High Water Velocity Research Articles

Effects of exercise training on growth and physiology of large-mouth bass (Micropterus salmoides) reared in a recirculating aquaculture system

Large-mouth bass originally lived in rivers and lakes and now is often raised in recirculating aquaculture systems (RAS). However, the shortcoming of RAS is that there is very limited space for swimming fish in a high-density culture environment, thus leading to a lack of exercise. To investigate the effects of exercise training on growth performance, digestive enzymes, stress, and antioxidant capacity of large-mouth bass in a RAS, three training water flow velocities with three replicates were used in the present study: low water velocity: 0.5 body length per second (bl/s) (LV); medium water velocity: 1 bl/s (MV); and high water velocity: 1.5 bl/s (HV). 270 large-mouth bass (average initial body weight 47.51 ± 1.44 g, initial body length 12.71 ± 0.06 cm) were randomly divided into nine tanks (30 fish per tank). After 27 days experiment, the results showed that the growth performance of large-mouth bass, including feed intake, weight gain rate, and specific growth rate, in the HV group was significantly higher compared to the other groups. On the physiological level, the lipase and amylase activities were significantly increased in the HV group compared to the other groups. For the stress response parameters, the cortisol, glucose and lactate concentrations in the HV group were significantly increased, which may indicate higher stress in the HV group. Regarding the antioxidant enzyme activities, the activities of catalase (CAT) and glutathione peroxidase (GSH-PX) in the LV group were significantly higher than those in the HV group, which indicated that fish suffered higher oxidative stress in the LV group. Regarding the immune-related parameters, LZM and ACP activities had no significant differences among the groups, while AKP activities in the MV and HV groups were significantly higher than that in the LV group. Overall, the results demonstrated that exercise training had significant effects on the growth, digestion, stress, and immune response of large-mouth bass. It is suggested that exercise training with 1.5 bl/s can enhance fish growth, however, it also presents a potential risk of inducing stress in fish. Therefore, in rearing large-mouth bass in RAS, the setting of water flow velocity should not only focus on the growth of large-mouth bass but also consider its welfare.

Assessment of habitat and hydrological parameters of the lotic and lentic wetlands of the Sonitpur district, Assam, India

This paper represents the riparian zone and water parameters in twelve selected sampling sites of both lotic and lentic wetlands of Sonitpur district. The study has been carried out from January 2021 to February 2023. Data were collected representing all the four seasons of the year. Physical Characteristics viz; soil colour, soil moisture, soil texture, vegetation coverage, canopy coverage and litter depth were assessed during the survey period. Vegetation and canopy coverage of the riparian zone adjacent to the lotic wetlands were found to be the highest. Litter depth (3.1cm) was found to be recorded at a single sampling site S4 . Water quality assessment recorded that Water temperature was found to be one of the major factors having the most intense direct and indirect effect on the riverine system ranged from 4.85±0.02 to 27.60±0.10 in the lotic wetlands and between 11.15±0.02 to 27.44±0.05 in the lentic wetlands. The overall pH value ranged from 6.09±0.05 to 7.24±0.32 in the lotic wetlands and between 6.44±0.02 to 7.52±0.08 in the lentic wetlands which is a convenient zone. DO values ranged from 6.01±0.32 to 7.37±0.22 in the lotic wetlands and between 6.39±0.30 to 7.63±0.30 in the lentic wetlands. Maximum DO value was recorded in the monsoon period. Water velocity was observed to vary from 0.20±0.03 to 1.30±0.28 in the lotic wetlands. Highest water velocity was recorded during the monsoon period and lowest in the winter period.

Unveiling the Potential: Selecting Optimal Materials for Physical Pools in a Pavement-Runoff-Integrated Treatment System

