Natural waters typically have a pH in which range?

• A. 5-7
• B. 7-9
• C. 6-8
• D. 6-9

Answer: (D)

Natural waters stay buffered around a neutral to slightly basic state most of the time, thanks to minerals like carbonates that neutralize acids and bases. Because of this buffering, the pH values you typically see in streams, rivers, and lakes fall roughly between about six and nine. The range that best captures this common variability is six to nine, since it includes waters that are just slightly acidic, neutral, and up toward the alkaline side.

Choosing ranges like five to seven would miss the waters that sit around neutral to slightly alkaline; seven to nine would miss cleaner, slightly acidic examples; and six to eight doesn’t account for scenarios where pH can push toward nine in certain basins or under certain conditions.