TRAVELTIME AND DISPERSION OF A SOLUBLE DYE IN THE SOUTH BRANCH POTOMAC RIVER, PETERSBURG TO GREEN SPRING, WEST VIRGINIA By Alvin R. Jack U.S. GEOLOGICAL SURVEY Water Resources Investigations Report 84-4167 Prepared in cooperation with the INTERSTATE COMMISSION ON THE POTOMAC RIVER BASIN Charleston, West Virginia 1986 UNITED STATES DEPARTMENT OF THE INTERIOR DONALD PAUL HODEL, SECRETAR Y GEOLOGICAL SURVEY Dallas L. Peck, Director For additional information write to: Copies of this report can be purchased from: District Chief U.S. Geological Survey, WRD Open-File Services Section 603 Morris Street Western Distribution Branch Charleston, West Virginia 25301 U.S. Geological Survey Box 25425, Federal Center Denver, Colorado 80225 (Telephone: (303) 234-5888) CONTENTS Page Abstract.. .............................................................................................. .. 1 Introduction ............................................................................................................................... 1 Description of the reach................................................................................................................ 1 Methods of study........................................................................................................................3 Traveltime determinations........................................................................................................4 Discharge determinations.........................................................................................................4 Traveltime estimation...................................................................................................................4 Dispersion.................................................................................................................................4 Summary................................................................................................................................. 12 Glossary.................................................................................................................................. 12 Selected references..................................................................................................................... 12 ILLUSTRATIONS Page Figure 1. Map showing location of the study reach, South Branch Potomac River, W. Va. .......................................................................................................2 2. Graph of observed time-concentration curves for South Branch Potomac River between Petersburg and Romney, November 1970 study............................................3 3. Graph of observed time-concentration curves for South Branch Potomac River between Romney and the mouth, November 1970 study.............................................4 4-5. Graphs of observed time-concentration curves for South Branch Potomac River, September 1982 study...................................................................................... 5 6-7. Graphs of observed time-concentration curves for South Branch Potomac River, September 1982 study......................................................................................6 8. Graph showing traveltime-distance relationship of leading edge of dye cloud, South Branch Potomac River, Petersburg, W. Va., to the mouth..........................................7 9. Graph showing traveltime-distance relationship of peak concentration of dye cloud, South Branch Potomac River, Petersburg, W. Va., to the mouth.................................8 10. Graph showing traveltime-distance relationship of trailing edge of dye cloud, South Branch Potomac River, Petersburg, W. Va., to the mouth..........................................9 ffl ILLUSTRATIONS CONTINUED Page Figure 11. Graph showing attenuation of unit peak concentration with traveltime for selected discharges, South Branch Potomac River, Petersburg, W. Va., to the mouth..............................................................................................11 TABLES Page Table 1. Table showing information on sites used in study........................................................... 