Pavement runoff contains complex pollutants that can lead to environmental pollution and health risks. A pavement-runoff-integrated treatment system has been recognized as an effective way to deal with pavement runoff pollution. However, there is little support for selecting appropriate materials for physical pools due to a lack of understanding of the selective filtration and physical adsorption characteristics. In this study, gravel and activated carbon were chosen as the substrate materials for physical filtration and adsorption pools, and their corresponding purification characteristics were investigated using an indoor scaled down model. The results showed that the removal rate of all pollutants was related to the size of the gravel used. This was mainly due to the increased gravel particle size and voids, which resulted in a higher water velocity, shorter hydraulic retention time, and inadequate filtration. Compared with coconut shell granular activated carbon (GAC) and coal column activated carbon (EAC), analytically pure granular activated carbon (ARAC) showed a better removal rate for petroleum and heavy metals. This is mainly because ARAC has a larger specific surface area, higher pore volume, and wider pore size distribution, resulting in a remarkable adsorption capacity for pollutants. Overall, the combination of 0.3 mm gravel and ARAC was found to be the most suitable for use as filtration and adsorption materials for physical pools. These findings offer a gravel- and ARAC-based pavement-runoff-integrated treatment system, which has excellent potential to enhance the removal of pollutants from pavement runoff.

Investigation on the heat transfer performance of a novel composite energy geo-structure with energy piles and boreholes

Ground source heat pumps (GSHPs) utilize geothermal energy for space heating/cooling with high energy efficiency and low environmental impact, making them a promising option for achieving carbon neutrality. Energy geo-structures, such as energy piles and boreholes, are essential components of the GSHP systems. However, the total heat transfer capacity of energy piles is limited by the number of building pile foundations, while boreholes require significant land occupation and drilling costs. To overcome the limitations of these two single-type energy geo-structures, a novel composite energy geo-structure consisting of energy piles and vertical boreholes is proposed. The minimum energy geo-structure group comprises two boreholes and two energy piles. A sandbox prototype of the composite energy geo-structure is established for experimental measurement and model validation. Additionally, a numerical model of the composite energy geo-structure is developed in COMSOL Multiphysics to investigate heat transfer performance under different influencing factors. Simulations indicate that the composite energy geo-structure exhibits higher heat transfer capacity, deeper heat injection depth, and a larger heat-affected zone in the soil. The central soil temperature of the composite energy geo-structure at a depth of 20 m is 0.8 °C higher than that of a single-type energy pile after one month of heat injection. Additionally, total heat transfer of the energy geo-structure can be increased from 4,110 W to 6,860 W, representing a 67% enhancement. Parametric studies show that heat transfer rate of the energy geo-structure is 26.78–77.71 W/m under different working conditions, soil types, and energy pile spacings. High inlet water temperature and velocity, high thermal conductivity soil, and large pile spacing are beneficial for improving the heat transfer rate of the composite energy geo-structure. Among them, soil type and energy pile spacing have more significant effects on long-term performance. The proposed composite energy geo-structure demonstrates better performance than conventional single-type energy piles or boreholes, contributing to its rational design and performance optimization, effectively promoting broader applications of GSHP systems.

2D and 3D Numerical Simulation of Dam-Break Flooding: A Case Study of the Tuzluca Dam, Turkey

Unlike river floods, floods caused by dam breaks occur much more abruptly and at higher water velocities. The failure of a dam due to any reason can pose a significant threat to settlements in the downstream area due to the high volume of water in its reservoir. In this case study, 2D and 3D numerical failure simulations of Tuzluca Dam, to be built in the Igdir province of Turkey, was performed using the Flow3D Hydro software. The Shallow Water and Reynolds-Averaged Navier-Stokes (RANS) equations were used to simulate flood propagation. In the numerical models, RNG k-ε was chosen as the turbulence model. In the analyses carried out under different scenarios, it was observed that in both methods (2D and 3D), significant flood depths would occur in two downstream village settlements. Within the scope of the study, the mortality rates in different dam-break scenarios of the Tuzluca Dam were also investigated. It has been observed that the dam failure time and breach geometry have a significant impact on the flood propagation and the loss of life in settlements. Additionally, a dam-break experiment in literature dam-break experiment was numerically solved using the Flow3D Hydro software to validate the numerical model, and a satisfactory harmony was observed between the experimental results and the numerical models. Although the 3D analysis provided a more accurate representation of the experimental results, it took approximately 20 times longer to complete the dam failure simulation in the case study compared to the 2D model. As a result, it has been determined that for comprehensive studies such as those of dam failures, 2D analyses may be more practical, while for smaller-scale scenarios or situations requiring greater precision, 3D modelling is appropriate.

