This article follows the same principal lines as my talk ‘An Irrigation Decree from Roman Spain: the Rivus Hiberiensis’, given at St John's College (Oxford, 19 June 2003), at the kind invitation of N. Purcell and A. Wilson. I am grateful for the observations of those who attended, as well as of those who took part in the seminars held in the Universities of Zaragoza, Genoa, and Eötvös Loránd (Budapest) and in the Spanish School in Rome throughout 2002, and to the numerous colleagues with whom I have had the opportunity to discuss various aspects of this text, among others A. Wilson, A. Lintott, G. Alföldy, and particularly M. H. Crawford, who undertook to translate the inscription into English, and J. N. Adams, who also helped with the translation of various sections; I owe to M. H. Crawford as well many suggestions for supplementing the lost parts of the text. I am grateful also to I. Aguilera, who informed me of the inscription as soon as it appeared, and to the staff of the Zaragoza Museum, particularly its director, M. Beltrán Lloris, for all the help they have given me in studying this inscription. This research has been financed with funds from the Caja Inmaculada Savings Bank's Europa programme and the Grupo de Excelencia ‘Hiberus’ of the University of Zaragoza (Aragon Regional Government). English translation by M. Douch.