If a mass of pollutant is suddenly discharged into a stream, this concentrated mass moves with the stream and at the same time mixes continuously with the water. The mixing process consists essentially of two simultaneous actions: lateral turbulent diffusion and longitudinal convection due to mean velocity. This phenomenon has great practical importance in water pollution control, one of the most urgent tasks being undertaken by hydraulic engineers. The studies include: Initial stage of longitudinal dispersion; Techniques of pollutant ejection; Velocity distribution; Effects of channel configurations; Second-order dispersivity tensor for turbulent flows; Longitudinal dispersion in density-stratified flows; Effects of temporary storage and subsequent slow release on dispersion; and the effects of environmental conditions.