Experimental study of the effect of mechanical vibration and water velocity on bubble management in PEM electrolysis cell

The anode of a proton exchange membrane electrolysis cell (PEMEC) has a complex two-phase flow. Excessive gas concentrations tend to build up on the catalyst layer (CL) surface and inside the porous transport layers (PTLs), inhibiting electrolytic reactions from occurring. Therefore, efficient bubble management methods are required. In this paper, the principle of actions and the effect of mechanical vibration and water velocity as methods of bubble management are investigated. PEMEC bubble kinetic and two-phase flow performance were investigated using high-speed optical imaging at different amplitudes, frequencies and water velocities, and the results were correlated with electrochemical performance. The results show that the vertical sinusoidal vibration can cause cyclic compression of the PTL by the ribs, which promote the discharge of the blocked gas into the flow channel. This effect can be enhanced by increasing the amplitude of the vibration. During vibration, the inertia of the water causes the large bubbles to break up into smaller bubbles and can generate longitudinal shear forces that can promote the bubbles to detach and move. Increasing the frequency can enhance this effect by shortening the period of the action. However, the vertical sinusoidal vibration does not promote the discharge of air bubbles from the flow channel out of the cell, in which the thrust and lateral shear provided by water flow is necessary. Increasing the water velocity can also generate more bubble flow. The combination of vibration and high water velocity can significantly reduce the gas concentration in the cell. Polarization data shows a 7.2% reduction in cell polarization under the experimental conditions (80 mL/min, 1.5 mm, 150 Hz) compared to the normal state. The results of this study can provide theoretical basis and experimental data for the study of bubble management methods, optimization of working conditions and improvement of operating efficiency of PEMEC.

Habitat suitability of golden mahseer young ones (Tor putitora, Hamilton 1822) in Himalayan waters, India

AbstractHabitat suitability refers to the mechanism that enables organisms to choose suitable habitats to survive. In the present study, we studied the habitat suitability of young golden mahseer (fingerlings and juveniles) in the streams of the Ramganga River, one of the prominent rivers of the western Himalaya. Different habitat types and microhabitat features were documented. Habitat suitability was evaluated by generating habitat suitability criteria curves in response to varying habitat availability and use by young golden mahseer during different seasons. Generalised linear modelling (GLM) was used to analyse environmental characteristics responsible for selecting golden mahseer habitats. We studied mahseer based on body size into two main classes, that is, fingerlings (1.5–10 cm) and juveniles (10–30 cm). Golden mahseer fingerlings preferred mean depth (0.1–0.6 m) and mean stream velocity (0–0.2 m/s) at stream reach dominated by diverse substrate compositions such as sand, gravel, and small cobbles. Similarly, juveniles preferred mean depth (0.1–1.5 m) and mean water velocity (0.1–0.5 m/s), with cobbles, bedrock, and sand dominating their habitats. The GLM results indicated that dissolved oxygen, temperature, and water velocity were the significant factors influencing habitat suitability. High dissolved oxygen positively influenced fingerlings, whereas moderate to high water velocity affected juveniles the most. Therefore, to understand the flow requirement for threatened species like golden mahseer, it is essential to characterise critical habitats and develop criteria based on habitat suitability curves.

Relationship between Water Quality & Black Flies (Diptera: Simuliidae) Abundance in Tambunan District, Sabah

A study to investigate the relationship between black flies (Simuliidae) pupa abundance and physio-chemical parameters such as velocity, water temperature, pH, dissolved oxygen, conductivity and total dissolved solid was conducted at Tambunan district, Sabah. A total of six rivers were selected as sampling stations. Five sampling points located at a distance of 5-10 meters were established in each sampling station. Sampling was conducted every fortnight for a duration of six months from October 2015 until March 2017. Samples of black flies larvae and pupae were manually collected from substrates consisting of grasses, plant roots and plastics which were found stuck in between the rocks with running water area. Water quality parameters that were measured during every sampling, include water temperature, velocity, pH, dissolved oxygen, conductivity and total dissolve solids (TDS). Results from this study showed that The Principal Component Analysis (PCA) revealed two PC’s which had eigenvalues >1.0 and together accounted for 78% total variability of the physio-chemical parameters. PC-1 which accounted 56% of variability defined a normal temperature (23-250C), high water velocity, high dissolved oxygen, low conductivity and low total dissolved solid. While PC-2 explained 22% of the variability was related to water pH. Pearson’s correlation result shows that only velocity had a significant relationship with the abundance of black flies (r=0.512, p<0.01), while other parameters did not show any significant relationship with its abundance. In conclusion, results from this study revealed that only water velocity had a significant relationship with the abundance of black flies.

