Ocena prehodnosti prečnih vodnih objektov na reki Bači glede na mobilno sposobnost rib

Ferjančič, Kim (author), Toman, Mihael Jožef (mentor), Kryžanowski, Andrej (comentor)

Na reki Bači smo evidentirali in popisali 79 prečnih vodnih objektov s potencialnim negativnim vplivom na gorvodno prehajanje rib. Med njimi je bilo 13 hidroenergetskih objektov in 1 ribja steza, za katero smo v času meritve ocenili kot neprehodno za vse ciljne vrste rib. V okviru terenskega popisa smo ocenili tudi stanje objektov, največ je bilo delno poškodovanih, in sicer jih je 28 imelo poškodbe z obsegom med 10 % in 30 %. Prehodnost objektov smo ocenjevali s francosko posredno metodo točkovanja in razvrščanja ICE. V času nizkega pretoka smo izmerili izbrane geometrijske in hidravlične parametre ter objekte razvrstili v skupine: ROCK, VERT, INCL, CPLX-FALL in STEP. Znotraj posamezne skupine smo s pomočjo večstopenjskega kriterija primerjali meritve parametrov s teoretičnimi mejnimi vrednostmi, ki smo jih določili glede na skakalne in plavalne sposobnosti posamezne vrste ribe. Vsakemu objektu smo izračunali enega izmed 5 razredov prehodnosti: 0; 0, 33; 0, 66; 1; NC. V povprečju je bilo za vse vrste rib največ prehodnih mest v skupini kamnitih drč (ROCK). Višinska razlika med koto zgornje in spodnje vode na objektih je bila 0,1-8 m. Za reofilne krapovce je bilo prehodnih 24 % vseh objektov, za kaplja le 14 %. Ocena prehodnosti za lipana (59 %) in jadranskega lipana (51 %) je bila manjša od večjih postrvi. Najvišjo oceno prehodnosti smo izračunali za tujerodno šarenko (65 % prehodnost). Z rezultati ocene prehodnosti smo tako potrdili, da je vzdolžna povezanost reke Bače prekinjena vzdolž celotnega vodotoka, kar kaže tudi podatek, da so v povprečju na kilometer struge zgrajeni 3 pragovi.

• Language: Slovenian
• Keywords: vzdolžna povezanost vodotoka, prečni vodni objekti, prehodnost, ribe, premiki
• Work type: Master's thesis/paper
• Organization: BF - Biotechnical Faculty
• Year: 2019
• PID: 20.500.12556/RUL-106029
• COBISS.SI-ID: 4987215
• Publication date in RUL: 17.01.2019

Secondary language

• Language: English
• Title: Fish passability assessment of transverse water obstacles in Bača River

Abstract

We measured 79 transversal water obstacles with potential impact on the upstream passage of fish in Baca river. There were 13 hydropower plants among them and only 1 fish-pass, which were assessed as non-passable for all target fish species. We also included the state of the obstacles in the field survey, determining most of them as partially damaged (with a damage range between 10-30 %). For the assessment of fish passability, we used indirect scoring and classification ICE method (protocol), based on a comparison of the typological, geometric and hydraulic characterisrics with the swimming and jumping capabilities of the fish species analysed. All objects were ranged in groups regarding the ICE protocol. We assessed the passability using the multi-stage criterion based on comparison of measured and calculated threshold characteristic value, and classify objects into one of 5 passability classes: 0; 0,33; 0,66; 1, NC. The group with the highest passability assessment was ROCK group. According to the results measured at low water levels, the passability of rheophilic cyprinids was 24 %. The lowest passability was assessed for Bullhead (14 %). Passability of grayling (59 %) and the Adriatic grayling (51 %) was higher in comparison with rheophilic cyprinids and lower compared to the biggest representative of Salmo family. The highest passability had alien rainbow trout (65 %). We have confirmed that the longitudinal connectivity of Bača river is interrupted along the entire watercourse, which is also shown by the fact that there are 3 obstacles built on average every kilometre.

• Keywords: ecological connectivity, transverse water objects, passability, fish, movements