pH

pH is a measure of the relative acidity of water and is measured on a scale from 0 (most acidic) to 14 (most basic).

Why is it important?

pH affects water chemistry and the biological state of aquatic organisms.  Changes in pH affect the chemical balance of the ecosystem by making non-toxic substances toxic, or by disrupting an organism's absorption of compounds that are essential for growth and survival. For most aquatic organisms, changes in pH are very stressful, especially during reproduction.

What influences pH?

pH is affected by the type of rocks and soil in the area, as well as human additions, such as fertilizers, chemical spills, urban runoff, and acid rain.

What is considered healthy?

Surface waterbodies with pH ranging from 6 to 9 provide suitable habitat for most types of aquatic life.

Where can I find out more?

Factsheet on pH in lakes (pdf)
Factsheet on pH in streams and rivers (pdf)
Water on the Web