Electrochemical performance study of proton exchange membrane electrolyzer considering the effect of bubble coverage

Bubble dynamics are closely related to the electrochemical performance of a proton exchange membrane electrolyzer (PEMEC). However, tiny bubbles need to be clustered together to affect the electrochemical performance of PEMEC significantly. In this paper, the effect of microscopic bubbles on macroscopic electrochemical properties were assessed by bubble coverage. The bubble dynamics, two-phase flow, and electrochemical performance were captured under different conditions using a high-speed, microscopic visualization experimental system. The results show that various factors influence the two-phase flow pattern. At 60 °C, 1.5 A/cm2 and 5 mL/min, the annular flow occupied 76.8% of the gas phase area, and when the water flow increased to 80 mL/min, the annular flow ratio decreased substantially to 2.7%. The two-phase flow of bubbles in the flow channel showed different flow patterns over time. Under the experimental conditions (60 °C, 20 mL/min, 0.8 A/cm2), the bubble flow pattern experienced the emergence of bubbles, bubble flow, segmental plug flow, annular flow, and final steady state with the occurrence times of 0.15 s, 1.5 s, 5.0 s, 10.5 s, and 21.2 s, respectively. The bubble coverage increased with current density and temperature, while it decreased with the increase of water velocity. In addition, the effects of temperature and water velocity on bubble coverage and PEMEC performance vary in principle. Specifically, higher temperature mainly improves the bubble coverage by increasing the electrochemical performance of PEMEC. In contrast, higher water velocity mainly improves the electrochemical performance of PEMEC by decreasing the bubble coverage. This study elucidates the relationship between microscopic bubbles and macroscopic electrochemical performance, contributing to a better understanding of the processes and principles of bubble effects on the electrochemical performance of PEMEC. The results may provide a theoretical basis and experimental data for operating condition optimization, operating efficiency improvement, multiphase flow study, gas diffusion layer structure, and flow field design of PEMEC.

Transverse mixing zone under dispersion in porous media: Effects of medium heterogeneity and fluid rheology

The addition of an environmental remediation modifier—polymer solution—to a Newtonian fluid expands the distribution of remediation agents injected in situ into saturated aquifers (affecting plume velocity and deformation), enhancing remediation efficiency. However, the effect of the flow properties of the polymer solution on the macroscopic transverse dispersion remains poorly understood. In this work, a transparent thin-layer two-dimensional sandbox was constructed to simulate the aquifer, and the transverse distribution range of colored solute—permanganate solution and viscous shear-thinning fluid (permanganate solution + xanthan gum)—was captured in real-time by a camera device during transport in porous media. The boundary dispersion coefficient was obtained by fitting a breakthrough curve of the boundary concentration, while the overall plume dispersion coefficient was determined via image moment analysis. The effects of fluid rheology and heterogeneity on the transverse mixing of the plume were analyzed, and the mechanism of viscoelasticity-induced transverse dispersion and mixing enhancement was summarized. The results indicated that the anisotropic stress generated by polymer fluid deformation at high water velocity increased the fluctuation and transverse distribution of the plume, while higher-viscosity polymers increased the initial extrusion swelling and additional compressive stress, covering a larger area. Xanthan gum enhanced the transverse distribution of the plume mainly through initial injection-extrusion expansion effect, viscoelastic stability of the post-injection part, and streamline crossing attributed to elastic turbulence. This study also verified that the shear-thinning fluid enhanced the effect of transverse dispersion and mixing under heterogeneous conditions, providing insights applicable to groundwater remediation.

