A more indepth look at pH (taken from our newsletter, Jan 2004)
back to the list of parameters

What is pH?
pH is a relative measure of alkalinity and acidity, it’s an expression of the number of free hydrogen atoms present. It’s measured on a scale of 1 to 14, with 7 indicating neutral – neither acid nor base; lower numbers show increasing acidity, whereas higher numbers indicate more alkaline waters. The pH scale is logarithmic and goes from 0 to 14. For each whole number increase (for example 1 to 2) the hydrogen ion concentration decreases tenfold and the water becomes less acidic. Therefore, small differences in numbers can be significant: a pH of 4 is a thousand times more acidic than a pH of 6.

Why is it important?
Most species of life have a specific pH range in which they can survive. A wide variety of aquatic animals prefer a range of 6.5-8.0 pH. If pH is altered beyond an organism’s normal range it will suffer and soon die off. Many pollutants push pH readings toward the extremes of the scale. A change of more than two points on the scale can kill many species of fish. At the extreme ends of the pH scale (2 or 13), physical damage to fish gills, fins, and exoskeleton occurs. Changes in pH can also alter the concentra-tions of other toxic substances in the water. For example, a decrease in pH below
6 may increase the amount of mercury soluble in water.

How do we measure pH?
There are several methods for measuring pH. The one we use at Stream Team is a pH meter. When placed in water, an electrical force produced between the internal solution and the water can be measured. This force is a measure of pH.

What factors affect pH?
Pure water has a pH of 7.0, so what gives our rivers and creeks different pH readings? pH can change due to external inputs, both manmade and natural.

For example:
•A change in tree type, for example: conifer needles are acidic and maple leaves are basic
•A change in stream bottom material, for example: gravel, silt, and bedrock all have different pH levels
•A large change in temperature can affect pH: in fresh water, increasing temperatures decreases pH
•A large change in algae growth can affect pH: when algae use CO₂, pH increases
•Acid rain or acid mine drainage can decrease pH

What are expected pH levels?
All liquids around us have an expected pH level. Examples of alkaline substances are blood (7.5), seawater (9.3), and household ammonia (11.4). Examples of acidic substances are urine (6.0), oranges (4.5), Coca Cola Classic (2.5) and the contents of your stomach (2.0). In fresh water, like our Stream Team sites, we want to see levels between 6.5 and 8.5. This range is healthy for most organisms that live in fresh water.

Stream Team pH results
Good news! In both Ventura and Goleta Stream Teams, we nearly always find pH levels within the healthy range (6.5 to 8.5). Out of 528 records, we have only exceeded this range 15 times. All of these exceedances were on the high end (over 8.5) and the highest number recorded was 9.0. The sites that most commonly exceeded the 8.5 limit were Ventura Site 2 (Stanley Drain) and Goleta Site AT3 (Atascadero at Puente); both of these sites exceeded the limit 4 times. See the results posted on page 4 of our Jan 2004 Newsletter