Document Type



This Article begins with an overview of the ecology of the Guarani Aquifer region before turning to the legal and ecological problems it faces. Because the majority of the Guarani Aquifer underlies Brazil (with the rest residing below Argentina, Paraguay, and Uruguay), the laws and policies of Brazil have a significant managerial impact. Consequently, the Brazilian legal regime forms the focus of the first Part of the Article. The Article then analyzes the international transboundary framework before turning to the recently enacted Agreement on the Guarani Aquifer. This Agreement, signed but not yet ratified by four countries, represents a major step forward in transnational cooperation. However, its language is so broad that it elides some of the principal management challenges facing this and all transboundary aquifers. The Article then looks at the legal and policy issues that local environmental problems and climate change present for the management of the aquifer and recommends a management and dispute resolution strategy based on the notion of “equitable apportionment.”

The complexity and environmental importance of the region, as well as the looming threats presented by climate change, make the need for accurate and detailed scientific and technical information urgent and crucial. Yet, relying on such information to manage such a complex natural resource also presents risks. Too often, the role of uncertainty in risk assessment and in legal and managerial decisions gets reduced or ignored. Lessening uncertainty requires reducing asymmetric information. The recent international agreement regarding the Guarani represents a significant (albeit preliminary) step forward in this regard. Increasing knowledge over the regulated resource demands categorizing “hard” and “soft” uncertainties. In addition, the regulatory framework must acknowledge the unitary nature of the aquifer while yet remaining sensitive to differing national and local priorities. This Article reviews the endogenous and exogenous challenges facing the Guarani Aquifer System. It looks particularly at those within and arising from Brazil. It then offers an international dispute resolution framework, drawn from the United States’ doctrine of equitable apportionment, and offers some proposed amendments to the multilateral agreement for managing the Guarani.