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.  Fecal matter can contain bacteria and pathogens that may cause waterborne diseases or infections.  Therefore, high E. coli concentrations indicate the greater likelihood that human contact with the water could cause health issues. 

To interpret your results, Watershed Watch uses the following assessment benchmarks:

• Excellent: 0-130 MPN/100ml

• Good: 130-240 MPN/100ml

• Fair: > 240 to 2,399 MPN/100 ml

• Poor: > 2,400 MPN/100 ml

Kentucky's Water Quality Standards apply to more frequent sampling than is conducted by Watershed Watch.

• <130 CFU/100 ml as a geometric mean based on no less than five samples taken during a 30 day period

OR

• <240 CFU/100 ml in 20% or more of all samples taken during a 30-day period

NOTE: CFU refers to “colony forming units”, whereas MPN refers to “most probable number”. The difference is that CFU/100ml is the actual count from the surface of a plate, and MPN/100ml is a statistical probability of the number of organisms (American Public Health 2012) 

Dissolved Oxygen

Oxygen is one of the most important constituents in aquatic systems, because it supports metabolic processes of aerobic organisms (e.g., fish, insect larva) 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. Oxygen saturation in water is proportional to atmospheric pressure and inversely proportional to water temperature, so the cooler the water the greater the DO concentration.

Biologic processes add and remove oxygen from a waterbody. In a nutrient-rich water body, the DO can be quite high in the surface water during the day due to photosynthesis from algae and aquatic plants, and low at night due microorganism respiration (biologically mediated oxidation). DO can also be chemically removed - or bound up - by oxidation of other constituents in the water, such as iron.

Because of daily temperature cycles and because photosynthesis and respiration is controlled by sunlight, the DO concentration in water tends to undergo diurnal cycles: DO is higher during periods of sunlight, and lower at night.

In aquatic systems, the physical, chemical and biologic processes interact in complex ways. For example, DO tends to be depleted in deeper waters because photosynthesis is reduced owing to poor light penetration and the fact that dead algae (phytoplankton) sinks, and is decomposed by aerobic bacteria and other microorganisms.

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. Levels that remain below 1-2 mg/L for a few hours can result in severe fish kill. A grab sample reading should be compared with the instantaneous minimum (acute) criteria, which is 4 mg/L. Mountain or spring-fed streams that are designated as cold-water aquatic habitat (i.e., for trout, etc.) require higher DO.

Human impacts on concentrations

Water temperature increases caused by removal of riparian shade trees, power plant releases, or urban stormwater decreases instream DO. Increased nutrient levels can cause excessive algal growth, resulting in decreased DO as algae dies and is decomposed by aerobic biota. 

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.

Temperature affects the metabolic processes of aquatic biota and the solubility and toxicity of other parameters. Generally, the solubility of solids increases with increasing temperature, while gases tend to be more soluble in cold water. For example, colder water has a greater capacity to retain dissolved oxygen than warmer water. Temperature is also a factor in determining allowable limits for other parameters, such as ammonia.

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. Groundwater - which averages between 55° and 60° F in Kentucky - can influence stream temperature. Mixing of shallow groundwater and surface water commonly occurs in the hyporheic zone, the subsurface area below and adjacent to stream channels where many organisms find refuge during drought and extreme temperatures.

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. Lowland streams are often categorized as "warmwater" systems, and are different from mountain or spring-fed "coldwater" streams that support organisms with lower temperature and higher oxygen requirements. Temperatures for warmwater streams should not exceed 89° F; coldwater streams should not exceed 68° Fahrenheit.

Higher temperatures can reduce oxygen concentrations and affect growth, reproduction, and metabolic processes in fish and other organisms - sometimes fatally. The table below lists regulatory requirements for seasonal temperature water quality standards.

Human impacts

Removal of shading riparian vegetation and discharges of excessively warm water from industrial treatment facilities, wastewater and power plants, parking lots, roofs, and other areas can affect surface water temperatures. Stormwater infiltration, cooling ponds, and riparian vegetation (e.g., shade trees, shrubs, native grasses) can help to mitigate these effects.