Survey on performance of vertical slot and nature-like fishways at Angu hydropower station, Southwest China

To restore dam-blocked natural fish migratory passages,a growing number of artificial fishways have been built in water conservancy and hydropower projects in China.The Angu hydropower station involved diverse important fish habitats in the lower reaches of the Daduhe River in Southwest China.Therefore,a vertical slot fishway(VSF)and a nature-like fishway(NLF)were built near the backwater area of the reservoir to connect the upstream and downstream habitats.Hydrodynamic and aquatic ecological surveys were conducted after the completion of the project to estimate the fish passing effect of the two fishways.The results indicated that both fishways were in effective operation and could maintain the desired hydrodynamic conditions and be used by several local fish species.During the survey,149 fish from 15 species and 111 fish from 17 species were captured by the traps in the VSF and NLF,respectively,while 1263 fish from 27 species were found in the downstream area.Some species captured in the VSF were not found in the NLF,and vice versa,which implied the different preferences of fish.Meanwhile,3789 signals including 2099 upward ones and 1690 downward ones were monitored with an ultrasonic fish detector at the inlet of the VSF.These findings revealed the characteristics of fish species observed in and near the fishways and provided valuable insights into the different fish passing capabilities of VSFandNLF.

INFLUENCE OF STRUCTURE ON HYDRAULIC CHARACTERISTICS OF T SHAPE FISHWAY

While dams cut off the migratory route of fish, and affect their growth and breeding, fishways are built to restore the con- nectivity of rivers and facilitate the life cycle of these migratory fish. This paper proposes a new kind of fishway called the ＂T shape fishway＂, and studies it by using both numerical simulations and physical experimental methods with the aim to design a fishway in China for migratory fish with swimming and jumping capability much poorer, such as schizothorax davidi and schizothorax prenanti, as compared with migratory fish in other places of the world, like trout and salmon. It is indicated that the range of velocity in each regular pool of the T shape fishway is from 0.42 m/s to 1.22 m/s when the flow discharge Q is 350 L/s, and there are no large vortex zones found there. This study shows that the T shape fishway can meet the requirements of these migratory fish quite well in terms of velocity and flow patterns in China.

Hydraulics and swimming behavior of schizothorax prenanti in vertical slot fishways

This paper presents a novel experiment for the correlation between the hydraulics and the swimming behavior of Schizothorax prenanti,a rare species of fish in southwest China,in passing a vertical slot fishway.With an acoustic Doppler velocimeter,the velocities of a physical model in the equidimension fishway in the Shaping II power station are measured.The hydraulic parameters include the hydraulic head drop,the velocity patterns and the flow rate,and the swimming behavior includes the burst-coast,the sustained swimming and the migratory path,and they are analyzed under the test conditions.The sustained swimming velocity is in the range from 0.65m/s to 1.09m/s.The estimated hydraulic head drop of each pool is calculated and is in the range from 0.08-0.11 m,which means that 2.6% slope is reasonable.For the same slope,the maximum velocity is further reduced from 1.24 m/s to 1.14 m/s by using an L shape baffle structure.The above findings are used as the basis to evaluate the hydraulic performance of the fishways,where the L shape baffle structure is expected to be effective tor creating a preterencial flow for the fish.For the main stream of the pool,an "Ω" shape flow pattern is more fish-friendly,which can effectively extend the energy dissipation distance and avoid the bursting through a high velocity zone.This paper provides a useful complementary tool for practical designs.

