SMIRES is a COST Action addressing the Science and Management of Intermittent Rivers & Ephemeral Streams (coord. T. Datry, INRAE, and G. Singer, University of Innsbruck; http://www.smires.eu). This COST Action had brought together scientists from various research field and stakeholders to develop a European multidisciplinary network for synthesising the fragmented and recent knowledge on temporary water courses, improving our understanding of Intermittent Rivers and Ephemeral Streams (IRES) and translating this into a science-based, sustainable management of river networks. The working group “Prevalence, distribution and trends of IRES” (WG1) has the central role to provide the physical basis of the SMIRES Action. One of the tasks of WG1 w...