Abstract:
In Switzerland hydropower production contributes roughly 60% to the electricity supply. However for the protection of fishes almost no downstream migration facilities yet exist. Until 2030 all hydropower facilities have to provide a safe downstream migration corridor for fishes. In Europe some technological solutions exist to enable downstream migration at small hydropower plants, but no analogous solutions exist for larger hydropower facilities. Guidance efficiency of five fish species (barbel, spirling, brown trout, eel and grayling) was tested in a laboratory flume with modified bar racks and louvers angled at 30 and 15 degree to the approaching flow (0.3-0.9 m/s). The bar spacings were 5 and 11 cm. The test fishes were collected from wild river populations using electrofishing techniques. A total of 34 different configurations were evaluated. For selected experiments we additionally used a bottom overlay in order to increase the guiding efficiency. All the experiments were documented with video recordings. A detailed analysis of the flow is presented by the companion paper by Albayrak et al. (2015). The main angle of the guiding array (15 or 30 degree) did not have a significant effect on the guidance efficiency. Apart from the spirlin the increase in flow velocity did not affect the successful bypass passage. The guidance efficiency was • higher for bar racks and louvers with clear spacings of 5 cm, compared to 11 cm • higher for bar racks than for louvers (tested with barbel and spirlin) • considerably higher with a bottom overlay, notably for grayling. Our studies showed that angled bar racks have a striking potential for diverting European fish species away from turbine intakes. However additional lab and field studies (at a pilot hydropower plant) are needed and more fish species have to be tested