Ground-water quality in the Piedmont and its affect on the Neuse River
Seventh Annual Neuse River Foundation Symposium Proceedings
By Douglas A. Harned
Abstract
Ground-water discharge is the primary source of the water flowing in
the Neuse River during periods of low flow. By comparison, waste-water
discharge accounts for only around 15 percent of the low-flow discharge.
Annually, around 40 percent of the flow in the Neuse River upstream from
Clayton, in the Piedmont province, is ground-water discharge.
In the Piedmont, the ground-water flow and surface-water systems are
connected. Consequently, contaminated ground-water may eventually discharge
to streams that are water-supply sources. Because perennial-stream drainage
basins in the Piedmont are generally smaller than 1 square mile, it is
generally thought that the distance between the point where a drop of water
or waste enters the ground-water system is commonly less than a half mile
from where that drop may eventually discharge to a stream. The perennial-
stream drainage basin is essentially a complete flow-system cell, similar to
and yet hydrologically separate from surrounding drainage-basin cells.
The quality of ground water that discharges into the Neuse River has a
direct effect on quality of the river. In general, estimated concentrations
of major dissolved substances tend to be greater in the ground water than in
the river water that includes a mix of ground-water discharge and surface
runoff. Ground-water quality is affected by rock and soil composition and
land use. To test these relations, and to compare ground-water quality with
water quality in streams at low flow, soils, rock type, and land-use data
were compiled for 1,800 wells in the Piedmont of North Carolina.
Concentrations of dissolved solids and chloride are generally higher in
ground water sampled from wells near landfill and industrial land uses than
from commercial, residential, and farm or forested areas. Concentrations of
dissolved nitrate sampled from wells near farm and commercial land uses are
often much higher than the 0.5 milligrams per liter generally thought to
allow abundant algal growth in surface water. If reductions in nitrate are
included in a plan for controlling eutrophication in the Neuse River, then
the contribution of nitrogen from ground water will have to be taken into
account.
Citation:
Harned, D.A., 1987, Ground-water quality in the Piedmont and its affect on the Neuse River: Seventh Annual Neuse River Foundation Symposium Proceedings, November 12-13, 1987.
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