<p>The ecological importance of mill ditches can be confirmed by the results of the mapping of hydromorphology and investigation of fauna and flora at hydropower sites in the Ore Mountains and in Saxon Switzerland (Free State of Saxony). In particular, historic mills and hydropower plants and their hydraulic structures (naturally developed mill ditches, mill dams and weirs) have a high importance as a habitat and a place of retreat for protected species. The integration with the environment is ensured by the historic building structure or the careful restoration of the old structures. Leachate or the discharges of water from the ditches to the river encourage waterlogging and contribute significantly to the preservation or creation of valuable alluvial biotopes. Near-natural mill ditches are not only suitable to establish the link between watercourse and floodplain that the European Water Framework Directive aims to achieve, but also for improving the ecological condition of the water body through their structural richness and biodiversity. A method developed in the pilot project “Lebensraum Mühlgraben” makes it possible to record and evaluate the condition of mill ditches in the low mountain range based on biotope features, hydromorphology and benthic macroinvertebrates.</p>