During the Montana Constitutional Convention of 1889, John Wesley Powell, envisioning a landscape of watershed commonwealths, proposed that Montana adopt watersheds as the boundaries of its counties. The idea did not catch on. Over time, the power of local governments to regulate land use has grown immensely, but the misfit between their political boundaries and environmental policy problem sheds has persisted. As our understanding of ecosystem dynamics improves, however, natural resources management policy is gravitating, once again, to the watershed as an appropriate unit of governance. Many federal and state natural resource management initiatives have come on line in the past five years using watersheds as their primary focus. Yet, these new programs lack coherence and invest inadequate authority in watershed-based units of government. Representing perspectives from law, geography, economics, and anthropology, the authors propose the framework for a model state watershed management law. They conclude that the federal government is ill-equipped to take on the role of comprehensive watershed management czar as it has for pollution control and other environmental programs. Yet, local governments, even if organized around watershed boundaries, are unlikely to provide the platform for effective policy implementation. Rather, the authors propose a multi-tiered governance system linking state, regional, and local units of government through careful distribution of planning responsibilities and policy implementation authorities. Although for many states this framework would introduce a new layer of governance, its superior correspondence to the inescapable realities of ecosystem dynamics makes it worth serious consideration.