Environmental effects of water derivations on watercourses in Catalonia

Watercourses are often impacted by hydraulic infrastructures and water withdrawals. It has been demonstrated that these alterations affect the availability of habitats for aquatic species. Consequently, it is necessary to define a method to quantify the effects on the species and to define the proper e-flow level required to ensure the conservation of the biodiversity and the ecological services provided by the rivers. Therefore, for the e-flow definition, the Meso-HABSIM methodology (Mesohabitat SImulation Model) [1, Parasiewicz, 2001] is adopted in Italy. It is a well-established method for the river habitat modelling, designed to assess the spatial and temporal habitat availability for fish fauna. This methodology operates at the mesoscale, through the combination of the hydraulic and geomorphic units, describing both the physical and biological characteristics of the river. The parameters employed are current velocity, water depth, substrate type, and presence of refugees or cover. Furthermore, a crucial phase is the creation of a biological model based on the random forest method, an accurate machine learning technique. These models define the suitability of river habitat to host target species, based on the environmental existing conditions. The purpose of this thesis project is to assess the impact of flow alteration on the rivers Aigua de Valls and Foix in Catalonia region (Spain) exploiting the Meso- HABSIM methodology. This research is a part of a larger initiative commissioned by the ACA (Agència Catalana de l’Aigua), that involves a larger number of rivers. The main purpose is to perform an assessment of the environmental flows and, if needed, to make adjustments for future planning cycles. The study has been carried out on ten different rivers, subjected to a flow alteration; the dataset used to develop the biological models for native Catalan species have been collected in natural rivers. The work of this thesis includes field work and data processing. The field data collection activities on the Aigua de Valls and Foix rivers have been carried out between June 2021 and February 2022. During the period between April 2021 and February 2022, the data needed to develop the biological models for each season have been collected on different rivers all around Catalonia.