This book demonstrates what the discipline of economics has to offer as support for analyzing cooperation on management of trans-boundary water resources. It also considers what the discipline of economics has to acquire to become a more effective contributor to trans-boundary water resource management given political legal social physical scientific and ecological realities. This book has its genesis in a symposium of the International Water and Resource Economics Consortium held at Annapolis Maryland April 13-16 1997. The symposium was organized by the editors and the book contains papers presented at the symposium with subsequent revisions. The symposium brought together both economists and agency management personnel for the purpose of discussing not only how economic tools apply to trans-boundary water management but also of identifying the obstacles to making such tools useful and informative to politicians and negotiators in public decision making roles. INTERNATIONAL VERSUS DOMESTIC TRANS-BOUNDARY PROBLEMS Trans-boundary water problems arise in many dimensions. The two most important types of problems emphasized in this book are international and domestic interstate or interregional problems. Cooperation on international problems is especially difficult because enforcement must be voluntary given the sovereignty of nations and the absence of an effective legal enforcement mechanism. Agreements must be sustainable and self-enforced if they are to have lasting benefits. Every negotiating country must be convinced it will receive benefits before it gives its consent to cooperation. In the absence of enforceable agreements trans-boundary (i. e.