Author(s): Il Won Seo; Hwang Jeong Choi; Young Do Kim; Eun Jin Han; Hyun Saing Mun
Keywords: Dispersion; Two-dimensional stream-tube routing procedure; Tracer concentration; Rhodamine WT; Gam stream
Abstract: Dispersion characteristics of pollutants should be well understood to deal with water pollutant problems in natural streams. Physically, dispersion, which is the spreading out of pollutants across and along stream, arises due to the combined effect of the differences in velocity and turbulent diffusion. In a mathematical model, the dispersion term appears when the three-dimensional advection-diffusion equation is transformed into the two-dimensional advection-dispersion equation by integration with respect to depth. For the application of the two-dimensional numerical model, the suitable selection of the dispersion coefficient, which is one of the primary parameters of the model, is very important. In this research, a two-dimensional stream-tube routing procedure was applied for evaluating both the longitudinal and transverse dispersion coefficient. In the routing procedure, the dispersion coefficients are calculated by matching the predicted tracer concentration routed from the upstream observation to the downstream observation of the tracer cloud passage. To acquire the tracer data, we conducted the two-dimensional tracer tests using a Rhodamine WT as tracer at Gam stream–the tributary of the Nakdong River system in Korea. At each test reach, three sections (lateral lines) were installed using a hose which was fixed on wooden piles located at both banks. These lateral lines were set up perpendicular to the flow direction. Using these later lines, the hydraulic and concentration data were collected.