Indicators of Water Quality
The following water quality indicators are measured in New Hanover County creeks. These chemical, physical and bacterial indicators are monitored in order to measure the general water quality of each creek.
Nitrate + Nitrite
Nitrate + nitrite are plant nutrients that are important for phytoplankton and other aquatic vegetation, however, high levels of them can lead to algae blooms and eutrophication. Elevated levels may be the result of wastewater effluent, fertilizer runoff or stormwater runoff from land disturbing activities.
Orthophosphate
Orthophosphate is formed by natural processes but is a good indicator of man-made influences such as wastewater, runoff from agricultural sites and application of fertilizers. Increased levels contribute to eutrophication and threaten aquatic life.
Chlorophyll a
Chlorophyll a is a measure of phytoplankton biomass in the water. High levels can indicate the presence of an algae bloom. The N.C. Standard for chlorophyll a is 40 for both saltwater and freshwater.
Enterococcus
Enterococcus is one of several indicators of the presence of bacteria in water. High values of the bacteria are indicative of human, wildlife or domestic animal feces. Both enterococcus and fecal coliform are good measures of bacteria in water, but enterococcus provides a better measure in marine waters. The N.C. standard for human health in saltwaters varies depending on the swimming designation of that area. To read more about these standards, please scroll down to the bottom of this page.
Fecal Coliform
Fecal coliform is an indicator of bacteria in water. Elevated levels can be the result of the introduction of human and animal waste or stormwater runoff from land disturbing activities. The N.C. standard for human health is 200 organisms/100 mL in freshwaters and 14/100 mL in saltwaters.
Water Temperature
Water temperature is a measure of the thermal stratification of the water table. High water temperatures can lead to algae blooms which can be harmful to aquatic life.
Salinity
Salinity is a measure of salt in the water. High levels are found near saltwater sources, however, elevated levels in freshwater can indicate the presence of saltwater intrusion.
Conductivity
Conductivity is the measure of the water's ability to pass an electrical current. Levels are affected by the presence of dissolved solids, organic compounds and temperature. Most water bodies maintain a constant range of conductivity, so variations from that range can indicate the introduction of pollutants.
pH
The pH level in water is the measure of the water's reactive characteristics. High pH levels may indicate algae production while low pH levels may indicate the introduction of an acidic substance. The N.C. standard for freshwater is 6.0-9.0 and the N.C. standard for saltwater is 6.8-8.5.
Dissolved Oxygen
Dissolved oxygen is a measure of the amount of oxygen dissolved in water. It is one of the best measures of the health of the water. Adequate levels of dissolved oxygen are necessary for good water quality and for aquatic organisms to live. Low levels of dissolved oxygen threaten aquatic life and cause fish kills. Low dissolved oxygen can be an indicator of wastewater, eutrophication or stagnant waters. The N.C. standard for dissolved oxygen is 5.0 for freshwater and saltwater and 6.0 for high quality waters.
Turbidity
Turbidity is a measure of suspended matter in water. Suspended matter often includes mud, clay, silt and sand. High turbidity levels can indicate the presence of sediment from land disturbing activities or an abundance of phytoplankton. The N.C. standard for freshwater is 50 NTU and for saltwater is 25 NTU.
N.C. Department of Environmental and Natural Resources Coastal Recreational Water Designations
The NCDENR classifies coastal recreational waters for monitoring, evaluation and notification purposes. These classifications are separated in three tiers which are used to determine designated enterococcus standards and swimming advisory guidelines that apply to each swimming area.
Tier I swimming area - a swimming area used daily during the swimming season, including any public access swimming area and any other swimming area where people use the water for primary contact, including all oceanfront beaches. The enterococcus level in a Tier I swimming area shall not exceed a geometric mean of 35/100 mL in a minimum of five samples taken over the course of 30 days, or a single sample of 104/100 mL.
Tier II swimming area - a swimming area used an average of three days a week during the swimming season. The enterococcus level shall not exceed a single sample of 276/100 mL.
Tier III swimming area - a swimming area used an average of four days a month during the swimming season. The enterococcus level shall not exceed two consecutive samples of 500/100 mL.