Well before the emergence of the nation-state, the arbitrary political division of a unitary river basin — the area of land drained by a river and its tributaries — led to problems regarding the interests of the states and/or communities located within the basin and the manner in which conflicting interests should be resolved. Geography suggests that, by virtue of its physical unity, a river basin should be developed as a single, indivisible whole, irrespective of political divisions. This is so, because moving water, flowing toward an outlet (or outlets), binds land areas together, and interference with the water and its movement at any point has repercussions elsewhere in the basin. Indeed, the river basin can be considered a common property resource by virtue of the fact that its exploitation by one beneficiary may diminish the benefits enjoyed by all others. From the point of view of economic efficiency, as well, the basin should be treated as a unit; in that way, “a careful inventory of soils, feasibility of irrigation and drainage, values of alternative crops, domestic and industrial water needs, could be factored into a basin-wide model that might…yield an ‘optimal’ pattern of water utilization.” To wit, the situation in international river basins exemplifies the pervasive collective action problem: the pursuit of interests defined in purely individualistic terms would lead to socially undesirable outcomes.