Classification of Waterbodies The State of North Carolina classifies surface waters (rivers, streams, lakes, swamps, ocean and coastal waterways) by human use and ecological/biological factors. Waterbodies may have multiple classifications to designate multiple uses or requirements for protection. Because water quality is affected by drainage from its watershed, surrounding land may also be given a classification.
More detailed classification information for specific portions of streams is listed in a table, one for each major river basin. All streams in Chapel Hill are in the Cape Fear River basin, and their classifications are listed alphabetically and hydrologically according to what subbasin they are in.
Water Quality Standards Water quality standards are based upon classification. Learn more about how classification, water quality standards, and protection or management strategies are applied to waterways.
Results from state water quality monitoring determine whether waterbodies meet standards or are impaired. If impaired, the sections of waterway are placed on a 303(d) list and will have requirements placed on the governing jurisdiction for improving the water quality.
Water Quality Impairment Poor water quality may result from direct discharges from pollutant sources, soil erosion, clearing of streamside vegetation, stormwater runoff, trash, and sewage. Pollution may come from a single, identifiable source (“point source”) or from a diffuse area as we find with stormwater runoff (“non-point source”).
When a waterbody is found to be impaired, NC DENR's Division of Water Resources (NCDWR) conducts studies to more precisely determine the cause of the problem. A management strategy or Total Maximum Daily Load (TMDL) for identified pollutants must be developed for all impaired waterbodies. EPA has an overview of impaired waters and the TMDL program.
The federal Clean Water Act Section 303(d), requires NCDWR to publish a biennial list of impaired waterbodies in need of a management strategy or TMDL for improvement. Section 305(b) of the Clean Water Act requires the state to publish a biennial Integrated Report that combines the 303(d) list with a comprehensive report of water quality conditions in the state. In NCDWR’s Integrated Reports, only waterbodies in Category 4 and Category 5 are rated as impaired. The report identifies which use of an impaired segment of stream or lake is affected, the reason for the rating, and when the waterbody was last rated. Some expected impaired stream segments may not appear on a given 303(d) list because a TMDL or management strategy has been developed for them, or for other reasons. To understand the history of a given stretch of stream it’s best to look at the Integrated Report, several years of data, or inquire with DWQ rather than to reference a single 303(d) list.