Modelling density-induced convection processes in regions containing saline disposal basins

Intercepted saline groundwaters and drainage effluent from irrigation are commonly disposed in natural and artificial saline disposal basins throughout the Murray Basin of southeastern Australia. In this paper, the mixed convection processes which occur below a saline disposal basin are investigated numerically using the 2D model SUTRA. An experimental Hele-Shaw cell analog of a "dry" salt lake is simulated to determine whether SUTRA satisfactorily reproduces density-inducedconvection observed in the laboratory. The model was then applied to Lake Tutchewop, a saline disposal complex in north-central Victoria, using time-dependent boundary conditions for lake salinity and water levels. The calibrated model was then used to predict lake seepage rates, basin stability and sustainability. Concentration profiles and seepage rates from the basin show that Lake Tutchewop is inherently stable under its present operating regime with downward movement of salt mainly controlled by diffusion and dispersion. A sensitivity analysis of governing variables showed that salt fluxes were most sensitive to lake salinity levels.