The world is in urgent need of effective international rules to govern the use of freshwater resources shared by two or more states and the resolution of disputes arising from such use. International watercourses — whether rivers, lakes, or aquifers — are unevenly distributed across political boundaries and are increasingly susceptible to depletion and degradation. The increasing shortage of fresh water, coupled with growing consumption demands, have led to inter-state water disputes over allocation and use in practically every part of the world. Moreover, such disputes have proven difficult to resolve due to the complex hydrological and geographical characteristics of fresh water; interconnections with other economic, political, and national security interests; and the relatively weak international legal framework that is currently in place.

First published in 2001, with a second edition in 2007, the third edition of Stephen C. McCaffrey’s The Law of International Watercourses, made available in 2019, addresses the myriad of issues surrounding international watercourses, inter-state disputes concerning their use, and the law governing both. The new edition provides a much-needed update to the previous work, reflecting the important developments that have taken place in the field over the past decade. These include, among others, the entry into force in 2014 of the Convention on the Law of the Non-navigational Uses of International Watercourses (Watercourses Convention)Footnote ¹ as well as recent inter-state freshwater disputes submitted to the International Court of Justice (ICJ)Footnote ² and arbitral tribunals.Footnote ³ In the third iteration of his book, McCaffrey provides a comprehensive analysis of these developments as well as a useful reminder of the fundamental principles and tenets of the law governing international watercourses. The new edition therefore preserves the book’s standing as an authoritative and informative source for students, researchers, and practitioners.

The structure of the book remains largely unchanged from the previous edition, albeit with fourteen instead of fifteen chapters. The chapter omitted was on “International Watercourses as Exclusively National Resources: The ‘Harmon Doctrine’ in United States Practice,” which discussed the origins and status of the “absolute territorial sovereignty” doctrine. This doctrine allows a country to do as it pleases with waters within its boundaries without regard to the interests of other states sharing those waters. It is now discussed briefly in Chapter 4 as one of the “four principal theories” of international watercourse law, although, as McCaffrey notes, it has been debunked both in the practice of the United States and internationally.Footnote ⁴

The focus of the book also remains unchanged: it is the rules of international law governing the non-navigational uses of international watercourses, covering matters such as irrigation, hydropower production, and domestic uses. However, as in the previous edition, the book dedicates a chapter (now Chapter 5) to the navigational uses of international watercourses, with the word “navigation” being used broadly to refer to “the use of a waterway by humans for the floating of any form of vessel, whether crude raft, papyrus boat, sailing craft, steamship, motorized boat, or any other floating conveyance.”Footnote ⁵ Moreover, the focus of the book remains on the rules of international law governing the use of fresh water by states rather than on fresh water itself. Nonetheless, as in the previous edition, McCaffrey dedicates Chapters 1 and 2 to “laying a factual foundation” in order to provide the reader with a “basic understanding of the characteristics of water and of its importance to humanity.”Footnote ⁶ In this regard, Chapter 1 has been updated with a discussion of the growing global water crisis over the past decade, emphasizing the role of climate change, urban population growth, and inefficient water use in this crisis.Footnote ⁷

Another useful addition to the book is the more detailed discussion of the evolution of the law of international watercourses in Chapter 3. Of most interest is the last section of this chapter, which examines the evolution of this body of law from five different perspectives: the prioritization of conflicting water uses (from navigation to no priorities), the conceptualization of water for the purpose of legal regulation (from surface water channel to a system of waters), state approaches to regulating the use of water (from problem solving to integrated management), the protection of water (from protecting fisheries to protecting fish), and the primacy of the obligation of equitable and reasonable utilization (from “no harm” to equitable utilization).Footnote ⁸ In line with the new edition’s focus on recent developments surrounding the Watercourses Convention, the chapter concerning this convention (Chapter 8) has also been updated. It now includes a comparative analysis with the Convention on the Protection and Use of Transboundary Watercourses and International Lakes Footnote ⁹ as well as a discussion of the Watercourses Convention’s coming into force and future prospects.Footnote ¹⁰ At the same time, the book dedicates relatively limited space to a discussion of the evolving human right to water.Footnote ¹¹ A more detailed analysis of this subject, perhaps in a separate chapter, would have been of interest.

With regard to recent developments in the field, both the “Major Cases” and “Selected Case Studies” (Chapters 6 and 7, respectively) have been updated to reflect the rise over the past decade of new inter-state water conflicts as well as the continued intractability of long-standing disputes. The new international cases discussed in Chapter 6 are those concerning the Uruguay and San Juan rivers decided by the ICJ and the arbitral decisions concerning the Indus River, noted above. However, the section on decisions of the Supreme Court of the United States was not updated with more recent inter-state water allocation disputes having now come before that court,Footnote ¹² perhaps because the book was already in press when these cases were heard. The insightful discussion of the leading decisions of this court concerning the American “equitable apportionment” doctrine was retained. However, readers would have also benefited from a more current review of the continued interpretation and application of this doctrine, from which the international water law principle of “equitable utilization” has largely emerged.Footnote ¹³ The case studies included in Chapter 7 remain the same, although some have been updated to reflect recent developments. Most notably, the Nile case study has been updated with a discussion of the Grand Ethiopian Renaissance Dam dispute and the Agreement on the Nile River Cooperative Framework. Footnote ¹⁴ A discussion of more recent developments concerning India and Pakistan’s Indus River dispute,Footnote ¹⁵ as well as of the current renegotiation of the Canada-United States Columbia River Treaty,Footnote ¹⁶ would have also been useful.Footnote ¹⁷

Chapters 9–11 of the book set out the “substantive” obligations of the law of international watercourses — namely, the “equitable and reasonable utilization” and “no-harm” principles and the “obligation to protect international watercourses and their ecosystems.” Chapter 12 then discusses “procedural” obligations, including the obligations to cooperate, notify, consult, and exchange data and information. These chapters continue to provide a valuable introduction to, and discussion of, these fundamental principles. However, the book retains, at least in terms of structure and terminology, the distinction between “substantive” and “procedural” principles. As noted by the American judge on the ICJ in a recent separate opinion,Footnote ¹⁸ and more generally in past and current scholarship,Footnote ¹⁹ a more holistic approach to these principles, which views them as integrated and interconnected, is crucial for their effective application.Footnote ²⁰

Finally, Chapters 13 and 14 of the book, dealing with groundwater and dispute avoidance and settlement, respectively, remain largely unchanged from the previous edition. With regard to groundwater, Chapter 13 now includes a short discussion of the current dispute between Chile and Bolivia concerning the Silala River as well as a review of the International Law Commission’s 2008 Draft Articles on the Law of Transboundary Aquifers. Footnote ²¹ In the context of the Silala River dispute and the definition of “international watercourses” discussed in Chapter 13,Footnote ²² it would have been beneficial to also address the potential implications of the argument, raised by Bolivia, that the river is artificial and therefore not international.Footnote ²³

McCaffrey’s third edition of The Law of International Watercourses is an extremely well written, thorough, and accessible guide to the legal framework governing non-navigational uses of international watercourses, disputes arising from such uses, and their resolution. The book remains an essential source of information and analysis on everything fresh water, written by one of the foremost experts in international water law.