pH
What is it?
The pH measurement shows how acidic or basic a water body is. The amount of hydrogen ion activity in water determines the level of pH on a scale from 0-14. The lower the pH value, the more acidic the water is. The pH range for natural bodies of The water in the United States is around 6.5-8.5.
Why do we measure it?
The pH is an important water quality parameter. Aquatic animals and plants are adapted to a certain pH range, but most prefer between 6.5-8.0. An increase or decrease in pH outside the normal range of a water body can be detrimental to organisms depending on their sensitivity.
Source: US EPA
What affects it?
A variety of natural and human factors can influence the pH level of a body of water. For example, water can be made more acidic by acid rain or the vegetation found near the water. The acidity of a lake or pond also depends upon its age. Older bodies of water typically have more organic material, which leads to lower pH levels as the organic material decays. Regardless of which end of the spectrum a pH level may gravitate toward, extremes in the pH level can be damaging to most aquatic organisms.
Source: Michigan Sea Grant