A goal-programming model to determine the daily production of a seawater desalination plant and the optimal allocation of desalinated water to various blending stations is developed. At these blending stations, desalinated water is mixed with brackish ground water obtained from several wells with different salinity levels. The model constraints are to meet the target levels of demand for blended water, to define the size of the depletion of the nonrenewable ground water, and to ensure meeting the required salinity level. The model objective is to minimize the goal deviations from five priority levels: (1) demands for blended water, (2) control of the salinity levels, (3) depletion of ground water, (4) demands for brackish water at blending stations, (5) and production of desalinated water. The model has been used to determine an optimal allocation for the distribution and blending of desalinated water in the Dammam metropolitan area of Saudi Arabia.