The nature of flow in stratified reservoirs has been studied and a method developed, based on a laboratory model study, to predict the quality of the water discharged from the reservoir. The experimental data has been evaluated in dimensionless form, so that the results may be applied to actual reservoirs. The model was designed to simulate a relatively high head dam impounding a stratified reservoir in which the density gradient is approximately linear. The extent and magnitude of internal density currents can be determined, and the properties of the discharged water can be predicted from measurements of flow rate, density gradient, and depth. The temperature of the discharged water, effect on downstream environment, and change in the thermal structure of the reservoir are among the quantities which may be forecast. Illustrations have been provided to show the degree of control of water quality available by regulation of the reservoir water discharge.