |
| 沼沢湖 | Fukushima | 4.0 µg/L | — | 6.8 m | 2024 |
| 小河内貯水池 | Tokyo | 8.0 µg/L | — | 6.5 m | 2025 |
| 早明浦ダム貯水池 | Kochi | 5.0 µg/L | — | 6.5 m | 2025 |
| 野尻湖 | Nagano | 5.0 µg/L | — | 6.3 m | 2025 |
| 川俣ダム貯水池 | Tochigi | 7.0 µg/L | — | 6.1 m | 2025 |
| 奥只見貯水池 | Niigata | 5.0 µg/L | — | 6.0 m | 2024 |
Showing 20 of 159 named lakes. Open a county or place page for the rest.
Frequently asked questions
- Which lakes in Japan are the clearest?
- 159 named lakes in Japan have an official Secchi depth. This page ranks the 20 deepest readings. Secchi is a clarity measurement, not a swim-safety class and not a LakeQuality A–F grade.
- Is clear water the same as clean water?
- No. Secchi measures how far a disk stays visible. A clear lake can still have bacteria, toxins, or contaminants this catalog does not grade. Open a lake page for the authority's values.
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