This paper deals with local irrigation systems organized by villages and communities that existed in the Roman world. It will examine some epigraphic and literary texts and relevant jurisprudential sources belonging to Justinian’s Digest on this topic. In all these cases, the need for joint water use led to the development of at least initial forms of ‘associations’ among so called rivales. These ‘associations’ dealt with different matters such as: a) the distribution of water; b) the regulation of the hydraulic work, such as digging and maintenance; and c) the arbitration of possible disputes between users. For their part, the juridical texts provide a good insight into the ‘legal status’ of these communities, namely how internal relationships between ‘rivales’ were considered.