Testing the Health of a Waterway

PHYSICAL ASSESSMENTS

Several tests can be done to determine the health of a waterway. Physical assessments involve examining properties such as the sediment and substrate in the river, the temperature of the water, and the channel structure. Erosion can lead to an excess amount of soil entering the waterway. This can alter the turbidity of the water. The turbidity is a measure of the amount of light able to penetrate the water surface. Turbidity is an important physical property because the amount of light reaching the riverbed will directly affect the temperature of the water. A river must maintain its temperature levels to accommodate aquatic organisms in reproduction and oxygen demand and ward against the growth of disease-causing agents. The banks of the river play an important role in containing the water during flooding and providing a path for the river to run. Heavy erosion, unstable banks and man-made structures create poor conditions for the wildlife on the edge of the river as well as the aquatic life within the river. These parameters must be evaluated periodically to assure that the river is physically capable of sustaining a diverse ecosystem (Miller).

BIOLOGICAL TESTING

Biological testing involves macroinvertabrate surveys, testing for pathogens such as fecal coliform and identifying invasive species in or around the river. Invasive species are an indication that the water quality itself may not be bad, but the health of the ecosystem as a whole could be suffering. Natural, native species lack the ability to compete with some non-native species. An ecosystem dominated by non-native species will not function properly (Miller). Pathogen tolerance for waterways is determined at the state level. The TMDL standards developed for the Tye will define the amount of pathogens acceptable for this river. The Macroinvertabrate assessments identify indicator species. These aquatic species have very particular habitat requirements. The presence of macroinvertabrates that are sensitive to adverse conditions in the water indicate that the water is in good health. Another factor in water quality is the chemical health of the river.

CHEMICAL TESTING

Chemical parameters tested are pH, Dissolved Oxygen, Biological Oxygen Demand, nutrients such as phosphorus and nitrogen, toxics, and total dissolved or suspended solids (Miller). The Tye River, during monitoring by the DEQ, was tested sporadically for all of these properties. However, at every site dissolved oxygen and pH were tested. In some areas the pH was found to be 6.0 which is acidic (Tye River Data, DEQ 2000.2009). The trees and soil near the water could be the cause for the lower pH level, in that conifers produce high levels of organic acid during decomposition and some soils, like clay, are naturally acidic (Miller). The pH, on occasion, was tested as high as 9.0 (Tye River Data, DEQ 2000.2009). This could be due to the high algal concentration in the water. During the day, when algae is in photosynthesis it uses carbon dioxide which raises the pH. This pH level will drop during the night as the algae respire (Miller).

Dissolved oxygen (DO) describes the oxygen available in the water. Many factors contribute to the level of dissolved oxygen like water temperature, sediment in the stream and the respiration and photosynthesis taking place in the water. Dissolved oxygen is measured in milligrams per liter. A good level of DO is 5mg/L and above. It should not drop below 1-2 mg/L for more than a few hours. Low levels of DO is referred to as hypoxia (Resources, Dissolved Oxygen). Hypoxia is a condition that has been intensively studied in the Mississippi River where the river meets the Gulf of Mexico. A large amount of algal masses has been associated with hypoxia in the Mississippi River (Council). The Chesapeake Bay has also experienced low levels of DO. The lowest levels have been recorded during the summer and at the bottom waters. High levels of algae have been associated with the Bay’s low levels of DO. Algal masses can directly affect the DO content in the water by producing oxygen during the process of photosynthesis and then using all the produced oxygen during non-daylight hours. The algal cells use even more oxygen during decomposition. Therefore, large quantities of algae can have a negative effect on the entire body of water. DO levels, for this reason will be lower at the bottom of a river bed. Since 2000, DO in the Tye has not dropped below 7.0 mg/L. Available oxygen lower than that could be a potential threat to the trout population, which prefers DO levels to remain above 6.0 mg/L. The highest that the DO in the Tye River has reached is 16.7mg/L. These test results indicate that the Tye River has favorable conditions for aquatic life regarding oxygen availability (Tye River Data DEQ).