As a result of a GEF/World Bank project, all four countries that share the Guarani aquifer (Argentina, Brazil, Paraguay, and Uruguay) have undertaken national reforms to improve the management of this precious groundwater resource. This project now serves as a model for how countries can collaborate on the management of their shared groundwater systems. In May 2003, all four aquifer states agreed to initiate a project called the Environmental Protection and Sustainable Development of the Guarani Aquifer System. The long-term objective of the project is to develop an integrated plan for the protection and sustainable management of the aquifer system. The project has supported the four countries in the joint elaboration and implementation of a common institutional, legal, and technical framework for the management and preservation of the aquifer.