Innovative configuration of vertical slot fishway to enhance fish swimming conditions

A vertical slot fishway(VSF)is among the most effective and commonly used fishway structures to enable fish to pass through artificial barriers such as dams and weirs in the river.Nevertheless,such structures need further improvements in providing better swimming conditions for fish inside the pool and enhancing attraction at the entrance.Therefore,the main objective of this study was to investigate the influence of slope and whether integrating some cylinder structures inside the fishway could enhance further attraction and provide better swimming conditions for fish.This study consists of several numerical simulations,first considering the fishway without cylinder elements while testing three different slopes under two different discharges.Then,the same numerical simulations were conducted,considering cylinder elements of different diameters and arrangements inside the fishway.The numerical model was validated by comparing computed velocities with those measured experimentally from the literature.The results show that the maximum velocity and turbulent kinetic energy(TKE)in the main jet increase as the discharge increases on the same slope.The flow velocity and TKE decrease in the areas inside the pool and between the two baffles.Introducing cylinder elements inside the fishway reduces the principal flow’s maximum velocity.Also,inside the pool,low-velocity regions were expanding.A comparison between the design with a cylinder and the simple VSF indicates that the presence of a cylinder reduced the maximum velocities for the smallest and highest slopes by 6.21%and 9.86%on average,respectively.However,in terms of TKE,cylinders inside the fishway could provide better performance than simple VSF,mainly for low-flow conditions.Finally,this study’s solution-oriented findings provide insights that could help design cost-effective fishways by improving particularly fish attraction to the fishway.

A novel ensemble model for predicting the performance of a novel vertical slot fishway

We investigate the performance of a novel vertical slot fishway by employing finite volume and surrogate models.Multiple linear regression,multiple log equation regression,gene expression programming,and combinations of these models are employed to predict the maximum turbulence,maximum velocity,resting area,and water depth of the middle pool in the fishway.The statistical parameters and error terms,including the coefficient of determination,root mean square error,normalized square error,maximum positive and negative errors,and mean absolute percentage error were employed to evaluate and compare the accuracy of the models.We also conducted a parametric study.The independent variables include the opening between bafles(OBB),the ratio of the length of the large and small baffles,the volume flow rate,and the angle of the large baffle.The results show that the key parameters of the maximum turbulence and velocity are the volume flow rate and OBB.

Evaluation of cone fishways to facilitate passage of small-bodied fish

Fishways are being provided more regularly than ever before and new designs are needed to provide passage for whole fish communities.Despite recent progress,fishways have frequently performed poorly,especially for small-bodied fish(i.e.10-100 mm long),which can form large aggregations below stream barriers.This was the genesis for the development of the cone fishway design,a new style of technical fishway which consists of a series of pre-fabricated cone-shaped concrete baffles installed laterally within a concrete channel.The cone design arose from the need to install rock ramp fishways at remote sites where rock was unavailable and where maintenance would be infrequent.The objective of the present study was to evaluate the suitability of the new cone fishway design to provide passage for small-bodied diadromous species(i.e.<100 mm long).Cone fishways were evaluated at three low head(e.g.<3 m high)case-study sites in tropical and temperate Australia and in total,45 species and 28,556 fish were collected.There was passage of a broad range of the target size-classes of small-bodied fish and individuals as small as nine mm could ascend.However,further work is needed to quantify the proportion of the small-bodied fish population in the river downstream which find and pass through the cone fishways.The most suitable experimental application of the cone fishway is at sites where there is:(i)a narrow(e.g.<0.4 m)headwater range,and(ii)where passage of small-bodied fish is a major ecological priority.Cone fishways provide a useful and novel option to improve passage of small-bodied fish,at appropriate sites,and contribute to a contemporary vision of restoration of whole fish communities.

Monitoring Response of Diadromous Populations to Fish Passage Improvements on a Massachusetts Coastal Stream

One technical fishway and two innovative nature-like fishways were installed at three dams on the Acushnet River in Acushnet, Massachusetts to facilitate migration of river herring and juvenile American eels （elvers）. Pre-construction and post-construction monitoring of river herring and elver populations used census counting and abundance estimation, respectively. Numbers of adult river herring returning to the upstream spawning grounds during the pre-construction phase were very low; elver counts declined during the pre-construction period and served as baseline levels to determine the effectiveness of the new fishways. Post-construction monitoring of river herring and elvers indicated an increasing trend of spawning adult river herring returning to the spawning grounds, with the total count in the fourth year of post-construction representing an increase of 1,140% over baseline, pre-construction conditions. Results also show increased elver recruitment into the river as well as increased proportions of elvers accessing habitat in the upper watershed that was mostly inaccessible prior to fishway installation. The new fishways at the three dams on the river have improved diadromous fish passage, thereby increasing the probability of restoring healthy populations of river herring and American eels to the Acushnet River system.

