1 Macroinvertebrate habitat requirements in rivers: overestimation of 1 environmental flow calculations in incised rivers 2 3 Renata Kędzior 1 , Małgorzata Kłonowska-Olejnik 2 , Elżbieta Dumnicka 3 , Agnieszka Woś 4 , Maciej 4 Wyrębek 4 , Leszek Książek 4 , Jerzy Grela 5 , Paweł Madej 5 , Tomasz Skalski 6 5 1 Department of Ecology, Climatology and Air Protection, Faculty of Environmental Engineering and Land Surveying, 6 Agricultural University of Krakow, 30059, Krakow, Poland 7 2 Centre of Research and Science Innovations, 20819, Lublin, Poland 8 3 Institute of Nature Conservation, Polish Academy of Science, 31120, Krakow, Poland 9 4 Department of Hydraulic Engineering and Geotechnics, Faculty of Environmental Engineering and Land Surveying, 10 Agricultural University of Kraków Poland, 30059, Krakow, Poland 11 5 MGGP joint-stock company, 33100, Tarnów, Poland 12 6 Biotechnology Centre, Silesian University of Technology, 44100 Gliwice, Poland 13 Correspondence to: Tomasz Skalski (tomasz.skalski@polsl.pl) 14 Abstract. Flow variability determines the conditions of river ecosystem and river ecological functioning. The variability of 15 ecological processes in river ecosystems gradually decreases. Prediction of the environmental flow allowing to keep biological 16 diversity and river health develops as a response to the degradation of aquatic ecosystems overexploited by humen. The goal 17 of the study was to test the influence of river incision on environmental flow estimation based on the macroinvertebrate 18 BMWP_PL index. The 240 macroinvertebrate assemblages of 12 waterbodies varying in the bed substrate, amplitude of 19 discharge were surveyed in southern Poland. The variations in the distribution of 151 466 macroinvertebrates belonging to 92 20 families were analysed. The similarity of benthic macroinvertebrates reflects the typological division of the rivers into three 21 classes: mountain Tatra streams, mountain flysch rivers, and upland carbonate and silicate rivers (NMDS, ANOSIM, p<0.001). 22 As a response variable reflecting the macroinvertebrate distribution in the river, environmental parameters, BMWP_PL index 23 was chosen. Our results show that the BMWP_PL index reached its highest values in shallower zones (by the shores) and at 24 high water velocity in the Tatra Rivers or low velocity in most lowland rivers. The river incision significantly increased the 25 values of e-flow calculations in relation to redeposited channels. The area of habitat suitability decreased with the bed incision 26 intensity. In highly incised rivers, the environmental flow values are close to the mean annual flow, suggesting that a high 27 volume of water is needed to obtain good macroinvertebrate conditions. As a consequence, the river downcutting processes 28 and impoverishment of suitable habitats will proceed. 29 1 Introduction 30 Human water demand, including irrigation to increase crop productivity, dams, and reservoirs to control the timing of stream 31 flow, and water withdrawal from rivers, has increased dramatically over the last 100 years (Vörösmarty et al., 2010; Veldkamp 32 et al., 2019). Maintenance of a suitable water flow in an active river channel should not only secure human needs, but above 33 all ensure the proper functioning of aquatic ecosystems (Anderson et al., 2006). This has become particularly important since 34 river beds began to be perceived not only as channels filled with water, but as complex ecological systems, in which biological 35 elements play a key role (Poff et al., 1997; Bunn and Arthington, 2002; White et al., 2016). The Water Framework Directive 36 (WFD, European Community, 2000/60/EC) was introduced by European countries to protect and improve the state of aquatic 37 ecosystems and formalize a water flow framework that would maintain this state (Chen and Olden, 2017). 38 Water flow intensity is one of the most important factors influencing multispecies communities of aquatic and water-dependent 39 organisms (Tharme, 2003; Arthington et al., 2006; Higgisson et al., 2019). It is a parameter which shapes the morphology 40 (Michalik and Książek, 2009) and hydraulic flow conditions (water depth, flow velocity) and influences the diversity and 41 https://doi.org/10.5194/hess-2021-196 Preprint. Discussion started: 11 May 2021 c  Author(s) 2021. CC BY 4.0 License.