Many rivers and lakes were selected as boundaries between countries or other political units such as states.
Examples of boundary rivers include the lower Rio Grande River (shared by the U.S. and Mexico), the Rhine River (shared by Germany and France), The Amur River (shared by China and Russia), and the Parana (between Paraguay and Argentina). Lakes shared by multiple countries include the North American Great Lakes, Lake Tanganyika, Lake Victoria, Lake Titicaca, and the Aral Sea. Even more rivers flow across international boundaries from upstream countries to downstream countries.
According to the Transboundary Waters Assessment Programme, 286 rivers are shared by 151 countries, affecting 2.8 billion people, and 42 percent of the world’s land area.
In over 100 of these transboundary river basins, or 38 percent, the countries sharing the rivers have few or none of the key principles of international water law present in their legal framework, and basically no agreement as to how to jointly manage the rivers. Twenty-two transboundary rivers, or 8 percent, mostly in the latter category, are ranked as having “very high” risk for hydro-political tension. This is due primarily to an upstream country developing a project to impound or divert water before it reaches a downstream neighbor. Tensions between upstream and downstream water users have been around since people first started diverting water from streams, in fact, our word “rival” comes from the Latin word “rivalis”, which means “one who uses the same stream as another”.
However, as populations grow, as a warming climate increases evaporative loss, as scarcity of food and water increase, and as other political tensions mount, the likelihood of triggering serious international conflict grows ever more present.
© Colorado State University