Mechanical injury is among the most significant and least understood injury mechanisms for fish during downstream dam passage. Mechanical injuries to fish are caused by their collision with hydraulic structures, such as fixed guides, stay vanes, wicket gates, flow-straightening walls in the draft tube, and moving turbine runner blades. Information on mechanical strike is necessary for establishing biological criteria for operation and design of turbine and non-turbine structures. Hatchery-reared juvenile fall Chinook salmon (Oncorhynchus tshawytscha) that were 110-140 mm long were introduced through a submerged, 6.35 cm diameter water jet at velocities ranging from 9.1 to 18.3 m/s and encountered a fixed hydraulic structure. The structures included a baffle block, a deflector, and a model of the leading edge of a turbine blade. All the exposures were captured by two high-speed cameras. Three-dimensional trajectories were obtained by performing motion analysis on the videos. Velocity and acceleration were then computed by numerical differentiation of the trajectories. For all three configurations, fish exited the nozzle and impacted the structures at roughly the same velocities. Velocities tested were 9.1, 12.2, 15.2, and 18.3 m/s for the baffle block and 9.1, 12.2, and 15.2 m/s for the deflector and blade. Injury levels for each group increased with increasing nozzle velocity. Minor injury first occurred at 9.1 m/s for both the blade profile and baffle block tests. Major injuries were near 40% for both the baffle block and blade profile test at velocities of 15.2 m/s. Direct and delayed mortality were near 50% for all speeds using the blade profile and direct mortality increased from 10% to 50% with the baffle block. Injuries were far less common when using the deflector, with major injuries of similar to 5% at a velocity of 15.2 m/s. The findings of this study can reveal ways these structures can impair juvenile salmonids' ability to safely pass hydroelectric facilities.

As hydropower continues to play an important role in renewable energy production, there is a continuing need to mitigate or eliminate the negative effects of hydropower on fish populations. This study examined a novel hydropower turbine (Restoration Hydro Turbine) designed to maximize safe passage with survival rates exceeding 99 %. Tests using adult hatchery-reared rainbow trout (Oncorhynchus mykiss) were performed over two trial periods, one in 2020 and the other in 2022, at the Monroe Drop Facility in Jefferson County, Oregon. Of the 166 treatment and 141 control fish tested over the two years (fork length 200-530 mm, mass 305.0-1225.5 g), no immediate mortalities or major injuries were observed. The results of this study indicate a very high likelihood of immediate survival (100 % in 2020, 98.6 % in 2022) for rainbow trout in the size range examined when passing through the turbine. The absence of major injuries and mortalities attributable to turbine passage demonstrates the potential of novel turbine designs to minimize fish injury during hydropower generation.

American shad (Alosa sapidissima) are an anadromous fish species native to North America that have an extensive range, but their populations are declining. Acoustic telemetry can play a vital role in better understanding the behavior and survival of this sensitive species, but successfully handling and tagging juvenile American shad can be challenging. We conducted several experiments to determine the best methods for collecting, transporting, holding, and tagging juvenile shad. Minimizing out-of-water handling and the use of a saltwater treatment during collection increased 24 h survival from 78 to 99% after transport. Saltwater was also fundamental in keeping tagged shad alive overnight. Shad as small as 50 mm, were implanted with a dummy acoustic transmitter using a pectoral incision method with no suture. In a 60 d holding evaluation, the tagged fish survived at a rate comparable to their non-tagged counterparts (81.5% for tagged, 70% for untagged). Tagged and untagged shad also had similar survival when exposed to a tank of predators. The results are important for improving conservation efforts for small, sensitive species of fish, like American shad.

The use of telemetry techniques to better understand the behavior and survival of juvenile American shad (Alosa sapidissima), as they migrate through hydropower systems, has been challenging because shad are widely known to be particularly sensitive to handling. The goal of this study was to develop a tagging protocol using a new, acoustic micro transmitter that minimizes the detrimental effects of the tagging process and maximizes post-tagging survival of juvenile American shad. Limiting out-of-water handling and the use of brackish saltwater (7.5 parts per thousand) before and after tagging improved survival for shad tagged using a simple pectoral implantation method. This protocol provides a detailed, step-by-step procedure for tagging juvenile shad with acoustic transmitters. Fish tagged using this procedure and held in the laboratory for 60 days had an 81.5% survival rate, compared to 70% for their untagged counterparts. The successful tagging and handling practices developed in this study could be applied to field telemetry studies of juvenile shad and other sensitive species.

