Observed arrival · 2026-11-11
Machino Suishitsu Kurabe: Japan’s waterways, measured over time
This public-data explorer presents annual water-quality readings for Japanese rivers, lakes, and coastal waters, with comparisons by prefecture and trends at individual measurement sites.
- For
- Residents comparing nearby waterways over time
- Worth noticing
- It explicitly warns that station readings are not rankings of prefectural water quality or verdicts on swimming, drinking, or fish safety.
Field notes
The page separates rivers, lakes, and coastal waters, and keeps BOD and COD comparisons distinct rather than combining them into a single ranking. Its notes explain that station placement varies by prefecture, that “<0.5” means all samples were below the reporting limit, and that the figures describe annual results—not current conditions. The source list names annual-value, sample-value, and measurement-point datasets.
Observed signals
Read the marks
Editorial observations of this landing page, not a rating.
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