Traveltime and dispersion in the Illinois River, Marseilles to Peoria, Illinois

Traveltime in 89.3 miles of the Illinois River between Marseilles Dam and Peoria Dam was measured using rhodamine-WT dye. On each of four subreaches, dye-tracer measurements were made at approximately 50and 85-percent flow duration in 1978, 1979, and 1985. The dye-tracer data were used to develop a method for estimating the traveltime and peak concentration of a solute spilled into the Illinois River. The estimates can apply to spills at any point within the study reach during a period of relatively steady discharge of low to medium streamflow. A sample problem to demonstrate the estimating methods is solved for a hypothetical situation in which 10,000 pounds of contaminant is spilled at a railroad crossing between Spring Valley and Hennepin, Illinois. INTRODUCTION The Illinois River is a source of municipal and industrial water supply and is a conveyance for the movement of commerce by barge. Demands for recreation are ever increasing. Consequently, there is a great awareness of the potential for accidental spills of toxic or harmful materials into the river. Streamflow information has been obtained for the Illinois River since the early 1900's, and there are multitudes of publications where data, data summaries, and interpretative information can be reviewed. However, traveltime data for the river are meager and no known publications are available relating to traveltime. The U.S. Army Corps of Engineers operates the structural controls on the Illinois River for navigational purposes. The Illinois Department of Transportation has responsibilities relative to the transportation of hazardous materials on and adjacent to the river. Knowledge of the streamflow and longitudinal dispersion characteristics of the river are needed to facilitate the development of hydraulic models applicable to streamflow regulation and for the control and abatement of accidental spills of pollutants. This report describes results of a study by the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, to measure time of travel and longitudinal dispersion of a reach of the Illinois River between Starved Rock Dam and Peoria Dam. These measurements were combined with measurements between Marseilles Dam and Peoria Dam made in 1978-79 to develop predictive traveltime graphs or relations, The purpose of this report is to describe the procedures used to collect and analyze the traveltime data and to present the techniques by which the user of the report can estimate traveltime and dispersion in the river under a variety of streamflow conditions. The scope of the traveltime relations are for streamflows from 40to 95-percent flow durations, which translates to ranges in streamflow of about 4,000 to 10,000 ft 3 /s (cubic feet per second) at Marseilles and about 4,000 to 14,000 ft 3/s at Peoria. Low-flow and medium-flow measurements, which relate to the above ranges in discharge, were made on eight segments in four subreaches of the river reach from Marseilles Dam to Peoria Dam. The data from the measurements were used to develop predictive relations for traveltime and dispersion at 5-percent increments of flow duration from 40 to 95 percent. DESCRIPTION OF THE STUDY REACH The study reach of the Illinois River was from Marseilles Dam to Peoria Dam, a distance of 89.3 miles. The reach was divided for measurement of time of travel into four subreaches, A to D (fig. 1), ranging in length from 16.0 to 27.3 miles. Figure 1 shows 22 tributaries entering the study reach. The 10 largest tributaries have drainage areas ranging from 49.5 to 2,658 mi 2 (square miles) (Healy, 1979) and are large enough that a storm on a tributary basin could significantly affect the streamflow in the downstream subreacties. Locks and dams at Marseilles, Starved Rock, and Peoria are the only instream structures within the study reach that affect streamflow. The dams are used to maintain water levels sufficient to permit barge traffic throughout the year. Water is diverted from Lake Michigan to maintain streamflow adequate for barge traffic during low-flow periods. Two long-terra, continuous-record, streamflow-gaging stations are located within or near the study reach, one at Marseilles (05543500) and one at Kingston Mines (05568500). The gaging station at Marseilles has 66 years of discharge record showing an average discharge of 10,760 ft 3/s, a maximum discharge of 94,100 ft3 /s, and a minimum daily discharge of 1,460 ft 3 /s. A gaging station just downstream of the study reach at Kingston Mines (05568500) has 46 years of record showing an average discharge of 15,190 ft 3 /s, a maximum discharge of 88,800 ft3 /s and a minimum daily discharge of 1,700 ft3/s. A third gaging station, at Henry (05558300), has only 4 years of record, which is insufficient for reliable statistics. Table 1 lists the river miles for tributaries, dams, active gaging stations, highway and railroad crossings, and river sampling sites along the study reach. All river miles of the Illinois River are measured from its mouth located at the Mississippi River at Grafton, Illinois (Healy, 1979). SUBREACH A 16.0 miles