The Evolution of International Water Law Paulo Canelas de Castro Over the past thirty years International Water Law has undergone profound transformations, real paradigm shifts. The “old” paradigm was based on purely intergovernmental law, minimalist in its obligations, focused mainly on bilateral contracts almost exclusively related to construction projects, quantitative in content and anthropocentric to the core. Its geographical focus also mirrored these minimalist tendencies: so many times it was reduced to boundary waters issues. In such an approach, there is no room for environmental ‘fancies’ nor participation by actors other than the state, and international law is little more than a sum of rights and obligations which lack any purpose or ethical concern. The only identifiable principle is the (economic) principle of equitable use, barely constrained by the vague notion that an effort should be made to avoid damaging neighbouring territory. What is postulated is merely the equitable conciliation of interests. A minimalist law leads to equally weak legal constraints. The Helsinki Rules, adopted by the International Law Association in 1966, are a good illustration of this tendency. Hard law basically consists of treaties, typically bilateral, adopted in Europe and the United States mainly, such as the Luso-Spanish “conventions”. Since the mid-1990s, however, this normative panorama has been experiencing fundamental changes. The first sign was a profusion of international conventions. Amongst them, the following ones particular mention because they represent innovation and indicate new trends: on a global scale, the UN Convention on the Law of Non-Navigational Uses of International Watercourses, adopted in New York in 1997; at the regional level,] the Convention on the Protection and Use of Transboundary Watercourses and International Lakes, adopted in Helsinki in 1992, under the auspices of the UN Economic Commission for Europe; and at sub-regional level, the Convention on Cooperation for the Protection and Sustainable Use of the Waters of the Luso-Spanish River Basins of 1998. This has been supplemented by the activity of numerous international organisations, especially those of the UN family (evidenced by documents such as Agenda 21 or the regulations of the World Bank), and of non-governmental organisations like the International Law Institute or the International Law Association (the Berlin Rules on Water Resources being particularly important). The search is on for new solutions, whether material, procedural, logistical, or organisational for integrated international waters management; a new paradigm. Three main trends seem to evidence its fundamental characteristics. These are the cardinal choices or “friendships”, propensities of a body of law that is no longer axiologically neutral, but governed instead by goals and values in an effort to respond to the global water crisis.