Dissolved oxygen is a measure of how much oxygen in the water is available to living aquatic organisms, making it a very important component of stream health. Although dissolved oxygen in a waterway typically fluctuates in any given year due to seasonal temperature differences, the concentration can produce adverse impacts if it falls below the TDEC daily average standard of 5mg/L with a minimum DO level of 4 mg/L for a single measurement. Low DO can be the result of high levels of biological and/or chemical oxygen-depleting substances or stagnant water during dry periods.

High and low pH values can be an indicator of multiple factors contributing to anthropogenic effects on a stream. These conditions can also be exacerbated by acidic rainfall. TDEC standards state that pH should be between 6.0 – 9.0 for wadeable streams and 6.5 – 9.0 for larger waterbodies.

Abrupt changes in concentrations and the fluctuation of conductivity within a watershed often indicates a discharge or source of pollution in the waterbody. A decrease in conductivity indicates dilution of the waterbody, which is usually the result of a storm event.

Temperature is important for many aspects of aquatic health. It plays a role in the growth, development and survival of fish and other animals that live in creeks and rivers. The warmer water is, the less oxygen it is able to contain and make available for those organisms. Temperature also affects the rates of nutrient cycling and other chemical reactions, including toxicity, within waterbodies.

Stage is the height of the surface of the water above a defined benchmark elevation. It is important for monitoring the volume of water flowing through a stream at any given time. Rating curves can be developed for monitoring sites and then used to convert stage into flow volume estimates. These data, along with rainfall data, are useful for calibrating models and predicting when flooding will occur.

E. coli

The significant presence of E. coli in a waterway is a strong indicator of human or animal waste contamination. Potential sources are sanitary sewer overflows, leaks in septic or sanitary sewer systems, human waste from homeless communities, and runoff from domestic or wild animal waste. TDEC’s single sample criteria for recreation is 487 CFU/100ml for exceptional waters and 941 CFU/100ml for other waters.

Total Nitrogen

Nitrogen is a key nutrient that stimulates the growth of aquatic plants and algae. Excess levels of nitrogen can lead to the overgrowth of these organisms, possibly resulting in oxygen depletion and unpleasing aesthetics.

• Nitrate + Nitrite
• Total Kjeldahl Nitrogen

Total Phosphorus

Similarly to nitrogen, phosphorus is another key nutrient that can lead to the excess growth of aquatic plants and algae groups.

Total Suspended Solids

Elevated TSS levels have a negative effect on macroinvertebrates/fish, stream aesthetics, water treatment costs (where applicable), and overall water quality. Excess TSS can also be an indicator of stream bank erosion or sediment runoff from construction.