|The prevention of significant harm is an obligation of conduct. Co-riparian states are under the obligation to take ‘all appropriate measures’ to ensure that activities conducted under their jurisdiction do not cause significant harm to the territory of other riparians. States must, for instance, provide prior notification and exchange information with regard to any planned measure that might significantly harm other transboundary watercourse states. This is in contrast to an obligation of result, where states have to reach a fixed goal – sometimes without specification on how to get there.
Taking ‘all appropriate measures,’ then, is an obligation of due diligence in utilisation: ‘a diligence proportioned to the magnitude of the subject and to the dignity and strength of the power which is exercising it [...] and such care as governments ordinarily employ in their domestic concerns’.220 The question which has to be answered here is one of duty of care: What would be expected of a reasonable government in similar circumstances – e.g. enacting necessary legislation; enforcing its laws; preventing or terminating an illegal activity; punishing the person responsible for it? Hence, a state can be deemed to have breached the obligation not to cause significant harm not only when it has intentionally or negligently caused the event itself, but also in case the state did not prevent others in its territory from causing it.221 Some examples of types of measures that should be in place include: establishing water rights; protecting water quality for human and ecosystem uses; setting up a participatory water management structure; establishing a legal system which is coherent at all levels (local, national, international); and setting up the institutional machinery needed to enforce these laws.222
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Equitable and Reasonable Utilisation
Relationship with UNECE Water Convention