Both developing and developed countries constantly face problems related to illdefined property rights in common-pool resource systems. These problems are especially acute in water resource ecosystems. A natural consequence of incomplete property rights is the substitution of market-determined exchange by negotiationdetermined exchange. Water rights in the western region of the United States provide an excellent example. This paper is a case study of the negotiations over a water transfer from

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... alifornia's Imperial Valley to San Diego County in light of the transfer's impact on the inland Salton Sea. We analyze these negotiations as a multi-issue, multi-party, non-cooperative negotiating game. We construct stylized representations of the payoff functions for each party as well as of the physical, economic, and political constraints. To model the default outcome, we assign probabilities to various contingencies that might have arisen had the parties been unable to negotiate an agreement. We calibrate the model to the final agreement * The authors acknowledge assistance from David Sunding, Tom Graff, and Anthony Rossman for many helpful conversations on the details and nature of the actual agreement and on the negotiating process. Richard Howitt provided assistance on the appropriate framework for modeling Imperial Valley farming decisions. Yanay Farja provided background research about the Imperial Valley and The Agreement itself. Jeanie Lerner provided secretarial and editing assistance. We also gratefully acknowledge financial assistance from the Giannini Foundation.