A Review of Particle Image Velocimetry for Fish Migration

Understanding the flow characteristic in fishways is crucial for efficient fish migration. Flow characteristic measurements can generally provide quantitative information of velocity distributions in such passages;Particle Image Velocimetry (PIV) has become one of the most versatile techniques to disclose flow fields in general and in fishways, in particular. This paper firstly gives an overview of fish migration along with fish ladders and then the application of PIV measurements on the fish migration process. The overview shows that the quantitative and detailed turbulent flow information in fish ladders obtained by PIV is critical for analyzing turbulent properties and validating numerical results.

Vortex identification based on the Liutex method and its effect on fish passage upstream

Fishway research is important for mitigating the fragmentation of river habitats caused by hydraulic projects.The vertical slit fishway is a broadly used fishway type because of its high efficiency and adaptability to water levels.However,the resulting vortex current disrupts the fish passage hence directly affecting fish migration.This study aims to accurately capture the vortex structure in the fishway and analyze the effect of vortex elements(vortex structure,vortex intensity,etc.)on fish.We conducted an analysis of the 3-D current flow field in the fishway through the utilization of an experimental model and the large eddy simulation(LES)method.Moreover,we captured the vortex information in the fishway at different flow rates using the Liutex vortex identification method and investigated the effect of the vortex on fish migration.The results revealed that the structures inside the fishway pool occupy most of the room,however,the areas with higher vortex strength were primarily located in the vortex near the vertical seam and the mainstream,the vortex strength inside the fishway gradually increases with increasing flow,suppressing fish migration.Fish experienced significantly increased resistance when encountering strong vortices.This suggests that the vortex may act as a physical barrier to fish migration.These findings highlight the potential negative effects of vortex on fish movement and reiterate the importance of understanding vortex dynamics for aquatic environmental management.As an effective tool for identifying vortices in fluid flow,the Liutex method demonstrates features of vortex within the fishway,thereby providing important insights into the interaction between fluid dynamics and aquatic organisms.

Editorial: Global fish passage issues

Dams,culverts,and other water diversion/control structures are the most widespread human alteration to riverine habitat globally.While many of these structures often serve critical services(i.e.,source of agricultural and municipal water,power generation,flood protection,and sensitive ecosystem protection),they cause changes to local ecology by impeding animal movement and altering the adjoining habitat and associated ecological processes(Nilsson et al.,2005;Liermann et al.,2007).The disruption of fish movement by barriers has contributed to the decline of both migratory and non-migratory fish populations around the world.

Achieving fish passage outcomes at irrigation infrastructure;a case study from the Lower Mekong Basin

Irrigation infrastructure expansion threatens the diversity of freshwater fish worldwide.Irrigation infrastructure creates migration barriers which can block access to important nursery,feeding and spawning habitat.Lao PDR is a landlocked country situated within the Lower Mekong River Basin where there is a substantial dependency on rice and fish for food,income and livelihoods.The country is experiencing an unprecedented boom in irrigation infrastructure investment,with modernisation programs being implemented in every province.Despite significant investment in infrastructure upgrades,and the potential impact on freshwater fish,little consideration has been given to fish passage solutions.In 2008,we commenced a fish passage program in Lao PDR.The intent of this case study is to outline the pivotal elements of the program of knowledge development and transfer,in the context of river connectivity and fisheries management in Lao PDR.We also highlight challenges in international research in development and lessons learned.