Résumé
This chapter introduces the book by exploring the role of water allocation policies in the transition from open to regulated access in the use of water resources. Various allocation approaches and frameworks have developed over time, crafted by water users and communities, and by governments and public authorities. It examines the specific challenges of regulating agricultural water use and implementing water allocation policies in agricultural basins. In this context, the chapter then presents the overall aim of the book and the key dimensions that should be considered when characterising and assessing allocation systems in the context of agricultural water use. The chapter concludes with an outline of the content of the book. In particular, the book is structured in two main sections providing (i) an overview of cross-cutting issues related to the establishment of water allocation systems and (ii) a compilation of 13 chapters presenting water allocation systems across the world.