Turbidity
Physical · measured in NTU
A measure of water cloudiness caused by suspended particles. It is not a contaminant on its own but a strong indicator of treatment effectiveness and pathogen risk.
Common sources
Soil erosion and runoff, sediment disturbance, algal blooms, and pipe corrosion or main breaks.
Health risks
High turbidity can shield microorganisms from disinfection and correlates with increased risk of waterborne gastrointestinal illness, even when other water quality parameters look acceptable.
Sources & further reading
- EPA — Turbidity
- Schwartz J, Levin R, Hodge K (1997), 'Drinking water turbidity and pediatric hospital use for GI illness in Philadelphia', Epidemiology, 8(6):615-620
How ClearDive rates severity
Readings are bucketed for map color-coding using thresholds referenced from EPA regulatory limits where available. This is a simplified public-awareness scale, not a substitute for certified lab analysis.
How to test for it
A turbidity tube or handheld NTU meter gives a fast, reliable field reading.