Longitudinal dispersion in an open channel determined from a tracer study

Abstract

The modelling of pollution transport processes in open channels requires good knowledge about parameters such as hydrodynamic dispersion, advection and decay rates. These parameters can be determined by tracer studies. The basic output of these studies takes the form of observed time course data for the concentration of injected tracer in sampling profiles. In this study, Rhodamine WT fluorescein dye was used as a tracer. The travel time of the front and tail of the dye cloud and the magnitude of the peak concentration can be additionally derived. Two dye tests were carried out at the Svitava and Svratka rivers in the Czech Republic. These are rivers which are mostly regulated and feature widths ranging from 10 to 25 m. Data were collected from 4 and 5 sampling profiles, respectively, along 16.1-km-long reaches of the rivers. The transport parameters were derived via inverse numerical analysis of the collected data and were compared with values obtained by previously published empirical formulas based on dimensional analysis. The resulting dispersion coefficient was from 7.2 to 9.5 m2/s and showed good agreement with previous studies.