A modified integral model is developed to predict the near-field behaviour of negatively buoyant discharges, which are typical of those created when releasing brine from desalination plants into a marine environment via a submerged outfall system. These predictions are compared with available laboratory data and the predictions from other integral formulations, both analytical and numerical. Based on these comparisons, it is evident that the modified model is capable of predicting the effects of the additional mixing noted in previous studies, for the range of initial conditions relevant to a submerged discharge from a desalination facility. The modified model is therefore superior to existing numerical integral formulations in this respect and is reasonably consistent with the predictions from previously published analytical solutions. A critical feature of the modified integral model is the reduction in buoyancy flux of the main flow, which provides a mechanism to account for the influences of additional mixing created by buoyancy induced instabilities on the inner side of the flow.