Four Countries Strengthen Guarani Aquifer Cooperation

Beneath the territories of Argentina, Brazil, Paraguay and Uruguay lies one of the world’s largest transboundary groundwater systems. The Guarani Aquifer System (GAS) supports water supply, ecosystems and productive activities across the region. But sharing a resource of this scale also presents a challenge: building a common knowledge base and establishing mechanisms to manage it beyond national borders.

Over the past years, Argentina, Brazil, Paraguay and Uruguay have made significant progress in this direction with the support of the Global Environment Facility (GEF), CAF – Development Bank of Latin America and the Caribbean – and UNESCO. Through the project “Implementation of the Strategic Action Programme for the Guarani Aquifer System: Enabling Regional Actions” (PPM-Guaraní), GEF financing and regional cooperation have helped translate shared priorities into concrete tools to monitor the aquifer, exchange information, strengthen capacities and jointly guide its sustainable management.

One of the project’s most significant achievements was the establishment of the first Regional Monitoring Network for the Guarani Aquifer System, initially comprising 35 wells distributed across the four countries. The network operates under harmonized protocols to monitor groundwater quality and quantity and is linked to an Information Exchange System, enabling participating institutions to share scientific data that can support better-informed decision-making.

But building shared management requires more than data. During project implementation, more than 2,000 people participated in workshops, training activities and dialogue spaces across Argentina, Brazil, Paraguay and Uruguay, including representatives from national and local governments, the scientific community, water users, civil society organizations, Indigenous Peoples, the private sector and academia. The process also generated more than 20 new technical documents that remain available to the countries and contributed to strengthening regional governance mechanisms. Among these mechanisms, the project established and operationalized two multinational technical committees with representatives from all four countries and gender parity criteria in their composition: the Monitoring and Modelling Committee (CMM), operational since December 2022, which supports data exchange and monitoring strategies; and the Capacity Building and Outreach Committee (CCD), operational since April 2023, which supports regional coordination on capacity building and knowledge dissemination.

This combination of science, institutional cooperation and participation led to another of the project’s key legacies: the update and approval of the Strategic Action Programme for the Guarani Aquifer System (SAP 2025). Developed through a technical and participatory process involving the four countries, the updated SAP translates the project’s lessons and achievements into a shared roadmap for continued regional cooperation.

The roadmap is structured around eight strategic programmes and 25 regional actions, covering transboundary cooperation, the maintenance and expansion of the monitoring network, scientific knowledge generation, social participation, capacity development, local management and responses to climate impacts. In this way, the conclusion of PPM-Guaraní does not mark the end of the process, but rather provides a foundation for its continuity.

The project’s legacy demonstrates how cooperation around transboundary waters can move from agreements to action: shared data, common protocols, strengthened capacities, coordination mechanisms and a jointly developed regional agenda. For Argentina, Brazil, Paraguay and Uruguay, protecting the Guarani Aquifer System also means strengthening their shared responsibility for a strategic resource for present and future generations.

Words by: Alicia Montalvo, CAF – Development Bank of Latin America and the Caribbean; Lina Mandragón, CAF– Development Bank of Latin America and the Caribbean, Ignacio Lorenzo; CAF – Development Bank of Latin America and the Caribbean