The dispersal of saline groundwater in the Beaver Creek Diversion System is described using data from a two-year physical limnology monitor of the system. Emphasis is placed on processes influencing temporal and spatial patterns in circulation, stratification and saline water distributions. Owing to its density, the high salinity effluent tends to sink upon entering the reservoir, thus setting up vertical stratification. Wind mixing during the ice-free season is effective only to depths of 4-5 m so that impondment occurs in the deepest portions of the system; however, convective processes in spring and autumn effectively mix the entire water column. Annual variations in salinity and chlorinity are strongly coupled to pumping operations, which increase concentrations, and natural streamflows which decrease concentrations. Overall salt and chloride ion concentrations are highest in Beaver Creek Basin, where effluent enters the system, and progressively decrease toward Spillway Basin where the reservoirs outflow enters Poplar Creek. The time-dependent behaviour of the system is further examined using both a mass budget approach and a 'filling - box' numerical model. Results from these calculations, combined with the field observations, show that the effectiveness of the reservoir as a means of mine effluent disposal is strongly dependent upon the seasonality of natural streamflows. Furthermore, inter-annual variations in flow may be sufficiently large to offset any long term trends. Thus far, disposal operations have not significantly degraded the quality of the reservoir in terms of chloride concentrations.