CHAPTER V

ISLANDS WITHIN BOUNDARY RIVERS OR LAKES

A. General Points Islands can be located in many different types of water features. When islands are found in the terri- torial seas or along the coast of a State, the principal issues concern the drawing of baselines. When they are found further out to sea, the principal issues concern whether they generate maritime zones and whether those zones overlap with the maritime zones generated by other features. Both of those situations are addressed in Chapter VI. Yet islands can also be found in areas that are not considered part of the seas, but which are important for inter-State relations. Specifically, islands can be found in lakes and rivers that serve as boundaries between two States. When this happens, disputes may arise as to sovereignty over the island or the relevance of the island for delimiting the boundary. The issues discussed in Chapter IV with respect to sovereignty over islands are applicable as well when addressing islands found in international lakes and rivers, and may speak both to sovereignty over the island and to sovereignty over the appurtenant waters. Islands found in these locations are not addressed through application of any of the rules of the LOS Convention, nor are they subject to dispute resolution under that Convention. Special rules or methods, however, may come into play with respect to islands found in boundary rivers and lakes, which merit at least a brief discussion. 148 S. D. Murphy

B. Islands in Boundary Rivers There exist various contemporary disputes over islands located in boundary rivers, meaning rivers that serve as a boundary between two or more States. For example, there is a small island located at the confluence of the River and the Quarai (or Cuareim) River, where the borders of , , and Uruguay intersect. The island, which is approximately 2 kilometres long and one-half kilometre wide, is known as Brazilian Island, and is claimed by both Brazil and Uruguay, though neither side is actively enforcing its claim 468. Brazil also has a dispute with Bolivia regarding a small island that lies in the Rio Mamoré, called Ilha de Guajará-Mirim by Brazil and Isla Suárez by Bolivia 469. Examples in Europe include disputes between Croatia and Serbia relating to the islands of Vukovar and Sarengrad located in the Danube River 470. Such disputes may principally concern sovereignty over the island (which may then collaterally affect the location of the boundary) or the location of the boundary (which may then collaterally affect sovereignty over the island). In reaching agreement on the location of the boundary, States may choose one of several options : placing the boundary on one or the other bank of the river ; placing the boundary along a median line ; or placing the boundary along the thalweg of the river, meaning a line that follows the deepest channel of the river. The last option has the benefit of providing both States access to the most navigable part of the river, but all these options have the disadvantage of choosing an

468 See Emmanuel Brunet-Jailly (ed.), Border Disputes : A Global Encyclopedia, Vol. 2, ABC-CILO, 2015, pp. 478-479. 469 Central Intelligence Agency, The World Factbook : 2010 Edition, Washington DC, Potomac Books, 2010, p. 82. 470 See Mladen Klemenčić and Clive H. Schofield, “War and Peace on the Danube : The Evolution of the Croatia-Serbia Boundary”, IBRU Boundary & Territory Briefing, Vol. 3 (2001).