The mechanism of migration of high-density solutions injected into fresh water was studied in the laboratory by physical models. Fifty-four laboratory tests were performed using a sand box constructed of transparent plastic. This physical model represented a portion of the groundwater flow. A high-density flow was simulated using solutions of various densities and chemical composition. It was found that migration of high-Density solutions in ground water is in many instances governed by the relation between the density of high-density solution and that of the ground water. Peculiarities of temporal and spatial contaminant distribution in the dispersion halo, the effect of filtration flow velocity, the relationship of flowrates between the fresh-water and contaminant flows, and the impact of the model boundaries and gravity were determined. Dependence of the dispersion haloes shape upon the structure of the fresh-water flow is described. The paper examines migration of low-density solutions over high-density solutions and the behavior of high-density solutions under conditions of discharge at the surface. The results show that the migration of high-density solutions is distinctly three-dimensional, and its prediction is possible only when based on three-dimensional numerical models.