Ground water resources have long been the neglected stepchild of water law. While agreements focusing on transboundary rivers and lakes have been relatively common, there is a paucity of treaties and international norms squarely addressing shared ground water resources. As a result, the rules governing the use, management, and conservation of transboundary ground waters is unclear at best.

This dearth is, in large part, the result of a deficit of scientific understanding among legislators, policymakers, and the judiciary. This is evidenced in many international and domestic laws and policies that have little or no scientific underpinning. Accordingly, there is a significant need to demystify ground water and its relationship to surface water. Moreover, there is a need to inject hydrogeologic concepts and understanding into legal and political discourse and to assist in the development of sound, science-based laws and policies.

In an effort to infuse science into legal understanding, Julio Barberis, in his well-known study, identified four cases where ground water forms part of an international water system. While these cases are generally accepted among legal scholars (including the drafters of the UN Watercourse Convention), the cases are incomplete and imprecise and require refinement to conform to the current knowledge of the science of ground water.

Adapting and building on Barberis's study, the authors propose six models in which ground water resources can have international implication. These models are based on basic hydrogeological principles and actual examples. They are intended to help in the evaluation of the applicability and scientific soundness of proposed and existing rules governing shared ground water resources. Through such analyses, it is hoped that the models assist in the development of clear, logical, and appropriate norms of state conduct.