Considering the entire fluvial network of Tyrol and South Tyrol, 81 sampling sites were selected according to the following requirements: (1) degree of hydrological disturbance (undisturbed, residual water, temporal residual water or hydropeaking); (2) type of water regime (e.g. groundwater, glacial, nivo-pluvial); (3) degree of morphological disturbance (either near natural conditions or anthropogenic changed conditions); (4) dominant land use type in the catchment with a total area of 4 ha (either grassland, forest, vineyard/orchard or urban settlement); (5) hormone pollution (based on the location of the sample point - before or after sewage treatment plant, or pesticide suspicion).Hydrological and morphological indicators as well as derived indices are based on a standardized methodical approach: (1) survey of morphological and hydrological stream characteristics using standardised field manual and entry form. The hydrological indicators were identified through flow-duration curves, which represent quantitative characterisation of the streamflow regime and harmonised data provided by local agencies and on-site probes; (2) standardized index calculations, starting with the hydrological index IH and morphological index IM, which were summed up to the hydromorphological index IHM.Further details regarding the methodical approach and its application are explained in the publication resulting from the analysis of this hydromorphological data (see Supplement to).

Requirements for the selection of sampling sites have been chosen and judged by experts on-site and through official data provided by local authorities.Fish data: Fish fauna were investigated in each of the 80 sampling sites by means of standard electrofishing methods (Guidance on surveying the biological quality elements – A1; (Haunschmid et al. 2019).Indices based on the method of Schmölz et al. submitted: Based on the hydrological and morphological indicators, 3 indices, the morphology (IM), hydrology (IH), and hydromorphology indices (IHM), were made to create a holistic picture of the total stream conditions. Each index was ranked from 1 to 5 (very good to bad stream conditions).Hydrological and morphological indicators based on the method of Schmölz et al. submitted: The methodical approach (for more details see Schmölz et. al submitted) is based on European standardisation of the Austrian and Italian methods and it has been tested in the context of an international fish project in 81 stream sections in the European Alps, having homogeneous morphological characteristics. The assessment procedure is composed of a set of 11 indicators, which were selected to evaluate longitudinal and lateral morphological and hydrological conditions. The study used fish data, as well as hydrological and morphological on-site data, pre-existing hydrological data, and expert inputs. The combined information of hydrology and morphology enabled the understanding of the dynamics of watercourses and its effects on fish fauna. Each indicator was ranked from 1 to 5 (very good to bad stream conditions).