2.3.1 International Watercourses and Lakes

The already-mentioned Convention on the Protection and Use of International Watercourses and Lakes reflects the modern development of international environmental law, by declaring the principles of precaution, the liability of the responsible and intergenerational justice as leading principles (Art. 2, para. 5), by providing environmental impact assessment (Art. 3) and containing broad cooperation obligation (Art. 9 ff.). Similarly, Convention on the Law of Non-Navigational Uses of International Watercourses, adopted in 1997, is incorporating the principles of balanced ( "equitable"), wise use division, which presupposes a cooperation among the participating States and more detailed provisions on cooperation obligations, as well as the already in the Trail Smelter –case expressed principle of avoiding serious damage. In contrast to the Convention on the protection and use of international watercourses and lakes the precautionary principle is expressed only with regard to the introduction of foreign species. States shall take all necessary measures to ensure the to prevent introduction of foreign or new species into an international watercourse that “may” have adverse consequences for the ecosystem (Art. 22).

Both conventions, however, refer to the principle of sustainability, which basically means a use within the limits of recoverability.