The effects of channel
excavation on water-quality characteristics of the Black River and on
ground-water levels near Dunn, North Carolina
Water-Resources Investigations 82-4083
By C.E. Simmons and S.A. Watkins
Abstract
During 1976-81 data were collected at three sites on the Black
River near Dunn, N.C., to define the effects of channel
excavation on stream quality and on ground-water levels in
nearby areas. One of the data sites was located upstream from
the five-mile long excavated reach and served as a background
station. Changes in various characteristics of this Coastal
Plain stream were determined by comparing data collected before,
during, and after the construction period. After deepening of
the channel by more than 2 feet, ground-water levels within 100
feet of the stream declined a proportionate amount; however,
levels in a well 500 feet from the stream were unchanged. Flow
velocities during channel deepening were 100 percent higher than
velocities prior to construction. An average increase in water
temperatures of about one degree Celsius was observed following
removal of trees and brush that provided shading to the stream.
After construction, concentrations of dissolved oxygen also
increased. The percent of saturation increased 20 to 25 percent
in the lower values. Maximum concentrations of suspended
sediment increased from about 75 mg/L prior to construction to
over 2000 mg/L during construction. Within a year after
construction, levels of suspended sediment during stormflow had
decreased but remained 5 to 10 times greater than
preconstruction levels. Little or no change occurred in pH,
total-dissolved solids, nitrogen, phosphorus, and bacteria.
Citation:
Simmons, C.E., and Watkins, S.A., 1982, The effects of channel excavation on water-quality characteristics of the Black River and on ground-water levels near Dunn, North Carolina: U.S. Geological Survey Water-Resources Investigations 82-4083, 28 p.
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