A Tale of Two Estuaries
Comparing Water Quality Problems and Management Approaches in the Neuse Basin in North Carolina and the Ashley-Cooper River Basins in South Carolina.
If Albert Einstein is correct and “everything is relative” perhaps a comparison of two different river basins in two different states will provide some useful insights. . The Neuse River Basin in North Carolina and the rivers flowing into Charleston Harbor in South Carolina – notably the Ashley River and the Cooper River have been the subjects of much public scrutiny and much technical study. What have we learned, and what questions remain?
Background
The Neuse Basin encompasses 3293 miles of freshwater streams, and about one-sixth of North Carolina residents reside within this Basin. Over 80% of the freshwater streams in the basin that have been monitored are classified either as impaired or as fully supporting but threatened. Important fisheries on the Neuse include flounder, catfish, bass, blue crabs, and oysters. The hog population in the Neuse River Basin increased by 250% between 1990 and 1998, and a statewide moratorium on the creation of new hog farms is currently in effect.
Although the Neuse has experienced a long series of fish kills, perhaps the most notable were the large fish kills of menhaden, flounder, croaker, and rock fish in the lower river during the Summer of 1995 and later that were accompanied by outbreaks of the toxic dinoflagellate Pfiesteria piscicida. In response to these fish kills, the NC General Assembly passed a package of new environmental laws (House Bill 1339) designed to reduce nitrogen loading to the Neuse River estuary by thirty percent within 5 years.
The Neuse River estuary is impaired as a result of phytoplankton blooms and excessive chlorophyll-a concentrations. Nitrogen is the main nutrient that scientists have identified as causing impairment in this estuary. Current federal mandates to the states, under Section 303(d) of the Clean Water Act, are to developNeuse River estuary is impaired as a result of phytoplankton blooms and excessive chlorophyll-a concentrations. Nitrogen is the main nutrient that scientists have identified as causing impairment in this estuary. Current federal mandates to the states, under Section 303(d) of the Clean Water Act, are to develop
restoration strategies or specify total maximum daily loads (TMDLs) of pollutants for impaired water bodies. The final TMDL for nitrogen control in the Neuse estuary was submitted to the U.S. Environmental Protection Agency (EPA) for approval on June 21, 1999, and EPA has already approved this TMDL. The TMDL requires a 30% reduction in total nitrogen loading to the estuary, and it allocates the allowable nitrogen load among point sources, agriculture, forestry, urban resources, and atmospheric sources.
Three river systems form the Charleston Harbor Estuary (CHE), the Cooper, the Ashley, and the Wando. Long-term trends in water quality monitoring and recent scientific research suggest that wasteload assimilation, nonpoint source runoff impacts, contaminated sediments, and toxic pollutants are key problems to be addressed. In addition, several toxic “hot spots” showing high levels of heavy metals and organic compounds have been identified. The CHE is important for shrimp and crab landings, and spot, while Atlantic croaker, red drum, spotted sea trout, flounder, and catfish also inhabit the estuary. The CHE is surrounded by urban development, and two sewage treatment plants discharge into the basin.
Of the three river systems forming the CHE, the Cooper River has the greatest number and density of industrial and port facilities, including the former U.S. Navy port facilities and commercial facilities associated with the State Ports Authority. Ninety-five percent of the total pollutant loads to the Cooper River are believed to be from point sources, and therefore of human origin.
Of the three rivers forming the CHE, the Ashley River basin has the second largest number of industrial and commercial facilities. There are seven municipal dischargers to the basin with a combined flow of 53 million gallons per day (mgd). Residential developments are located along both sides of the upper reaches of the Ashley River. Also, saltwater intrusion on this river varies widely with the hydrologic conditions of the basin. During dry periods, saltwater extends through most of the Ashley River, while during wet conditions, saltwater intrusion can be quite limited in extent. Portions of the Ashley have high turbidity levels, low dissolved oxygen, and elevated nutrient levels. Suggested causes of these water quality problems include fertilizer production, municipal discharges, and urban nonpoint source runoff.
Continue to Page 3 |
