In the latest Work Programme 2016-2018 of the Common Implementation Strategy (CIS) of the Water Framework Directive (WFD), the Water Directors of European countries agreed to set up a specific Ad-hoc Task Group (ATG) on best practice and guidance to deal with hydromorphology. In this context, one of the core activities of the Working Group (WG) ECOSTAT of the WFD CIS has been to compare the ecological quality expected by different countries for water bodies impacted by water storage.