Hydrology-related problems associated with North Carolina's major estuaries and sounds include contamination of some estuaries with municipal and industrial wastes and drainage from adjacent intensively-farmed areas, and nuisance-level algal blooms. In addition, there is excessive shoaling in some navigation channels, saltwater intrusion into usually fresh estuarine reaches, too-high or too-low salinities in nursery areas for various estuarine species, and flood damage due to hurricanes.
The Cape Fear River is the only major North Carolina estuary having a direct connection to the sea. Short-term flow throughout most of its length is dominated by ocean tides. The estuarine reaches of the Neuse-Trent, Tar-Pamlico, Chowan, and Roanoke River systems are at least partly shielded from the effects of ocean tides by the Outer Banks and the broad expanses of Pamlico and Albemarle Sounds. With the probable exception of the Roanoke River, winds are usually the dominant short-term current-producing force in these estuaries and in most of Pamlico and Albemarle Sounds.
Freshwater entering the major estuaries is, where not contaminated, of acceptable quality for drinking with minimum treatment. However, iron concentrations in excess of 0.3 milligrams per liter sometimes occur and water draining from swampy areas along the Coastal Plain is often highly colored, but these problems may be remedied with proper treatment. Nuisance-level algal blooms have been a recurring problem on the lower estuarine reaches of the Neuse, Tar-Pamlico, and Chowan rivers where nutrients (compounds of phosphorous and nitrogen) are abundant. The most destructive blooms tend to occur in the summer months during periods of low freshwater discharge and relatively high water temperatures.
