The potential withdrawal of water from the Mullica River-Great Bay Estuary in southern New Jersey prompted a joint study by biologists and engineers to determine the maximum supply of water that could be diverted from the basin without causing undue environmental impacts. The effect of removal of water from the basin over long periods of time was simulated by review of records of a severe drought. Based on analysis of streamflows and salinities during these drought conditions, minimum mean monthly streamflows were determined corresponding to the maximum salinities tolerable by the fish and shellfish communities, important sources of revenue and recreation in the region. A physically optimized, chance constrained linear programming model was developed for the conjunctive use of ground and surface waters. Adjusting water withdrawal from streamflow and groundwater sources according to physical and seasonal criteria would permit substantial use of the basin's resources, with no additional burden on the ecology of the estuary. (Author)