Ecological Connectivity - R&D Projects

BAW and BfG cooperate in Research & Development (R&D) regarding ecological connectivity. To answer questions pertaining to hydraulic and construction issues of fishways BAW and BfG set up projects, cooperate with universities and network with national and international research institutions. The research projects employ physical models and numerical simulation processes to examine hydraulic structures and systems. The BAW also operates a large flume in Karlsruhe to solve particular questions by conducting ethohydraulic tests. Findings of R&D will be extended to and reassessed at designated fishway pilot sites. Results of R&D are integrated into design recommendations and standardisation processes of fishways for the German Federal Waterways and Shipping Administration.

The BfG/BAW research concept sets the frame for the institutions’ joint research activities.

Research project "Special fishway structures"

On large inland waterways it is often necessary to discharge auxiliary water in addition to the operating flow in order to produce an attraction flow which ensures that the fishway can be located. The quantity of auxiliary water needed is often substantial, requiring special structures for which no specific design recommendations are available. The BAW is dealing with this topic in two subprojects, one of which is conducted in co-operation with the Leichtweiß Institute for Hydraulic Engineering and Water Resources at Technische Universität Braunschweig, addressing the issue of providing the auxiliary water as well as calming and homogenisation of flow in the auxiliary water inflow. In a second subproject, design solutions for the entrance pool into which the auxiliary water is injected are developed. Here, research is focusing on the unhindered passage of fish into the fishway, with a particular emphasis on conducting preliminary studies for specific construction elements with scale models before testing these elements in ethohydraulic trials.

Research project "Time-dependent flow processes"

The hydraulics in fish passes is usually evaluated based on time-averaged flow velocities. In turbulent flows in and at fish passes, however, the temporal flow velocity changes and their structure play an important role in how fish sense the flow. In a previous project, a methodology for describing dynamic processes in flow fields has been developed based on PIV measurements in a vertical-slot fish pass. The aim of the present project is to adapt this methodology to further relevant scales. In order to gain a better understanding of the effects of hydraulics on fish behaviour and to verify the previously developed methodology, fish behaviour experiments are performed in the ethohydraulic flume of the BAW.

Research project "ELAM attraction"

Based on previous research a model is being developed to evaluate the attraction of fishways in the tailwater of hydropower plants. The method primarily applied is individual-based modelling using the "Eulerian-Lagrangian-agent method" (ELAM). For the model's development, data from extensive fish observations carried out by BfG by means of acoustic telemetric field investigations in the tailwater of the pilot facility in Eddersheim are used. To simulate the flow field in the tailwater of hydropower plants, the BAW uses three-dimensional numerical models which are developed in OpenFOAM®. The ELAM combines their results with a behavioural model.

Research project "Downstream fish passage over weirs"

Besides upstream fish migration, downstream fish passage also plays a significant role in achieving the objectives of the European Water Framework Directive. While discussions have been focusing on fish protection and downstream migration at hydropower plants for some time now, the issue of downstream passage at weirs has increasingly gained importance. The project aims at developing a numerical model which represents the hydraulic processes occurring in a weir spillway as realistically as possible. Based on this model, the movements of passive floats (used as substitutes for fish) are examined to assess the risks of damages to the fish and better evaluate the related potentially harmful processes occurring during the fish’s descent over weirs. The project is a co-operation between the BAW’s Hydraulic Structures section and the Institute for Hydromechanics (IfH) at Karlsruhe Institute of Technology (KIT).

Research project "Attraction of upstream fishways" (completed)

In a co-operation with the Dieter-Thoma Laboratory and the Obernach Research Institute at the Technical University (TU) of Munich, the BAW conducted a research on the attraction of upstream fishways in the tailwater of hydropower plants. In addition to the development of parameters for the turbine outflow from hydropower plants and the modelling of the outflow in physical and numerical models, the assessment and definition of a good attraction flow to ensure attraction were relevant research topics. The project results provided the basis for dimensioning the attraction flow (recommendation in preparation) and planning the pilot facilities. The project data were also used as material for a doctoral thesis prepared at the TU Munich.

Research project "Passability of vertical slot fishways" (completed)

In a co-operation with the Institute for Water and River Basin Management at Karlsruhe Institute of Technology, researchers looked into the hydraulics of vertical slot passes for upstream fish migration. An important part of the research co-operation involved describing the temporal fluctuations of the flow fields in the fishway and whether they can be anticipated by the animals. This subproject was concluded with a doctoral thesis. Another subproject investigated how the time-averaged flow fields manifest themselves in different flow patterns in the fishway pools. The flow patterns have an effect on the pools’ energy balance and the degree of passability. Additional tests were made to analyse the energy dissipation in the pools, e.g. regarding flow velocities and roughness values, and to develop specific approaches for determining discharge. The data collected were also used for developing physical and numerical modelling.

Research project "ELAM-de" (completed)

An important criterion for the assessment of a fishway is its efficiency, which is, however, difficult and time-consuming to determine in the field or laboratory. A numerical model for simulating fish behaviour on spatial and temporal scales of decimetres and seconds, respectively, can support planning decisions and contribute to scientific understanding of the performance of competing fishway designs. Based on the "Eulerian-Lagrangian-agent method" (ELAM), a new individual-based model ("ELAM-de") was developed. The model was fed with three-dimensional flow data calculated with OpenFOAM® on arbitrary polyhedral meshes. It was designed, calibrated and validated based on behavioural patterns derived from the movements of live brown trout. The project was concluded with a doctoral thesis (in co-operation with the Bundeswehr University Munich).

Link to final report

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