Study on surface fabrication and drag reduction performances of gradient hydrophobic aluminum alloy

An underwater superhydrophobic (SH) surface drag reduction is an effective drag reduction method. However, drag reduction failure is likely to occur on the SH surface at high water velocity. To solve this problem, we designed an SH and hydrophilic interphase (SH-H) and gradient SH-H (GSH-H) structure on the surface of aluminum alloy by laser etching and micro-electric discharge machining (EDM) methods. The laser scanning interval of the SH segment was 10 μm while that of the hydrophobic segment was 250 μm. The hydrophilic segment was cut by micro-EDM without laser processing. The SH and hydrophobic segments were treated with fluor silane to obtain surfaces with low surface energy. In this work, the flow field characteristics of the SH-H and GSH-H model with different Re were simulated by setting a sliding wall for numerical calculation. the drag reduction ability of samples for varying Reynold number (Re) were studied in pressure difference drag-reduction channel. The simulation results show that the SH-H structure can still seal a thin gas film at Re = 4000, and has a good drag reduction effect. The experiment results show that the drag reduction on the SH-H surface was up to about 45.45%. Moreover, when soaking in water for 30 min and Re = 3500, the sample surface still had the drag reduction effect, and the prepared SH surface had good mechanical stability. It is expected that this research can provide reference and ideas for solving the problem of gas film loss on the SH surface.

Algorithm for Appropriate Design of Hydroelectric Turbines as Replacements for Pressure Reduction Valves in Water Distribution Systems

Gravity flow water distribution systems (WDSs) are used to permit water flow from an input point of highest elevation (source) to the terminal points of a system (consumers). In such WDSs, typically, there is no need for external power to maintain the flow due to the typical high gradients that exist. However, those gradients cause high water velocity and pressure to some network areas that could potentially lead to pipes bursting. Currently, the only means to regulate pressure within allowable range are Pressure Reduction Valves (PRVs). They are installed at various locations, but they cannot utilize the existing hydropower potential in terms of electrical energy production. This paper provides a methodology for hydro-turbines dimensioning, so that they mimic PRV operation in terms of pressure regulation while producing power efficiently. This includes an algorithmic process within which the proper turbine design and performance prediction are initially determined, and then, via an interconnection between EPANET and MATLAB, the hydraulic behavior of their operation within the water network is modeled and simulated. The methodology has been tested with simulations of a typical urban WDS. The results indicate that the produced turbine geometries mimic PRV action at the respective locations with more than 1% accuracy during 70% of the time (2% maximum error), while producing electric energy with hydraulic efficiency over 60%.

Metal-organic frameworks for high performance desalination through thickness control and structural fine-tuning

Two-dimensional nanoporous membranes hold great promise for the design of state-of-the-art desalination architectures to alleviate the increasing global water scarcity. Herein, by employing molecular dynamics simulations, we demonstrate the great potential of two recently reported metal-organic frameworks (MOF) membranes, namely NiIT and NiAT, as efficient desalination membranes that reach super high water flux and high salt rejection. The desalination performance of the MOF membrane is highly tunable through controlling the membrane thickness from one layer to five layers. Double layer NiIT membrane exhibits excellent salt rejection of 100% for NaCl, and meanwhile achieving high water permeability of ∼45 L/cm2/MPa/day. While for the convertible double-layer NiAT, it effectively rejects ∼96% ions with an improved water permeation of over 70 L/cm2/MPa/day. Quantitative analysis of water distribution reveals a denser water solvation shell around NiAT membrane than NiIT and a higher water velocity through the nanopore of NiAT than that of NiIT, contributing to the enhanced water permeability. Through calculating free energy for water/ions translocating through two membranes, a clear energy barrier is observed for ions to penetrate through the sub-nanosized pores in both membranes, leading to the high salt rejection. The present study suggests that these two MOF membranes can serve as a promising semipermeable membrane for energy-efficient desalination which is highly prospective in industrial applications.

Dispersal and transport of microplastic particles under different flow conditions in riverine ecosystem.

Microplastic (MP) pollution is a global issue owing to its potential threats to ecosystems and human health. MP pollution in river ecosystems is widely investigated, but the transport process under different hydrological conditions remain unclear. In this study, an approach of particle tracking in conjunction with hydrodynamic modeling was developed to investigate the dispersal and transport processes of microplastic particles in riverine ecosystem. The concentration and dispersal pattern of polyamide (PA), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) particles under base flow and flood events with recurrence intervals of 10-year, 20-year and 50-year were identified. Results indicated that rainfall intensity had a significant impact on the microplastic transport in rivers. Higher suspension concentration and lower sedimented concentration were observed in high flow periods, and the sedimented concentration showed a slow increasing trend in the flood recession stage. High water velocity facilitated the microplastic particles to be migrated for a longer distance, and high water flow was conducive to transport more microplastics from source points. Besides, microplastic particles with high density had worse mobility in water and more prone to deposition. PET were likely to be transported for a relatively shorter distance, while PP had higher mobility and took less time to reach the same simulation point. This study put forward an effective approach to understand the transport of MPs in the river. The results obtained are useful to identify pollution hotspots and track pollution paths.

