A complex mix of local, state, national, and international laws affects the use of groundwater as a source of water supply and as a sink for contaminants. In the United States, states typically have the leading legal role in controlling the use of groundwater (USEPA, 1991). In Europe, a new ground water directive identifi es the role of national governments in responding to both quantity and quality issues of the resource (EU, 2006). In the United States, law basically treats groundwater as a local or state resource. The U.S. federal law does not recognize the emerging understanding that groundwater can migrate across long distances over time and may be essential to streamfl ow in many areas of the country. European Union law recognizes explicitly the relation of ground and surface water in watersheds (EU, 2000). Some U.S. state laws have linked ground and surface water legally to provide conjunctive management. International law dealing with transboundary (cross-border) issues embraces the need to consider the effects on neighboring countries. The framework of state, federal, and case law in the United States indicates who has the property rights in groundwater, the process for dealing with damages incurred by adjacent property owners, who can dispose of contaminants in the subsurface and in what concentration or volume, and who must pay for the cost of cleanup of contaminated groundwater. These legal frameworks provide the basis for economic relationships and exchanges among governments, corporations and individuals which result in the need for economic information and analysis applied to groundwater.