The tensile mechanical properties of metals manufactured by laser powder bed fusion (L-PBF) are known to vary systematically between builds, posing challenges for the qualification and adoption of L-PBF. In this work, we systematically investigated two mechanisms that have previously been used to explain systematic differences in mechanical behavior of notionally identical L-PBF samples between builds (so called "inter-build variation"): porosity and laser parameter drift. Over 250 tension coupons, each with unique laser processing parameters, were built in 316 L stainless steel across three L-PBF builds, screened using high-resolution X-ray Computed Tomography to quantify internal porosity, and then mechanically tested. Notionally identical samples from one build showed statistically significant differences in porosity (0.045%, vs. 0.001% for the "best" build), ultimate tensile strength (614 vs. 588 MPa), and elongation (0.267 vs. 0.321 strain to failure), revealing meaningful levels of inter-build variation. Statistical and machine-learning guided interrogation of the relationships between laser processing conditions, porosity and mechanical response showed that the both laser parameter drift and sys-tematic differences in porosity can both adequately explain observations of inter-build variation, but their effects are nonlinear and are most relevant in different regimes of build quality. In the present case, laser parameter drift within high-density samples can result in material with improved strength and reduced ductility due to micro -structural refinement; on the other hand, porosity above-0.1% that is caused by process drift or other means contributes to rapid embrittlement, as in (Boyce et al., 2017).

The metal additive manufacturing (AM) process uses high-power lasers to rapidly melt and solidify metal powder into complex 3-D shapes, but unfortunately the rapid solidification process often results in stochastic defect formation and nonequilibrium microstructures. To fully understand the AM process and ensure a high-quality, defect-free manufacturing process, novel high-speed sensing methods that can capture key physical phenomena associated with the AM process at high resolution are needed. A team at the Johns Hopkins University Applied Physics Laboratory (APL) is developing novel spectrometry techniques capable of measurement speed exceeding 50 kHz along the laser path to aid in understanding how materials are formed under different laser inputs. The team is also developing machine learning tools to interpret these signals, thus revealing features and trends that are not apparent to human analysts in the sensor data or physi-cal post mortem inspection results of the printed components.

A framework for additive manufacturingAdditive manufacturing aluminum alloyAluminum alloys selection was developed to determine the preferred composition and process parametersProcess parameters from which to fabricate topology-optimized optical instrument housings and light-weighted freeform mirrors for the Compact Hyperspectral Air Pollution Sensor (CHAPS). In recent years, a number of high-strength laser powder bed fusionLaser-powder bed fusion aluminum alloysAluminum alloys have become commercially available, which are attractive for aerospace applications due to their high specific strength. Three aluminum alloysAluminum alloys were selected for a three-Round experimental comparison. Each Round used a down-selected subset of alloys and parameter sets (candidates) from the previous Round. Round 1 screened a wide range of laserLaser parameter sets for those that produced the highest density and tensile yield strength. Round 2 evaluated build quality using test geometries representative of CHAPS and assessed compatibility with post-processingProcessing, including optically black coatingCoating for the optical housings and nickelNickelphosphorus plating for the mirrors. Round 3 characterized anisotropyAnisotropy in tensile and thermal properties. A rating system was developed which involved assigning priority weighting for CHAPS-specific criteria and binning test results into scoring categories to give a comparison score for each candidate which was used in the down-selection between Rounds. The framework selection process enabled a comparison of the relative strengths and weaknesses of each candidate and resulted in the selection of Scalmalloy as the preferred alloy for CHAPS. The selected candidate was used to develop designDesign allowables for the topology optimization of CHAPS prototype housings, which were then fabricated.

