Authenticity, in the sense of credibility or truthfulness, is one of the key categories in heritage management. This paper focuses on the question of authenticity in relation to industrial heritage, specifically water management structures. In the case of these structures, emphasis is usually placed on authenticity of function, but two further types of authenticity are equally important: authenticity of material substance or form (in relation to the original design and the structure built on its basis), and authenticity as a consequence of historical evolution. The paper presents an analysis of four model examples of water management structures that are either legally protected heritage sites or have been proposed as candidates for legal protection. The analysis of their heritage values provides insights into the individual categories of authenticity and enables the formulation of principles for managing sites of heritage value.