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V diplomskem delu so prikazani razlogi za gradnjo ribjih stez, vrste ribjih stez, ribja steza ob HE Arto Blanca, možnost njene optimizacije in analiza ihtiološkega pregleda s pomočjo hidravličnih vrednosti v ribji stezi. Ribje steze se gradijo za ohranjanje biološke povezanosti vodotoka pod in nad pregrado , ker je z gradnjo pregrade ta povezava prekinjena. To prizadene zlasti migratorne vrste rib in druge vrste organizmov, ki za svoje dolgoročno preživetje potrebujejo različne življenjske prostore. Predstavljen je problem ribje migracije na spodnji Savi v Sloveniji. Seznanimo se z ribami, ki tam živijo, in s plavalnimi sposobnostmi nekaterih najpogostejših rib v tem delu reke. V nadaljevanju so predstavljeni najpogosteje uporabljeni ribji prehodi. Določeni tipi ribjih prehodov so ustrezni le za določene vrste rib in vrste ovir. Leta 2009 je bila zgrajena ribja steza ob HE Arto Blanca, ki je ena redkih dobro delujočih ribjih stez na velikih pregradah v Sloveniji. Predstavljeni so njeni deli in način obratovanja njenega vtočnega odseka. Sledi prikaz optimizacije ribje steze s programom PCFLOW2D, ki ima možnost upoštevanja k-ε modela turbulence za nestalni tok. Kot osnovna geometrija je bila vzeta geometrija dela vtočnega odseka (ki je izveden kot bazenski tip z vertikalnimi režami) obstoječe ribje steze ob HE Arto Blanca. Ugotovljeno je bilo, da se s premikanjem reže med prekati proti sredini prekata zmanjšujejo maksimalne hitrosti in območja z izrazito veliko disipacijo turbulentne kinetične energije ε, zato pa se manjšajo območja z izrazito majhnimi hitrostmi in ε. Prav tako je bilo ugotovljeno, da v ribji stezi z vertikalnimi režami ni velikih sprememb parametrov ob spremembi pretoka, spreminja se le gladina vode. Na koncu so rezultati ihtiološkega pregleda ribje steze ob HE Arto Blanca ovrednoteni z rezultati optimiziranih hidravličnih vrednosti v ribji stezi. Ugotovljeno je dobro delovanje obstoječe ribje steze. This thesis deals with types of fishways and reasons for building them. It focuses on the fishway at HPP Arto Blanca, the possibilities for its optimization and the analysis of the ichthyological review based on the hydraulic data found in the fishway. Fishways are built in order to prevent interruptions of a watercourse which may occur when an obstacle is constructed. Especially migratory species of fish, but also some other organisms that depend on different habitats for their long-term survival, can be affected by such interruptions. The problem of fish migration in the lower section of the Sava River in Slovenia is presented. Species of fish living there and their swimming abilities are also described. This is followed by the description of the most frequently used types of fish passes. Certain types of fish passes are suitable only for certain types of fish and specific types of obstacles. The fishway at HPP Arto Blanca was built in 2009 and is one of the few well-functioning fishways on large dams in Slovenia. Its structure and the operation mode of its inlet section are discussed. The optimization of the fishway is then analyzed using the program PCFLOW2D and the k-ε turbulence model for unsteady flow. The geometry of a part of the inlet section of the existing fish pass at HPP Arto Blanca (implemented as a swimming pool type with vertical slots) served as a basic geometry. It was determined that, by moving the slots between the pools toward the center section, the maximum speed and areas with markedly high dissipation of turbulent kinetic energy ε are reduced. Consequently, areas with markedly low values of velocity and ε decrease. It was also found that a change in discharge causes no major parameter changes in the fishway with vertical slots. The only change observed is in the water level. Finally, an evaluation was performed, comparing the results of the ichthyological review of the fishway at HPP Arto Blanca with the results of the optimized hydraulic values in the fishway. The existing fishway was found to be well functioning. |