ObjectiveStudy the effects of downstream passage through a novel turbine designed for fish safety, the Restoration Hydro Turbine (RHT), on American Eels Anguilla rostrata in a recirculating turbine test facility. MethodsA 55-cm-diameter RHT was operated under 10 m of hydraulic head and 667 revolutions/min. In total, 131 eels were passed through the turbine and 43 eels were used as experimental controls (length = 33.9-65.5 cm). High-speed video of passage through the runner region was captured for 89% of turbine-passed eels, and injury and behavioral effects were recorded immediately before and after passage, as well as after a 48-h holding period. A subset of 37 eels was additionally examined with X-ray imaging for internal injuries. ResultThe 48-h survival rate for both treatment and control groups was 100%, with no major internal or external injuries present after the holding period. ConclusionThis is a substantial improvement over eel survival rates through conventional Kaplan and Francis turbines, which may range from 40% to 95%, and suggests that hydropower turbines designed for safe downstream fish passage could be implemented without major impacts to eels.

A diversified energy portfolio may include marine energy in the form of current energy converters (CECs) such as tidal or in-river turbines. New technology development in the research stage typically requires monitoring for environmental effects. A significant environmental effect of concern for CECs is the risk of moving parts (e.g., turbine blades) colliding with animals such as fishes. CECs are installed in energetic locations in which it is difficult to operate sensors to fulfill monitoring requirements for informing collision risk. Collecting data (i.e., about blade strikes or near-misses) that inform interactions of fishes with CECs is usually attempted using active acoustic sensors or video cameras (VCs). Limitations of low-light conditions or water turbidity that preclude effective use of VCs are overcome by using high-resolution multibeam echosounders (or acoustic cameras (ACs)). We used an AC at two sites to test its ability to detect artificial and real fish targets and determine if strike, near-miss, and near-field behavior could be observed. Interactions with fish and artificial targets with turbines have been documented but strike confirmation with an AC is novel. The first site was in a tidal estuary with a 25 kW turbine and water clarity sufficient to allow VC data to be collected concurrently with AC data showing turbine blade strike on tethered artificial fish targets. The second site was a turbid, debris-laden river with a 5 kW turbine where only AC data were collected due to high water turbidity. Data collection at the second site coincided with downstream Pacific salmon (Oncorhynchus spp.) smolt migration. Physical fish capture downstream of the turbine was performed with an incline plane trap (IPT) to provide context for the AC observations, by comparing fish catches. Discrimination between debris and fishes in the AC data was not possible, because active movement of fishes was not discernable. Nineteen fishes were released upstream of the turbine to provide known times of possible fish/turbine interactions, but detection was difficult to confirm in the AC data. ACs have been used extensively in past studies to count large migratory fish such as Pacific salmon, but their application for small fish targets has been limited. The results from these two field campaigns demonstrate the ability of ACs to detect targets in turbid water and observe blade strikes, as well as their limitations such as the difficulty of distinguishing small fishes from debris in a high-energy turbid river. Recommendations are presented for future applications associated with CEC device testing.

This report documents an investigation into the performance of a novel fish-protection screen intended to prevent small aquatic and marine organisms from entering water intakes in free-flowing water bodies. The proposed prototype screen resembles conventional, slotted fish-protection screens with parallel wires or bars; however, the prototype bars are shaped to mimic the filter elements in the mouths of filter-feeding fishes such as the devil ray (Mobula tarapacana). Millions of years of evolution have perfected these structures to provide energetically efficient and clog-resistant filtering of zooplankton from seawater. The intent of the prototype is to exploit these mechanisms for the protection of similarly sized, or larger, organisms in settings where the freely flowing current is approximately parallel with the screen face (i.e., sweeping flow) and perpendicular to the screen bars.

In context of the universal presence of defects in additively manufactured (AM) metals, efficient computational tools are required to rapidly screen AM microstructures for mechanical integrity. To this end, a deep learning approach is used to predict the elastic stress fields in images of defect-containing metal microstructures. A large dataset consisting of the stress response of 100,000 random microstructure images is generated using highresolution Fast Fourier Transform-based finite element (FFT-FE) calculations, which is then used to train a modified U-Net style convolutional neural network (CNN) model. The trained U-Net model more accurately predicted the stress response compared to alternative CNN architectures, exceeded the accuracy of lowresolution FFT-FE calculations, and was generalizable to microstructures with complex defect geometries. The model was applied to images of real AM microstructures with severe lack of fusion defects, and predicted an increase of maximum stress as a function of pore fraction, and higher stress compared to comparable microstructures with circular holes. Together, the proposed CNN offers an efficient and accurate way to predict the structural response of defect-containing AM microstructures.

