28 research outputs found
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Sensing what fish feel about passage through three different low-head hydropower turbines
Knowing the kinds of physical stress experienced by fish passing through hydropower turbines can help optimise technologies and improve fish passage. This paper assesses the hydraulic conditions experienced through three different low-head turbines, taken using an autonomous sensor: a VLH, Archimedes screw and horizontal Kaplan turbine. A total of 127 Sensor Fish deployments were undertaken across all three turbines, generating 82 valid datasets. Decompression was rare at the VLH and screw turbines and rarely fell more than 10 kPa below atmospheric pressure. In contrast, the Kaplan was capable of generating pressures as low as 55.5 kPa (approximately 45 kPa below atmospheric pressure), over shorter periods of time. Severer ratios of pressure changes could therefore be expected for both surface and depth acclimated fish at the Kaplan when compared to the other turbines. Strike was another possible source of fish injury (detected in 69-100% of deployments), and although strike severity was highest at the Kaplan, strike was more likely to be encountered at the screw and VLH than the Kaplan turbine. Shear only occurred near the blades of the Kaplan and not at severe levels. The results demonstrate that low-head hydropower facilities are not without their risks for downstream migrating fish
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Surface bypass as a means to protect downstream-migrating fish – lack of standardized evaluation criteria complicates evaluation of efficacy
Surface bypasses are downstream migration structures that can help reduce hydropower-induced damage to migrating fish. However, no comprehensive design concept that facilitates good surface bypass performance for a wide range of sites and species is available. This is why even efficiencies at recently built bypass structures vary widely between 0% and up to 97%. We reviewed surface performance studies and existing guidelines for salmonids, eels, and potamodromous species if available to identify crucial design criteria for surface bypasses. Two-tailed Pearson correlation of bypass efficiency and bypass design criteria shows that bypass entrance area (R=0.3300, p=0.0036) as well as proportion of inflow to the bypass (R=0.3741, p=0.0032) are the most influential parameters on bypass efficiency. However, other parameters like guiding structures and trash rack spacing though not statistically significant (Spearman correlation, ordinary t-test) have shown to have an effect on efficiency in some studies. The use of different performance criteria and efficiency definitions for bypass evaluation hampers direct comparison of studies and therefore deduction of design criteria. To enable meta-analyses and improve bypass design considerations we suggest a list of standardized performance parameters for bypasses that should be followed in future bypass performance studies
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Injury and Mortality of Two Mekong River Species to Turbulent Shear Forces
Global hydropower development is one solution proposed to address an increase in energy needs. However, hydropower-related impacts on riverine ecology systems is not well understood. The Mekong River Basin (MRB) is one of the world’s largest waterways and is presently experiencing significant hydropower expansion. It is also one of the most biodiverse rivers; serving as home to many species that are blocked or hindered by the development of dams. One source of injury and mortality for downstream moving fishes is passage through the turbine environment where fishes may be exposed to a number of physical stressors (e.g., shear forces, rapid decompression, blade strike and turbulence). The current study sought to understand the susceptibility of blue gourami (Trichopodus trichopterus) and iridescent shark (Pangasianodon hypophthalmus) to shear forces. Fishes were exposed to an underwater jet with velocities up to 21.3 m/s (equating to strain rates of up to 1,185 s-1). Fish were assessed for behavioral effects, injuries, and mortality. Overall, it was determined that both species were susceptible to shear forces and the effects were more pronounced at higher strain rates. Gouramis were more susceptible than sharks. To minimize impacts on these species, shear forces within turbines should not exceed critical limits
Aquatic Acoustic Metrics Interface Utility for Underwater Sound Monitoring and Analysis
Fishes and marine mammals may suffer a range of potential effects from exposure to intense underwater sound generated by anthropogenic activities such as pile driving, shipping, sonars, and underwater blasting. Several underwater sound recording (USR) devices have been built to acquire samples of the underwater sound generated by anthropogenic activities. Software becomes indispensable for processing and analyzing the audio files recorded by these USRs. In this paper, we provide a detailed description of a new software package, the Aquatic Acoustic Metrics Interface (AAMI), specifically designed for analysis of underwater sound recordings to provide data in metrics that facilitate evaluation of the potential impacts of the sound on aquatic animals. In addition to the basic functions, such as loading and editing audio files recorded by USRs and batch processing of sound files, the software utilizes recording system calibration data to compute important parameters in physical units. The software also facilitates comparison of the noise sound sample metrics with biological measures such as audiograms of the sensitivity of aquatic animals to the sound, integrating various components into a single analytical frame. The features of the AAMI software are discussed, and several case studies are presented to illustrate its functionality