1. Water Quality Indicators
A selection

2. pH Relative concentration of (in water)
Hydrogen ions H+
Hydroxide ions OH-
pH Scale is logarithmic (as you go up on the scale, it increases by a factor of 10)
Acid – pH less than 7
Alkaline – pH more than 7
Neutral is 7

3. pH and Water Quality
Very high or low pH values are toxic to life in the stream
6.5 to 8.2 is optimal for most organisms
Factors that affect pH
Acid Rain (magnitude and frequency)
Area geology – Dissolved Minerals (limestone)
Algal Blooms
Industrial or Commercial Sources
Carbonic Acids from Respiration and Decomposition

4. Base Line pH

5. Dissolved Oxygen Oxygen gas dissolved in the water
Vital for the existence of aquatic organism
Key component in cellular respiration for both aquatic and terrestrial life.
Factors to affect DO levels
Aquatic plant populations (diversity and volume)
Decaying organic matter
Current velocity
Atmospheric Pressure
Human Activity

6. DO and Water Quality The larger the organism, the more DO it requires.
Trout need 6.5 mg/L
Mosquito Larvae need 1.0 mg/L
Sources of DO
Atmospheric Diffusion (air touching the water)
Aeration of water (white water)
Photosynthesis of primary producers (plants)
Higher in the day or night??

7. Fish Kills

8. Nitrates and Phosphates
Necessary nutrients for aquatic plants and algae (only small amounts needed)
Excessive amounts = eutrophication
Two types – Organic and Inorganic
Organic (human or animal waste)
Inorganic (fertilizers and detergents)

9. Nutrients and Water Quality
High levels
Eutrophication of aquatic ecosystem
Increased algal blooms
Decreased DO
Nitrates and Phosphates easily dissolve in water (percolation and runoff enable this)
Common sources – Factories, urban runoff, farms, decomposition of plants and animals

10. Nitrogen Cycle

11. Algal Bloom

12. Water Temperature How warm or cool the water is
Abnormal temperatures are toxic to aquatic life (too warm or cold)
Small changes can have a huge impact (even 1 degree)
Temperature affects DO levels (warm=less and cool=more)

13. Temperature and Water Quality
Warm Temps – Thermal Pollution – will kill fish and increase photosynthesis (algal blooms)
Example: Trout 5-20 degrees C, Caddisfly Larvae 10 to 25 degrees C
Factors to Affect Temperature
Air temp
Amount of Shade
Soil erosion (too much sediment)
Human Activity (power plants)
Where streams meet

14. Human Activity

15. Others Parameters Not Discussed
BOD – Biological Oxygen Demand
TDS – Total Dissolved Solids
Specific Conductivity
Turbidity

16. Homework Project
Each group should pick one factor and research it thoroughly
Discuss examples of how that factor affected a stream, lake or pond.
Next Tuesday, May 10, you will present your findings to the class (powerpoint or posterboard)