Adult American eels (Anguilla rostrata) are vulnerable to hydropower turbine mortality during outmigration from growth habitat in inland waters to the ocean where they spawn. Imaging sonar is a reliable and proven technology for monitoring of fish passage and migration; however, there is no efficient automated method for eel detection. We designed a deep learning model for automated detection of adult American eels from sonar data. The method employs convolution neural network (CNN) to distinguish between 14 images of eels and non-eel objects. Prior to image classification with CNN, background subtraction and wavelet denoising were applied to enhance sonar images. The CNN model was first trained and tested on data obtained from a laboratory experiment, which yielded overall accuracies of >98% for image-based classification. Then, the model was trained and tested on field data that were obtained near the Iroquois Dam located on the St. Lawrence River; the accuracy achieved was commensurate with that of human experts.

American eel (Anguilla rostrata) populations have declined within their native range along the eastern coast of North America due to factors such as commercial fishing, habitat alteration, and dams. American eel are catadromous fish species, and high mortality rates (>40%) have been observed for freshwater life-stage adult eel passing downstream through hydropower turbines. Lacerations and sectioning of fish have been observed downstream of turbines and these injuries are commonly associated with direct contact with the turbine runner, whether through blade strike or pinching and grinding. Exposure to fluid shear may also be a source of injury, however, little is known about American eel susceptibility to this physical stressor. Eels are considerably flexible when compared to other fish species and lack other morphological characteristics that would make them susceptible to fluid shear, such as protruding eyes, large scales, and large operculum. European eel, which have previously been tested for susceptibility to fluid shear, were found to be resilient. To determine if American eel are also resilient to fluid shear, forty American eel were exposed to a water jet, simulating severe fluid shear (strain rate > 800 s−1) that fish may experience when passing downstream through turbines. No immediate or delayed (48 h) signs of injury were observed after exposure to severe fluid shear. Based on this study, and a previous study conducted on American eel susceptibility to barotrauma, the source of injury and mortality of American eel passing through turbines is likely attributed to blade strike or pinching and grinding.

This study, funded by the U.S. Army Corps of Engineers (USACE), was conducted by the Pacific Northwest National Laboratory to evaluate the efficacy of operating one Top Spill Weir (TSW) at McNary Dam outside the normal TSW operation dates for juvenile salmon passage. Of interest is whether the TSW is an effective downstream passage route for adult steelhead overshoots. Overshoots are fish which, having passed upstream at McNary Dam, must pass downstream to return to their natal stream to spawn. This report covers Fall (2019) and Spring (2020) study periods. The study design arranged the available 24 hours of TSW spill per week into weekly blocks with sub-blocks differentiated into day and night operations with TSW discharge periods of 4- and 8-hours duration. Hydroacoustic techniques were used to sample adult fish passage at the TSW and at turbine units 1 and 10. The experimental design contrasted TSW spill periods of differing duration and at different times of the day. The small number of fish detected passing the TSW, and the smaller number of fish detected passing the turbine units, were best suited to an ad hoc, exploratory approach to evaluating the effect of TSW spill. It is worthwhile to note that the operations data obtained for the fall study period had a greater than expected number of gaps and apparent anomalies that we believe were a result of how the data were aggregated. These problems are not particularly problematic for the present study, because the available data still provide a good indication of whether the TSW was operating at each point in time. TSW flows in both fall and spring data sets were able to be cleaned up using the established relationship between forebay elevation and TSW discharge rate. Additional cleanup of operations data would be needed, however, if more quantitative evaluation of dam-wide flow and passage relationships were needed. This study contrasted TSW spill periods of differing duration and at different times of the day. The small number of fish detected passing the TSW, and the smaller number of fish detected passing the turbine units were best suited to an ad hoc, exploratory approach to evaluating the effect of TSW spill. Spring adult steelhead passage numbers estimated using hydroacoustics were notably lower than during the fall study period, and that was consistent with our analysis of PIT tagged fish likely to be in the vicinity during each study period. Detections of fish in BlueView sampling areas upstream of the TSW and powerhouse were not correlated with detections of fish passing hydroacoustic sampling areas, which suggests that fish approaching the face of the dam can move around the forebay before passing. Other fish detected in the forebay in large numbers, such as shad, were able to be filtered out of steelhead passage counts and did not appear to be influencing hydroacoustic passage rate estimates. A pulse of passage at the initial TSW opening was weakly evident, but trends across 4- and 8-hour operational periods did not show a distinct decline in passage over time as TSW operation continued. Our findings do not indicate a reason to choose one 8-hour period over two 4-hour periods, or vice versa. This suggests that the duration of spill periods can be chosen based on operational or other considerations. Passage rates were consistently higher during the daytime TSW discharge periods, relative to nighttime TSW discharge periods. The experimental design of the current study used start times near dawn for day periods and near dusk for night periods.

