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Movement and dispersion of soluble materials in Salem Creek, Muddy Creek, and Yadkin River between Winston-Salem and Salisbury, North Carolina

January 1, 1974

Wastes entering the Yadkin River from the Winston-Salem area, particularly during heavy rains, resulted in several major fish kills in the late 1960's and early 1970's. The actions undertaken to solve this problem, included the collection of data on the time of travel and dispersion characteristics of the tributaries draining the Winston-Salem area and of the main stem of the Yadkin below their confluence.

Fluorescent dye was used to simulate the movement of waterborne wastes under four different flow conditions over a reach of about 41 miles (66 kilometers) beginning at the sewage-treatment plant on Salem Creek and ending on the Yadkin River at High Rock Lake near Salisbury. Total travel time for the entire reach ranges from about 28 hours during periods of high streamflow to about 47 hours during periods of low flow. A soluble substance released as a slug at the sewage-treatment plant disperses longitudinally and laterally as it moves downstream. Longitudinal dispersion, expressed as the time required for a substance released as a slug at the sewage-treatment plant to pass a downstream point, ranges from about 8 hours at the upper end of High Rock Lake during periods of high flow to about 15 hours during periods of low flow. The rate of lateral dispersion also depends on the rate of flow of the Yadkin. During high-flow conditions wastes entering the Yadkin from Winston-Salem disperse across the river in a few miles. Under low-flow conditions lateral dispersion is still incomplete more than 10 miles (16 kilometers) downstream.

Longitudinal dispersion casues the maximum concentrations resulting from slug injections to decrease significantly as the traveltime increases. A relation is presented so the maximum concentration can be estimated at any location downstream from a point of injection at flow rates between about 80 and 500 cubic feet per second (2 and 14 cubic meters per second) at the Muddy Creek gaging station and between about 1,500 and 10,000 cubic feet per second (42 and 280 cubic meters per second) at the Yadkin College gaging station.

Water entering the Yadkin River from Muddy Creek during low-flow periods does not completely disperse laterally for more than 10 miles (16 kilometers) below the confluence, but, when the Yadkin River discharge is above 5,000 cubic feet per second (140 cubic meters per second), lateral mixing is complete within a few miles below the confluence.

Publication Year 1974
Title Movement and dispersion of soluble materials in Salem Creek, Muddy Creek, and Yadkin River between Winston-Salem and Salisbury, North Carolina
DOI 10.3133/wri746
Authors K.L. Lindskov
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Water-Resources Investigations Report
Series Number 74-6
Index ID wri746
Record Source USGS Publications Warehouse
USGS Organization South Atlantic Water Science Center