Water circulates continuously and seamlessly on Earth with little regard for the boundaries we draw. There are natural boundaries as between land and ocean and surface and subsurface environments, as well as human or demographic boundaries between nations, cultures, and religions. Although considered necessary by societies, these human-created boundaries disrupt natural water circulation, leading to serious water-related environmental problems. The dilemma of how to manage water beyond our boundaries remains, and nations have different ways and means of controlling each form of water, whether...