-Stepped fishways are the most popular solutions to enable the free movement of fish fauna through weirs and dams. Given the flow variation of rivers throughout the year, successful fish migration through stepped fishways relies on the accurate discharge calculation and their modeling under variable scenarios. This study aims to propose a general method for flow and water level calculation of stepped fishways, unifying different findings in specialized literature. To achieve this purpose, the relation defined by Villemonte is used and tested under laboratory and field case studies. This study shows that the hydraulic behavior of a wide range of stepped fishway typologies can be explained based on a single equation, as well as the need of calibration of the coefficients involved in this equation for different subtypes. Furthermore, the proposed method enables the water level modeling under variable boundary conditions, which in turns allows the analysis of stepped fishways hydraulic performance under different river scenarios. The comparison of the hydraulic parameters in the fishways with the physical capacities and preferences of fish will contribute to the fulfillment of their main objective: allow free movement of fish fauna.Keywords: discharge coefficient / flow measurement / vertical slot fishway / pool and weir fishway / nature-like fishway Résumé -L'approche de Villemonte : une méthode générale de modélisation de la performance uniforme et non uniforme dans les échelles à poissons. Les échelles à poissons sont les solutions les plus populaires pour permettre la libre circulation de la faune piscicole à travers les seuils et les barrages. Compte tenu de la variation de débit des cours d'eau tout au long de l'année, la migration réussie des poissons par ces passes à poissons repose sur le calcul exact de la décharge et sa modélisation dans des scénarios variables. Cette étude a pour but de proposer une méthode générale de calcul du débit et du niveau d'eau des échelles à poissons, synthétisant différents résultats de la littérature spécialisée. Pour atteindre cet objectif, la relation définie par Villemonte est utilisée et testée dans des études de cas en laboratoire et sur le terrain. Cette étude montre que le comportement hydraulique d'une large gamme de typologies de poissons en gradins peut être expliqué sur la base d'une seule équation, avec besoin d'étalonnage des coefficients impliqués dans cette équation pour différents sous-types. De plus, la méthode proposée permet de modéliser le niveau de l'eau dans des conditions aux limites variables, ce qui permet, à son tour, d'analyser la performance hydraulique des passes de poissons en escaliers selon différents scénarios de rivières. La comparaison des paramètres hydrauliques dans les passes à poissons avec les capacités physiques et les préférences des poissons contribuera à la réalisation de leur objectif principal : permettre la libre circulation de la faune aquatique.Mots-clés : coefficient de décharge / mesure de débit / passe à fentes vert...

4Vertical slot fishways are a type of fish pass of wide operating range that allows fish to move 5 across obstacles in rivers. This study aims to model the performance of these structures, under 6 uniform and non-uniform flow conditions, using discharge coefficients involving the 7 downstream water level together with a logical algorithm. This will allow to explain the 8 hydraulic behavior of this type of fishways under tailwater levels and flow variations on 9 rivers. Two vertical slot fishways located in Duero River (North-Central Spain) subject to 10 different hydraulic conditions were studied for the validation of the proposed formulation. 11The observed values are consistent with the predicted results and, among others, demonstrate 12 the importance of including variables which consider downstream water level. Consequently, 13 the proposed discharge coefficients together with the algorithm have resulted in a method 14 which enables to improve the performance of both existing and future vertical slot fishways. 15 This will have major implications in real-life scenarios where uniform operation conditions 16 are rarely achieved. 17 2012). 126 127 Fig. 2. Flowchart showing the steps of the proposed algorithm. Note: The symbols are defined 128 in the notation section. 129 Validation 130The fit of the proposed discharge equations was evaluated using r-squared (r 2 ) with data 131 collected both from the specialized literature and field measurements (Fig. 3). The 132 comparison of the predicted water depth profiles using the algorithm and each of the adjusted 133 equations was carried out by comparing the mean relative errors (MRE) for each scenario.

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With the aim of building more compact fishways and adapting them to field conditions to improve their location by fish, it is common to use turning pools, reducing the longitudinal development of the construction. However, depending on their design, turning pools may affect the hydraulic performance of the fishway and consequently the fish passage. To study these phenomena, turning pools in a vertical slot and in different configurations of submerged notches with bottom orifice fishway types were assessed. Both types of fishways were studied using numerical 3D models via OpenFOAM, a computational fluid dynamics software, in combination with fish responses, assessed with PIT (Passive Integrated Transponder) tag telemetry for three different species of potamodromous cyprinids in several fishways. Results show differences between the hydrodynamics of straight and turning pools, with lower values in the hydrodynamic variables in turning pools. Regarding fish behavior, the ascent was slower in turning pools but with no effect on passage success and without being a problem for fish migration. This information validates the use of turning pools as a key design component for fishways for studied species.

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