Author(s): G. Fiedler.; L. Mahl; R. B. Weichert

Linked Author(s):

Keywords: Fish; Upstream migration; Physical modelling; Mixing; Auxiliary water system; Flow expansion; Hydraulic structures

Abstract: The German Waterways and Shipping Administration (WSV) is responsible for the restoration of upstream migration of fish at the federal waterways. For that purpose, a large number of fish passages have to be built in the near future. As federal waterways are usually characterised by large channel widths, it is an important aspect that fish find the entrance of a fishway. The sensory capabilities of fish are manifold. However, it is generally accepted that fish mainly orientate on the flow during their upstream migration. In this respect, the attraction flow of a fishway in the tailwater of a dam becomes relevant as its purpose is to compete with the flow of a hydro power plant or a weir discharge. Following this, the basic flow of a fishway is not sufficient at larger dams, so that auxiliary flow has to be added through screens in the side walls of the fishway entrance pool. As the added discharge may exceed the basic discharge of the fishway significantly, it is important to design the auxiliary water system in a way that the swimming behaviour of fish is not influenced negatively. Generally accepted design recommendations for auxiliary water systems in fishways are virtually non-existent. At the Federal Waterways Engineering and Research Institute (BAW), physical and numerical model studies have been carried out that focus on the hydraulics of auxiliary water systems. The requirements given by fish biologists define a flow with low velocities and turbulence intensities. As the auxiliary water is usually taken from the head water of a dam, the energy height of the flow adds up to some few metres. Consequently, the main challenge is to work up technical solutions under difficult conditions with a severe lack of space. In a first step, technical solutions were developed for pilot sites that are currently in the planning stage. Afterwards the study aims to extend these technical solutions to a broad range of boundary conditions.

DOI: https://doi.org/10.15142/T3735F

Year: 2018