Water quality is impacted by many different sources and types of pollution, according to the Ohio EPA. Under the Clean Water Act, each state must adopt water quality standards to protect their rivers, lakes and other surface waters. Water quality standards help determine the health of a water body and are used to help regulate the discharge of pollutants into those waters.
The health of a stream can be determined by collecting biological, chemical, and physical data and comparing it to water quality goals in the Ohio Water Quality Standards and to previous studies.
Biological data includes sampling for fish, macroinvertebrates (e.g., crayfish, worms) and amphibians (e.g., salamanders), as well as evaluating habitat (where the organisms live). Chemical and physical data includes testing water samples for bacteria (E. coli), dissolved oxygen, biochemical oxygen demand (BOD), metals, organics, flow and temperature, among others. The full list can be found in the study reports for each waterway.
The Ohio Water Quality Standards described below are most commonly used to help determine the health of a stream:
In the 1970s and 1980s, Ohio streams or segments of streams were evaluated and many were assigned an Aquatic Life Use classification. This Ohio Water Quality Standards classification system includes the following general categories:
Each water body is assigned a classification based on its potential for meeting the criteria for that classification (e.g., supporting a particular biological community).
Biological, chemical and physical data is then collected to determine whether the water body actually met the criteria (was in "attainment," "partial attainment" or "non-attainment" of the Aquatic Life Use classification). Attainment status does not apply to PHWH waters.
A body of water is in "attainment" if its chemical, biological and physical (habitat) integrity is maintained (as evaluated against water quality standards). Attainment means that a body of water capable of supporting a particular biological community is in fact supporting that biological community (e.g., trout in a cold water stream).
A body of water is in "partial attainment" or "non-attainment" when chemical, biological or physical indicators only partial attain the required condition for that parameter or are below the required condition.
A body of water is considered impaired if it is in partial or non-attainment.
If the biological health of the water is continually better or worse than in previous studies, the Aquatic Life Use classification may be recommended to be changed to another category which is more appropriate and attainable.
During the recreation season (May 1 to October 31), Ohio streams or segments of streams are assigned a Recreational Use designation that can help determine whether the water is safe for recreation based on a count of microbial pathogens (e.g., bacteria).
This designation is determined by the amount of physical contact a person might have with the body of water. In general, the water is assigned either:
Fecal bacteria (e.g., E. coli) are used as an indicator for the possible presence of pathogens in surface water. Pathogens can cause gastrointestinal disorders, ear and skin infections and respiratory issues.
Bacterial water quality standards have been established to determine when the concentration of fecal bacteria in water is too high and causes an unacceptably high health risk to humans who recreate in the waters.
Based on E. coli counts, a specific 30-day geometric mean has been established for the four Recreational Use classifications: PCA, PCB, PCC and SC.
Chemical data is then collected to determine whether the 30-day geometric mean for E. coli has been exceeded at a sampling location and therefore did not attain its Recreational Use status.
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