Article 7

7.1 Commentary

The obligation ‘not to cause significant harm’ also derives from the theory of limited territorial sovereignty. According to this principle, no states in an international watercourse are allowed to use the watercourses in their territory in such a way as to cause significant harm to other watercourse states or to their environment, including harm to human health or safety, to the use of the waters for beneficial purposes, or to the living organisms of the watercourse systems. This principle is widely recognised and incorporated not only in modern transboundary water agreements, but also in international environmental law. However, the question remains about the definition or extent of the word ‘significant’ and how to define ‘harm’ as a ‘significant harm’. It is also important to note that, contrary to popular belief, in some cases ‘harm’ can be caused by a downstream state to its upstream riparian – i.e. by foreclosing the upstream state’s future water uses through the prior utilisation of such water.’219

219 See SMA Salman, ‘Downstream Riparians Can Also Harm Upstream Riparians: The Concept of Foreclosure of Future Uses’ (2010) 35 Water International 350.

The evolution of the ‘no significant harm rule’

1938 Trail Smelter Case | ‘Good Neighbourliness’

[N]o state has the right to use or permit the use of its territory in such a manner as to cause injury by fumes in or to the territory of another […] when the case is of serious consequence and the injury is established by clear and convincing evidence.

1972 Stockholm Convention | Principle 21

States have […] the sovereign right to exploit their own resources pursuant to their own environmental policies, and the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other states or of areas beyond the limits of national jurisdiction.

1985 Vienna Convention for the Protection of the Ozone Layer | Article 2(1)

The parties shall take appropriate measures […] to protect human health and the environment against adverse effects resulting or likely to result from human activities which modify or are likely to modify the ozone layer.

1992 Biodiversity Convention | Article 3

1992 Rio Declaration | Principle 2

States have […] the sovereign right to exploit their own resources pursuant to their own environmental and developmental policies, and the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other states or of areas beyond the limits of national jurisdiction.

1992 UNECE Helsinki Convention | Article 2(1)

The Parties shall take all appropriate measures to prevent, control and reduce any transboundary impact.

1997 UN Watercourses Convention | Article 7(1)

Watercourse states shall, in utilising an international watercourse in their territories, take all appropriate measures to prevent the causing of significant harm to other watercourse States.

Video: Alistair Rieu-Clarke What is the relationship between the Principle of Equitable & Reasonable Use and the No-Significant-Harm Rule in the UNWC?