The Platform for International Water Law and the Dispute over the Status and Use of the Waters of Silala

Laurence Boisson de Chazournes, Professor at the Faculty of Law and the Faculty of Translation and Interpretation and Visiting Professor at the Collège de France, and Mara Tignino, Reaader at the Faculty of Law and the Institute of Environmental Sciences and Lead Legal Specialist to the Geneva Water Hub's Platform for International Water Law acted as counsel for the Republic of Chile in the Dispute over the Status and Use of the Waters of the Silala River before the International Court of Justice (ICJ).

The case was referred to the ICJ by Chile on June 6, 2016, and its judgment was issued on December 1, 2022. This case relates to a river, the Silala, which originates in Bolivian territory and flows into the Antofagasta region of Chile. The river, which has both surface water and groundwater, is located in an arid region bordering the Atacama Desert at an altitude of approximately 4,300 meters. No basin agreement governs Silala, and Chile and Bolivia have not ratified the 1997 Convention on the Law of Non-Navigational Uses of International Watercourses or the Convention on the Protection and Use of Transboundary Watercourses and International Lakes of 1992.

During the written and oral proceedings before the ICJ, both Parties recognized that several provisions of the 1997 Convention, including the principle of equitable and reasonable utilization and the obligation not to cause significant harm, are principles of customary international law and apply to both the surface water and groundwater of an international watercourse such as the Silala. The ICJ recognized the customary nature of these principles and their application to the waters of the Silala.  It also emphasized the importance of cooperation between the two states.  Other principles raised before the Court did not receive the same recognition. The ICJ was reluctant to consider the duty to exchange information on the potential effects of a project on an international watercourse as customary law. According to the Court, there would only be a duty of notification and consultation towards other riparian States concerned when there is "a risk of significant transboundary harm" (para. 114). In a sensitive environment such as that of the Silala, which flows through the desert territory, the risks of potential effects from river use are numerous.  It will be, therefore, important for States to cooperate closely to prevent damage to this sensitive environment.

The judgement is available here

  • slide
  • slide
13 Dec 2022