Surface Water Quality

​CMAN​N Links & Glossary

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Stream Use-Support Index

Flooding Information and Notification System

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Charlotte-Mecklenburg Storm Water Services

Glossary of Terms

​Definitions for some technical terms used on this website.

Conductivity

Conductivity measures ion concentration in water that can carry electricity dependent on temperature. The standard measurement is in siemens per meter, but freshwater monitoring measures in micro-siemens per centimeter. Local geology, natural occurrences, regulated discharges, and pollution can influence conductivity. In the streams and lakes, conductivity levels remain relatively constant and range between 150-300 µS/cm depending on the watershed.

Dissolved Oxygen

Dissolved oxygen (DO) measures oxygen gas molecules in water in milligrams per liter (mg/L). The amount of DO contributes to various biological processes in waterways and can be a limiting factor for aquatic life. On average, DO ranges from 6 mg/L to 12 mg/L and can fluctuate daily. Colder, winter water holds more dissolved oxygen than warmer, summer water. Photosyn​thesis also drives daily DO levels. During the day, aquatic plants produce oxygen from photosynthesis. At night, aquatic life consumes oxygen while no longer producing it, resulting in a diurnal oxygen cycle. Algal blooms alter this diurnal cycle by using more oxygen during the day than aquatic life produces, which can cause hypoxic conditions. Dissolved oxygen levels should not be below 4 mg/L which is considered hypoxic and is the North Carolina State Standard.

pH

pH is a measurement of hydrogen ions in an aqueous solution. Values range from 0 to 14 on a unit-less scale. Solutions with a pH value below 7 are acidic, and solutions with a pH value above 7 are basic (alkaline). Pure water is neutral with a pH of 7. In general, pH in the streams and lakes in Mecklenburg County read around 7 but can fluctuate daily and seasonally. The North Carolina State Standard for pH ranges between 6 and 9.

Temperature​

Water temperature changes daily and seasonally, which affects aquatic life and water chemistry. Due to water's high specific heat property, it retains heat longer than the air but also takes longer to heat up. Besides sunlight, industry and urban runoff can increase water temperatures beyond ambient levels. Aquatic organisms have an optimal temperature range for survival as well as other biological processes, such as reproduction. The North Carolina State Standard for temperature is 32°C (90°F) which means that the stream should not exceed this temperature anytime during the day.

Turbidity

Turbidity measures water clarity dependent on the amount of suspended particles. Turbidity is measured using an optical probe that shines light into the water and measures how well that light scatters in the water. Muddy and murky streams and lakes are a visual indicator of increased turbidity. Turbid streams and lakes can be attributed to upstream construction, pollution, rain events, and other natural occurrences. For streams, the North Carolina State Standard is 50 NTU. For lakes, the North Carolina State Standard is 20 NTU.