This paper follows in the wake of the growing attention that the world not only academic, and not only in Italy, has been paying for some time, to the issues related to the sound management of water resources of the planet in general, and to the complex legal and institutional aspects thereof in particular. In this context, an issue of particular relevance is the one connected to the management of water resources common to several sovereign states, not only on the surface, but also those hidden in underground aquifers crossed by the borders among states. Some of these are vast and deep, recharging or non-recharging (fossil aquifers), the latter destined to eventual depletion if intensively exploited. Furthermore aquifers are particularly vulnerable to pollution which is often non-reversible. UNESCO, has estimated that of 273 aquifers shared by two or more countries, only five are currently governed by cooperation agreements among the countries concerned. The development of rules that protect transboundary groundwater and shield them from overexploitation and eventual exhaustion, is one of the key environmental challenges for the international community. The Draft articles on the Law of transboundary aquifers formulated by the UN International Law Commission and endorsed by the UN General Assembly in December 2008, provide a response to the challenge, through rules of customary international law relating to the management of aquifers common to or more states. This is a tool that it is destined to play a leading role in the relations among sovereign states relating to the use of groundwater resources, in recognition of their strategic value, not only national but also global. The analysis sheds light in particular on the similarities, but also on some discrepancies between the above-mentioned Draft articles and the 1997 Convention on the Law of the Non-Navigational Uses of International Watercourses. In particular, attention will be paid to the issue of the sovereignty of States in the matter, which is the subject of seemingly different treatment in the two instruments. In the comparative analysis of the two instruments, attention will also be paid to the decidedly "environmental" slant of the Draft articles above mentioned, compared to the more "utilitarian" approach of the 1997 Convention. The paper will also address the issue of the seeming overlap between the two instruments, with regard to non-fossil waters, which come under the scope of both instruments. The following conclusions emerge from the analysis: (1) the principle of sovereignty in the Draft Articles is not absolute as argued by Prof. McCaffrey, but relative and attenuated. Absolute sovereignty and absolute territorial integrity have nowadays been superseded by the development of customary international water law as reflected in the UN Watercourses Convention, which has served as a model for the Draft Articles, and, in particular, in the doctrine and principle of equitable utilization which permeates both instruments; (2) the UN Convention and the Draft Articles are equally predicated on the limited sovereignty principle. Due to groundwater's vulnerability to pollution and depletion, however, in the Draft Articles the protection and conservation of aquifers attract greater attention relative to the utilitarian functions of aquifers, compared to the UN Convention; (3) some overlap between the two instruments is detectable regarding renewable groundwater resources, as these come within the purview of both instruments. This issue has been raised but not tackled by the ILC Special Rapporteur Yamada, and it remains pending as a result; (4) the author favours developing the Draft Articles into a binding instrument -- like a peer Convention to the UN Watercourses Convention, or a Protocol under the latter -- over the non-binding kind of instrument advocated by Prof. McCaffrey. 1. Caponera, DA (2007) Principles of Water Law and Administration, Taylor & Francis, London, 2nd Edition, 267-268. 2. McCaffrey, S (2009) The International Law Commission adopts draft articles on transboundary aquifers, American Journal of International Law, 10ss. 3. Raya, MS (2009) Transboundary Aquifers: Managing a Vital Resources – The UNILC Draft Articles on the Law of Transboundary Aquifers,UNESCO-IHP. 4. Tanzi, A (1997) La Convenzione di New York sui corsi d’acqua internazionali, Rivista di Diritto internazionale, 974ss.