States are geopolitical entities in which a governments claim control over defined territories. Today, the predominant view of Earth is of a planet divided by imaginary political boundaries. There are, however, real and natural boundaries that exist in the world. For instance – the boundaries of drainage basins, or watersheds, which are geographic areas where surface water flows downstream to a single point. Watersheds are a type of bioregion, or naturally defined area. Folks often recognize the geographic shape of their state, but rarely do they know the boundaries of their watershed.
Source: World-wide Hyrdrogeological Mapping and Assessment Programme