Surface and groundwater that cross international boundaries present increased challenges to regional stability because hydrologic needs can often be overwhelmed by political considerations. While the potential for paralyzing disputes is especially high in these basins, history shows that water can catalyze dialogue and cooperation, even between especially contentious riparians. There are 263 rivers around the world that cross the boundaries of two or more nations, and untold number of international groundwater aquifers. In order to understand the long term implications of transboundary water management, and the potential for future conflict and cooperation, it is critical to assess what the indicators and triggers are of such processes currently, then evaluate their prospects for the future.