On 18 November, Costa Rica instituted proceedings in the International Court of Justice [ICJ press release] against Nicaragua alleging unlawful “incursion into, occupation of and use by Nicaragua’s Army of Costa Rican territory as well as breaches of Nicaragua’s obligations towards Costa Rica” under a number of international treaties and conventions. The complaint focuses on the incursion of Nicaragua armed forces across the Río San Juan into territory that Costa Rica claims as its own.

According to Nicaraguan President, Daniel Ortega, Nicaragua is merely seeking to restore what is rightfully theirs. As reported in the Tico Times [here], Ortega stated: “In the 1600s and 1700s, the river covered an enormous amount of territory at its delta. And as the zone has dried, the river has moved and (Costa Rica) has continued to advance and take possession of terrain that doesn’t belong to it. The way things are going, if the San Juan River continues to move north and join with the Río Grande of Matagalpa (in the northern zone), that’s how far (Costa Rica) would claim its territory extended.” Ortega further asserted that “Nicaragua has the right to dredge the San Juan River to recover the flow of waters that existed in 1858, even if that affects the flow of water of other current recipients, such as the Colorado River.”The dispute, in fact, can be traced back more than 150 years to the 1858 Treaty on the Boundaries between Nicaragua and Costa Rica, which delimited the border along the Río San Juan. According to the treaty, while the southern bank of the river was declared Costa Rican territory, the river itself was given to Nicaragua. Costa Rica, however, was afforded the right to use the river for commerce.

Following disagreement over the interpretation of the treaty, the two countries agreed to have U.S. President Grover Cleveland arbitrate the dispute. In 1888, President Cleveland concluded (English and Spanish) that the border at the mouth of the Río San Juan lies at Punta de Castilla. Cleveland’s determination was later delineated more precisely in 1897 in the First award under the Convention between Costa Rica and Nicaragua of 8 April 1896 for the demarcation of the boundary between the two Republics.

Despite these rulings, the two countries continued to quarrel over both the location of the border between the two nations and the rights each enjoyed with respect to the use of the Río San Juan. In 2005, the dispute again came to the fore again when Costa Rica instituted proceedings in the ICJ [here] claiming that Nicaragua had unlawfully restricted Costa Rica’s right to navigate and access the Río San Juan by requiring passengers and tourists on Costa Rican vessels sailing on the river to obtain Nicaraguan visas. The ICJ ruled [here] against Nicaragua.

That decision, however, did not prevent Nicaragua from continuing to assert its claims to the river. In recent years, Nicaragua has been dredging older channels of the Río San Juan asserting that the border should follow the river as it flowed back in 1858 when the original Treaty on the Boundaries between Nicaragua and Costa Rica was adopted. Hence, the latest dispute. Interestingly enough, Nicaragua has also been working on a canal to link the Río San Juan and a nearby lagoon, which, at least one new source [Haaretz article] suggests is part of a larger, more ambitious plan by Venezuela, Iran and Nicaragua to create a “Nicaragua Canal” linking the Atlantic and Pacific oceans that would rival the existing Panama Canal.

Notwithstanding, if Costa Rica has its way, the ICJ will focus solely on Nicaragua’s incursion, both its military and engineering activities, on Costa Rica soil. Considering President Ortega’s statements and Nicaragua’s claim to the watercourse as it flowed back in the 1850s, though, Nicaragua will likely challenge Costa Rica’s claim to sovereignty over the territory in question. That challenge will depend, in part, on the interpretation of the relevant treaties and prior determinations. However, taking President Ortega’s statements at face value, international law pertaining to migrating rivers also may be relevant.

Under international law, avulsive changes to a watercourse channel (abrupt changes due to storms and other natural phenomena) do not move a river-based boundary. The international frontier remains in the original channel, even if it no longer carries any water. In other words, countries neither gain nor lose territory when a river marking an international boundary changes its course due to avulsion. In contrast, gradual and natural changes to a watercourse’s channel, such as those produced by natural river flow and scouring, can impact a nation’s geographic range. Under international law, accretive changes can legally increase or decrease a state’s territory, notwithstanding the geographic location of an original river-based boundary. In essence, countries can gain or lose territory when the channel of a river marking an international boundary migrates due to accretion. The river channel, in its new or modified channel, remains the official boundary.

So, is Nicaragua entitled to the river as it flowed in the 1850s? Might they be legally entitled to the land they allegedly invaded? If the ICJ determines that the Río San Juan constitutes the official border, and that the main channel of the river has migrated from its 1858 location, and if the Court concludes that the river moved as a result of avulsion, then Nicaragua’s may have an argument. That, however, will not be easy to establish. Over 150 years have passed since the 1858 treaty. While Nicaragua may be able to produce maps and charts evidencing the channel’s location in the 1850s, establishing that its migration was due solely or predominantly to avulsion is another matter. Over the past decade alone, the region has suffered a number of hurricanes and earthquakes, each of which could have caused the river to move. Yet, over the past 150 years, the region has also experienced more typical climatic condition that could have caused the river channel to migrate in a more gradual fashion. If the river did in fact move from its 1850s location, the reality is that this migration was due to both accretive and avulsive phenomena. Nicaragua certainly has its work cut out. Of course, Costa Rica will have to be ready to disprove Nicaragua’s claims.

You can find additional information on this dispute, including a variety of charts and maps, as well as a discussion of the role that Google Earth has played in stoking the controversy, at Ogle Earth.

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