Chapter 6

Water Quality Stressors and Sources 57
Chapter 6
Water Quality Stressors and Sources of Impairment in the
Chowan River Basin

6.1 Stressor and Source Identification

Human activities can negatively impact surface water quality, even when the activity is far
removed from the waterbody. The many types of pollution generated by human activities may
seem insignificant when viewed separately, but when taken as a whole can result in significant
stress to the aquatic ecosystem. Water quality stressors are identified when impacts have been
noted to biological (fish and benthic) communities or water quality standards have been violated.
Stressors apply to one or more use support categories and may be identified for Impaired, as well
as Supporting waters with noted impacts.

For specific discussion of stressors and sources of the Impaired or waters with Noted Impacts,
refer to the subbasin chapters. More information regarding aquatic life, recreation, fish
consumption and shellfish harvesting stressors and sources can be found in Chapter 3 of the
Supplemental Guide to North Carolina's Basinwide Planning: Support Document for Basinwide
Water Quality Plans http://www.ncwaterquality.org/basinwide/SupplementalGuide.htm.

6.1.1 Stressors

Identifying stressors is challenging because direct measurements of the stressor may be difficult
or prohibitively expensive. DWQ staff use field observations from sample sites, special studies
and data from ambient monitoring stations, as well as information from other agencies and the
public to identify stressors and their potential sources. It is important to identify stressors and
potential sources of stressors so that water quality programs can target limited resources to
address the stressor.

Stressors to recreational use include pathogenic indicators such as fecal coliform bacteria,
escheria coli (E. coli), and enterrococci. In the fish consumption category, mercury and dioxin
are the noted stressors. Other substances may also result in the issuance of a fish consumption
advisory or advice by the NC Division of Health and Human Services (NCDHHS).

Most stressors to the biological community are a complex grouping of many different stressors
that individually may not degrade water quality or aquatic habitat, but together can severely
impact aquatic life. Sources of stressors are most often associated with land use in a watershed,
as well as the quality and quantity of any treated wastewater that may be entering a stream.
During naturally severe conditions such as droughts or floods, any individual stressor, or group
of stressors, may have more severe impacts to aquatic life than during normal climatic
conditions. The most common source of stressors is from altered hydrology.

In the fish consumption category dioxin is a stressor resulting in the Impairment of waters in
Albemarle Sound to the mouths of the Chowan and Roanoke Rivers. Dioxins are the byproducts
of industrial processes and are formed during the chlorine bleaching process at pulp and paper
mills. The current dioxin advisory was issued by the Department of Health and Human Services
in 2001. The advisory is for the consumption of catfish and carp in the Albemarle Sound from
58 Water Quality Stressors and Sources
Bull Bay to Harvey Point; West to the mouth of the Roanoke River and to the mouth of the
Chowan River to the U.S. Highway 17 Bridge (Perquimans, Chowan, Bertie, Washington, and
Tyrrell Counties). Women of childbearing age and children should not eat any catfish or carp
from this area until further notice. All other persons should eat no more than one meal per month
of catfish and carp from this area. For more information on this advisory please visit the DHHS
website http://www.epi.state.nc.us/epi/fish/.

6.1.2 Sources

Pollutants fall into two general categories: point sources and nonpoint sources. DWQ identifies
the source of a stressor, point or nonpoint, as specifically as possible depending on the amount of
information available in a watershed. Most often the source is based on the predominant land
use in a watershed. Many point sources were removed from the Chowan River due to the NSW
management strategy with the conversion of municipal wastewater treatment plants to land
application. Stressors sources identified in the Chowan River basin during this assessment
period include agriculture and runoff from WWTP land application sites. In addition to these
sources, many impacts originate from unknown sources.