What’s measured This measure looks at impaired stream miles as a percentage of total stream miles in the 11 North Carolina counties in the Charlotte region. It also examines monitoring sites reporting impaired streams in the three South Carolina counties in the region. Because of different reporting methodologies, data from the two states cannot be combined. The federal Clean Water Act requires states to collect and report data on streams with impaired water quality by measuring pollutants that exceed standards for the stream’s intended use or designation. State reports to the EPA under this provision of the Clean Water Act are referred to as each state’s “303(d)” list of impaired streams. Data for this indicator are from each state’s respective 303(d) annual report for 2006. However, since states are not required to use the same methodologies or formats, “303(d)” data from the two states in the region cannot be combined to create a regional indicator. In its 2006 report, North Carolina published a Geographic Information Systems map of perennial streams, rivers and lakes that showed impaired streams, making calculation of the stream-miles percentage practical for the first time. The term “stream” encompasses all surface waters, including rivers and lakes. Why it’s measured The quality of water in streams affects aquatic ecosystems and their ability to provide what have come to be known as “ecosystem services” to humans. Aquatic plants and animals that live in streams form the bottom of an ecological chain, the disruption of which has ripple effects far up the chain, including land-based animals. Also, water-supply and potable water treatment costs are affected, as well as the viability of streams for such activities as fishing, wading or swimming. Indicator results In 2006, impaired stream miles as a percentage of total stream-miles was 5.6 percent for the region’s 11 North Carolina counties. Of the 16,546 miles of streams in the North Carolina counties, 922 miles were impaired. In the South Carolina counties, 73 of 144 monitored stream locations reported impaired water quality. Evaluation Impaired streams occur in both urban and rural parts of the region, but are more prevalent downstream of urban areas. It would be misleading to construe the South Carolina indicator as a percentage for comparison to the North Carolina figure, since the location of monitored sites reflects locations of known and suspected pollution sources rather than a blanket monitoring of evenly distributed sites. Since the North Carolina indicator results also reflect locations of actual monitored sites, caution must be used in interpreting the indicator expressed as a percent of total stream miles. However, as long as the methodology for selecting monitor locations remains relatively stable in each state, the indicators can effectively track progress in maintaining or improving water quality over time. Connections The quality of water in streams reflects how we use land. It is affected by permitted and regulated discharges from public and industrial wastewater treatment systems as well as by accidental spills and stormwater runoff. Stormwater runoff can carry pollutants from roads, parking lots, lawns, constructions sites and agricultural areas. Such pollutants include sediment, bacteria, petroleum products from vehicles and nitrogen and other commercial fertilizer residue.
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