Article 2

2.1.2 International watercourse

The concept of an ‘international watercourse’, as derived from Article 2(a) and (b), means the Convention applies to ‘watercourse systems’ that cross international boundaries, including major and minor watercourses, their tributaries,101 and connected lakes and groundwater, even when these individual components are entirely located within a single state. According to the International Law Commission’s commentary to the 1994 ILC Draft Articles, components of freshwater systems that may fall under this concept, when connected to one another, include rivers, lakes, aquifers, glaciers, reservoirs, canals, wetlands and floodplains.102 The test to establish whether a watercourse is ‘international’ depends on physical factors, the existence of which can be established by simple factual and geographical observation in the vast majority of cases, and the word ‘situated’ is not intended to imply that the water is static.103Related to this test is the question of what waters of an international watercourse are situated in the ‘territory’ of a state and how the location of the boundary is to be determined, especially when an international river changes its course. The Convention does not answer these questions; the answers are found elsewhere in international law. The determination of boundaries depends on whether a watercourse is successive or contiguous (meaning whether it traverses or forms boundaries between states respectively). If it is successive and there is no existing agreement to the contrary, then the border is said ‘to cross the river along the shortest line connecting the points at which the borders of the opposite states intersect the banks of the river’.104 If the watercourse is contiguous the most common treaty approach is to locate the boundary along the thalweg105 if the river is navigable, and along the median line if not.If the international watercourse changes its course and this change occurs over a long period of time (by accretion and erosion) then the general rule is the territorial boundary of a state changes with the river.106 If this change occurs suddenly (by avulsion), then the general rule is the boundary remains in the original location.107 It is also important to note that even if it is acknowledged that a state enjoys exclusive competence over utilisation of the waters of an international watercourse in its territory, given that water is constantly in motion, it is very difficult to determine which waters are located within the territory of a state and thus applying concepts of territorial sovereignty to watercourses is very problematic – as discussed in Part II.108

During the drafting of the Convention, the ILC’s efforts to deal with the geographic scope of an international watercourse generated a rich record of discussion within the ILC and the sixth Committee.109 The ILC gathered state opinion on whether the concept of an ‘international drainage basin’ should be the appropriate basis for their study. Some states objected to the concept, arguing that it could result in regulation not only of the use of the water, but also of the land territory. 110 Ultimately, the expression ‘international watercourse’ was chosen by the ILC and supported by states. However, leading academics refute the argument that the concept ‘international watercourse’ is less expansive than ‘international drainage basin’, stating that Art 1(1) of the UN Convention ‘applies to uses of international watercourses and of their waters for purposes other than navigation and to measures of protection, preservation and management related to the uses of those watercourses and their waters’.111 This means that the Convention indirectly applies to land-based activities taking place within a river basin to the extent that such activities might be relevant for the use, protection, and management of an international watercourse.112

See Section 2.2 for an example of where an activity carried out within the drainage basin pollutes the international watercourse.

101 The inclusion of ‘tributaries’ is important because analysis of several significant watercourse agreements shows that tributaries are often excluded. See B Bearden, Following the Proper Channels: Tributaries in the Mekong Legal Regime, Water Policy 14 (2012) at 991–1014.

102 1994 Draft Articles at 90. The commentary to the Draft Articles states that some members, ‘expressed doubts about the inclusion of canals among the components of a watercourse because, in their view, the draft had been elaborated on the assumption that a “watercourse” was a natural phenomenon’.

103 Ibid.

104 McCaffery, The Law of International Watercourses at 70.

105 The median line of the navigation channel. McCaffrey, The Law of International Watercourses at 70.

106 See JW Donaldson, ‘Paradox of the Moving Boundary: Legal heredity of River Accretion and Avulsion’ (2011) 4(2) Water Alternatives 155.

107 McCaffrey, The Law of International Watercourses at 72.

108 Ibid at 74.

109 There are a number of key milestones in the deliberation of scope within the ILC and UN General Assembly: 1970- The initial UN resolution; 1976- The ILC survey of country views; 1980- Formulation of the ‘watercourse system’ concept; 1984- Rejection of the ‘system’ concept; 1986- Return to the ‘watercourse [system]’; 1991- Synthesis: the ‘watercourse as a system of surface and underground waters’; redaction of the 1994 Draft Articles; and the final 1997 UN Watercourses Convention. Access to these documents is available at the Online Audio Visual Library of the International Law Association: Convention on the Law of Non-navigational uses of International Watercourses. See JL Wescoat, ‘Beyond the River Basin: The Changing Geography of International Water Problems and International Watercourse Law’ (1992) 3 Colorado Journal of International Environmental Law and Policy 301. See also McCaffrey The Law of International Watercourses at 36-54.

110 For differing state views on geographical scope see the Replies of Governments to the International Law Commission’s questionnaire, UN Doc A/CN.4/294 and Add.1, 1 April 1976. For further commentary, see also Tanzi and Arcari, The United Nations Convention on the Law of International Watercourses: A Framework for Sharing at 51-53.

111 McCaffrey, The Law of International Watercourses, at 37, provides that the concept of drainage basin is functionally equivalent – at least hydrologically to that of the watercourse system.

112 Tanzi and Arcari, The United Nations Convention on the Law of International Watercourses: A Framework for Sharing at 59.

Download Fact Sheets

Scope of the Convention #1

Scope of the Convention #2

Groundwater Systems

Relationship with UNECE Water Convention

Relationship with SADC Revised Protocol


Global Water Facts

global water facts
global water facts

Connect with us

Connect on facebook Subscribe to rss

Supported by

WWF UN Water Law Green Cross IUCN University of Northumbria