Abstract
The spatial distribution of fish upstream of a vertical trash rack was investigated at the hydropower plant Kirchbichl in the alpine River Inn (Tyrol, Austria). The objective of the research project “FIDET” was to establish a non-invasive methodology to study fish presence and flow characteristics at large hydro power sites. A new monitoring approach was developed combining hydroacoustic observations of fish locations with multivariate hydrodynamic data. This was accomplished by utilizing complementary observations from multiple underwater sensor technologies: First, an array of echosounders were deployed at a fixed cross-section upstream of the trash rack for long-term monitoring. Afterwards, detailed underwater surveys with “acoustic cameras” (DIDSON and ARIS) revealed that the spatial distributions of fish in front of the trash rack were highly heterogeneous. The spatial distribution of the flow field was assessed via the time-averaged velocity fields from acoustic Doppler current profiler (ADCP). Finally, a custom pressure-based flow turbulence probe was developed, providing spatial estimates of flow turbulence immediately upstream of the trash rack. The significant contribution of this work is to provide a multi-modal monitoring approach incorporating both fish position data and hydrodynamic information. This forms the starting point for a future objective, namely to create an automated, sonar-based detection and control systems to assist and monitor fish protection operations in near real-time.
Highlights
European research on downstream migration of fish began some 30 years ago [1,2,3,4], and has increased substantially in the last decade, especially in Germany [5,6,7]
The spatial distribution of fish upstream of a vertical trash rack was investigated at the hydropower plant Kirchbichl in the alpine River Inn (Tyrol, Austria)
A new monitoring approach was developed combining hydroacoustic observations of fish locations with multivariate hydrodynamic data. This was accomplished by utilizing complementary observations from multiple underwater sensor technologies: First, an array of echosounders were deployed at a fixed cross-section upstream of the trash rack for long-term monitoring
Summary
European research on downstream migration of fish began some 30 years ago [1,2,3,4], and has increased substantially in the last decade, especially in Germany [5,6,7]. The majority of studies are focused on diadromous fish, such as Atlantic salmon [8,9] and European eel [8,10,11]. The ongoing discussion on fish protection and downstream migration focuses on three key aspects: (1) The catchment area and its representative target species; for example, the Danube versus the Rhine, where Atlantic salmon and European eel naturally occur only in the Rhine catchment. (3) Differences in the hydropower plant design, especially the turbine size and type. Based on these three aspects, it has been established that a case-by-case examination is necessary to determine the balance between ecological need and economic utility at each hydropower facility [14,15,16]
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