13 2. Table showing traveltime, dispersion, and related data from the studies of November 1970 and September 1982 on the South Branch Potomac River from Petersburg, West Virginia, to the mouth.......................................................................14 FACTORS FOR CONVERTING INCH-POUND UNITS TO INTERNATIONAL SYSTEM OF METRIC UNITS (SI) For the convenience of readers who may want to use International System of Units (SI), the data may be converted by using the following factors: Multiply inch-pound units By____ To obtain SI units________ foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km) square mile (mi2) 2.590 square kilometer (km2) ounce, fluid (fl. oz) 0.02957 liter(L) pint (pt) 0.4732 liter (L) quart (qt) 0.9464 liter (L) gallon (gal) 3.785 liter (L) gallon (gal) 0.003785 cubic meter (m3) cubic foot per second 0.02832 cubic meter per second (ft3/s) (m3/s) mile per hour (m/h) 1.609 kilometer per hour (km/hr) ounce, avoirdupois (oz) 28.35 gram (g) pound, avoirdupois (Ib) 453.6 gram (g) degree Fahrenheit (°F) °C = 5/9 (°F-32) degree Celcius (°C) foot per mile (ft/mi) 0.1894 meter per kilometer (m/km) IV TRAVELTIME AND DISPERSION OF A SOLUBLE DYE IN THE SOUTH BRANCH POTOMAC RIVER, PETERSBURG TO GREEN SPRING, WEST VIRGINIA By Alvin R. Jack ABSTRACT tion during passage of the contaminant. Graphs and data in this report will enable the user to predict Traveltime studies, using rhodamine dyes, were the movement and concentration of a soluble con­ made in 1970 and 1982 on the South Branch Poto- taminant spilled in the study reach for discharges mac River from Petersburg, West Virginia, to the between 70 and 1,500 ft3/s. confluence with the North Branch Potomac River at Green Spring, West Virginia. This report combines the results of two studies: One in November 1970 (Hobba and others, 1972) at Flow-duration at the time of the studies was about mean annual flow, or 32 percent flow dura­ approximately 32 percent in November 1970 and 95 tion, and the other in September 1982 at 95 percent percent in September 1982. flow duration or low flow. Dye was injected instan­ taneously at the head of each subreach. Samples Two studies, at discharges of 110 and 1,230 were collected at the same sites in each study. cubic feet per second, were used to define travel- time-distance relationships. A contaminant takes 386 hours to travel 69 miles from Petersburg, West DESCRIPTION OF THE REACH Virginia, to the mouth of the river when streamflow is 110 cubic feet per second. The contaminant The South Branch Potomac River is 135 mi long would, however, take only 89 hours when stream- and has a total drainage area of 1,487 mi2. The flow is 1,230 cubic feet per second. The traveltime study reach between Petersburg, W. Va., and the data were interpolated and extrapolated for selected mouth is 69 mi long and generally is free flowing discharges from 70 to 1,500 cubic feet per second at and unobstructed by any significant impoundments. the index gage near Springfield, West Virginia. The drainage area at the Springfield, W. Va., index gage (site 10) is 1,471 mi2 (fig. 1). INTRODUCTION Moorefield and Romney, W. Va., at river miles 57 and 31 respectively, are the two principal towns A major concern of surface-water users is the and water users in the study reach. The reach from effect that a contaminant spilled upstream will have Petersburg to Romney is 38.3 mi long and has an on their water supply. The purpose of this report is average fall of 7.6 ft/mi. The reach from Romney to enable water users in the South Branch Potomac to the confluence with the North Branch Potomac River to predict (1) the time of passage of a con­ River is 30.7 mi long and has an average fall of 3.9 taminant and (2) the maximum level of concentra­ ft/mi. 79°00' 78°30' - 39°30' 39°00' EXPLANATION O Site location and number - - State boundary - County boundary A Gaging station NATIONAL GEODETIC VERTICAL DATUM OF 1929 Base reduced from U.S. Geological Survey State base map. West Virginia 1:500,000,1966 Figure 1. Location of the study reach, South Branch Potomac River, W. Va. 90 .Site No. 2 (mile 66.2) T= 1:52 80 QC LU t 70 T = Elapsed time from injection of dye until QC peak concentration, in hours and minutes LU CL CO 60 o QC O 40 2 30 Site No. 3 (mile 58.6) T= 9:07 Site No. 4 (mile 54.0) T= 13:07 , Site No.5 (mile 42.2) SiteNo.6(mile31.8) T= 24:22 T= 35:52 ELAPSED TIME, IN HOURS Figure 2. Observed time-concentration curves for South Branch Potomac River between Petersburg and Romney, November 1970 study (Hobba and others, 1972). METHODS OF STUDY Rhodamine dye was injected instantaneously at the upper end of each subreach. Water samples were collected at selected time intervals at one to six Traveltime Determinations sampling sites for each subreach either by hand sampler or syringe-boat sampler. Locations of the The study reach was divided into subreaches to injection points, sampling sites, river crossings, and (1) shorten the overall sampling time, (2) reduce major tributary inflows are shown in table 1. complications from inclement weather, and (3) reduce the change in discharge at the index station Fluorometeys were used in the field to test each during the studies. Large fluctuations in discharge sample for dye and thus determine the leading edge, during the downstream movement of a contaminant peak concentration, and trailing edge of the dye can cause