Water diversions are very common in agricultural landscapes, providing water to irrigate a diverse range of crops. Larval Pacific Lamprey Entosphenus tridentatus are vulnerable to entrainment during the irrigation withdrawals and can be exposed to desiccation or predation during dewatering at the end of the irrigation season. A customized portable deepwater electrofishing system was deployed to determine larval lamprey densities at two large scaled irrigation diversion canals located on the Yakima River in eastern Washington. The system components can be easily transported to a remote survey site due the number of components and minimal total weight. The surveys were conducted in the fall during the dewatering period in 2015 and 2017, and the densities for larval lampreys ranged from 0.8 to 8.8 fish/m(2) at the Sunnyside Canal and 4.2 fish/m(2) at the Wapato Canal (2015 only). Our results indicate that the use of the deepwater electroshocking system was effective at determining larval lamprey presence and densities in hard-to-sample irrigation canals.

Throughout many areas of their native range, American shad (Alosa sapidissima) and other Alosine populations are in decline. Though several conditions have influenced these declines, hydropower facilities have had significant negative effects on American shad populations. Hydropower facilities expose ocean-migrating American shad to physical stressors during passage through hydropower facilities, including strike, rapid decompression, and fluid shear. In this laboratory-based study, juvenile American shad were exposed separately to rapid decompression and fluid shear to determine their susceptibility to these stressors and develop dose–response models. These dose–response relationships can help guide the development and/or operation of hydropower turbines and facilities to reduce the negative effects to American shad. Relative to other species, juvenile American shad have a high susceptibility to both rapid decompression and fluid shear. Reducing or preventing exposure to these stressors at hydropower facilities may be a potential method to assist in the effort to restore American shad populations.

The Chapter 10 Supplementary Material provides information on instrument classes used for monitoring marine renewable energy devices such as passive acoustics, active acoustics, and video cameras. It also describes the applications and challenges of video cameras, and provides a technical glossary related to monitoring terminologies.

The greatest potential risk from turbine operation continues to be perceived by regulators and other stakeholders to be that of marine animals colliding with turbine blades. These potential interactions are the most difficult to observe using common oceanographic instruments and must be undertaken in parts of the ocean where fast moving water and high waves make studies challenging. However, our collective understanding of the effects of marine renewable energy (MRE) devices on marine animals and their habitats has improved since the publication of the 2016 State of the Science report. https://tethys.pnnl.gov/publications/state-of-the-science-2020-chapter-10-environmental-monitoring

There are two strategies to lower overall project costs to an extent that will make many potential sustainable hydropower sites economically viable: (1) design standardized/modular components; (2) use advanced tools to reduce environmental evaluation costs. In this study an autonomous sensor device (Sensor Fish) was used to study a Francis turbine retrofitted with a modular guide vane. The median nadir pressures measured were 74.7, 66.6, and 56.6 kPaA for 90-, 190-, and 380-kW operating conditions respectively. These nadir pressures were compared to other Francis turbines studied using Sensor Fish and were found to be within the same range. The proportion of Sensor Fish releases with severe acceleration events (acceleration >= 95G) was also investigated. The proportion ranged from 73 to 80% (runner region), 50 to 64% (guide vane region), and 9 to 28% (draft tube region), which was within the range of the other turbines used for comparison. The Sensor Fish testing that was conducted at Hurley Dam demonstrates that the modular guide vane that was retrofitted to the existing Francis turbine is potentially a suitable replacement that can provide biological performance similar to the guide vane used with other existing Francis turbines, but with the benefit of reduced fabrication costs.