When water resources are shared by two or more autonomous political entities, the timing and magnitude of the respective individual uses have been continual sources of conflict. Recognizing the need for clear standards and principles for effective and efficient water sharing, ASCE's Task Committee for the Shared Use of Transboundary Water Resources (SUTWR) reviewed existing transboundary agreements to develop a series of model codes to limit the potential for conflict while providing an appropriate balance between efficient use of the water resource for economic purposes, public health, and ecological protection. Because of the nature of sovereignty and its attendant limitations for full efficiency in water use, three model agreements were developed for use according to the degree of willingness of the parties to forgo sovereignty. All three models - Coordination and Cooperation, Limited Purpose, and Comprehensive Management - focus on the allocation and use of shared waters and on resolving conflicts involving such waters. These three water sharing agreements can be used directly within the United States context and may be used with minor alteration in the international context.