pH
The pH measurement indicates how acidic or basic a solution is and ranges from 0 (very acidic) to 14 (very basic), with 7 being neutral. Kentucky's water quality criteria require pH to be within the range of 6.0 and 9.0 SU to protect aquatic life. When the water's pH is above this range (more basic) or below this range (more acidic), organisms may move away, stop reproducing, or die. Water with a low pH also allows toxic compounds to become more available in the water, possibly harming aquatic life.
Dissolved Oxygen
Oxygen is one of the most important constituents in aquatic systems because it supports the necessary metabolic processes of aerobic organisms (e.g., fish, insect larvae) and controls many inorganic and organic chemical reactions.
Natural occurrence
Oxygen is constantly being exchanged between surface waters and the atmosphere, through diffusion, aeration, (vertical mixing of water, as in riffles), and via oxygen-containing inorganic and organic compounds. The maximum possible concentration of dissolved oxygen (DO) in water is controlled by atmospheric pressure and water temperature.
How much matters?
DO values less than 5 mg/L are problematic over time for aquatic organisms, resulting in increased susceptibility to environmental stresses, reduced growth rates, mortality, and an alteration in the distribution of aquatic life.
Human impacts on concentrations
Water temperature increases when shade trees are removed from streambanks, warmed urban runoff waters enter a stream, or power plants release water used to cool their equipment. The warmed waters naturally hold less oxygen.
Temperature
Temperature affects the metabolic processes of aquatic organisms, as well as the solubility and toxicity of chemical compounds. Generally, the solubility of solids increases with increasing temperature, while gases tend to be more soluble in cold water.
Natural occurrence
Temperature varies naturally on a daily and seasonal basis. Natural factors affecting water temperatures in streams include direct sunlight and warm water outflows from shallow ponds or reservoirs.
How much matters?
Activities that change water temperatures beyond natural ranges should be avoided, and are prohibited under Clean Water Act rules. Appropriate temperatures are dependent on the type of stream and where it is located.
Human impacts
Removal of shading riparian (streamside) vegetation and releases of excessively warm water from industrial treatment facilities, wastewater and power plants, parking lots, roofs, and other areas can affect surface water temperatures.
Conductivity
Conductivity is a measure of the capacity of the water to carry an electrical current. It can naturally vary depending on the location of the waterbody and the underlying bedrock and soils.
A conductivity measurement can also serve as a general indicator of water contamination. Inorganic substances conduct electrical current. So, as salinity increases, conductivity also increases. In contrast, organic compounds (e.g., oil) do not conduct electrical current as much and therefore have low conductivity in water.
Higher conductivity levels (from 500 to 1,000, depending on geographical location) cause stress on aquatic organisms and can impact water supplies for drinking water and industrial use.
E. coli
Escherichia coli (E. coli) is naturally found in the intestinal tract of all warm-blooded animals and does not represent a direct human health threat when found in natural streams and waterways. However, it is measured as an indicator of potential accompanying threats from fecal contamination, including waste from humans, livestock, wildlife, and pets.
Interpretation of results
- Excellent: 0-130 MPN/100ml
- Good: 130-240 MPN/100ml
- Fair: > 240 to 2,399 MPN/100 ml
- Poor: > 2,400 MPN/100 ml