The influence of polymer bearing material and lubricating grooves layout on wear of journal bearings lubricated with contaminated water

The goal of the present paper is to investigate wear properties of journal sliding bearing operating in the conditions of contaminated water lubrication. Several bearing materials and bearing sleeve designs (differing in the axial grooves position and their shape) were tested experimentally under typical operating conditions in a dedicated test rig, which was equipped with a lubricating system, enabling lubrication with contaminated water. Results of the tests show that water contamination has a strong impact on the wear of the bearing system elements. It was revealed that some of the tested materials are beneficial in such demanding conditions and demonstrate lower wear rates. The design of the bearing bush also seems to have an impact on the wear, because bearings of different designs made from the same material demonstrated differences exceeding 100 %. Higher water velocity in the lubricating grooves helps to minimize the wear of the stainless steel shaft. This was also confirmed by numerical simulations.

Development of Four Nossel Cross Flow Turbine

ross flow turbines are widely used as turbines for driving micro-scale hydropower plants in rural areas, but their efficiency is still low because cross flow turbines only use one nozzle. The utilization of the potential energy of water is not optimal yet to be converted into pressure and kinetic energy of water in the nozzles with high water velocity hitting the turbine blades. The problem of cross flow turbines with one nozzle has an uneven flow of water to the turbine blades, and it is not effective in converting potential energy into power in the turbine. The purpose of this research is to develop a four-nozzle Cross Flow turbine and test its performance. The method used is to conduct experimental testing in a laboratory that tests the performance of a cross flow turbine using four nozzles. A cross flow turbine with four nozzles has better performance than a cross flow turbine using only one nozzle. The results obtained that the cross flow turbine with four nozzles where the water jets out of the nozzle is more evenly distributed and the flow of water enters the turbine blade runner, resulting in a good impulse reaction in the blades. The conclusion is that the performance of the four nozzle cross flow turbine is able to produce higher turbine rotation, power and efficiency.

Diffusion characteristics and reinforcement effect of cement slurry on porous medium under dynamic water condition considering infiltration

Grouting methods are known to effectively remediate the groundwater inrush in tunnels with weak water-rich sand layers. However, the diffusion characteristic of cement slurry flowing in rock and soil media with flowing water is one of the many critical issues that still remain unsolved. The cement-based grouting material diffusion characteristics of water in rock, considering four grouting parameters of water-cement ratio, water flow speed and fractal dimension of particle mass, were researched through a series of experiments such as cement particle filtration, nuclear magnetic resonance and diffusion test. Then compressive strength, scanning electron microscope(SEM) and mercury intrusion porosimetry(MIP) were performed on consolidated specimens to examine physico-chemical bonding mechanisms characteristics. The results indicate that 1) The viscosity of the effluent at the test point varies with the increase of water discharge velocity with different water cement ratio. When the water cement ratio is low, the viscosity of effluent increases first and then decreases with the increase of water flow rate. For high water cement ratio, the viscosity of the same test point decreases with the increase of water velocity. 2) The porosity of the consolidation with a low water velocity is lower than that of the media with a high water velocity within 4 m of the injection site. However, when it exceeds 4 m, the porosity has the opposite trend. 3) In the range of 0.3 ∼ 0.4 m, the grouting pressure at middle and low velocity is higher than that of high velocity. Beyond this range, the trend is reversed. 4) When cement slurry flows in particles, its pressure attenuation law is not affected by the state of dynamic water and is only related to the fractal dimension of particles. Its pressure attenuation decreases sharply with the increase of distance, when cement slurry flows in the particle mass with higher fractal dimension. Nevertheless, the flow pressure of cement slurry decreases slowly with the increase of distance at low fractal dimension. 5) The compressive strength of the consolidated body of cement and sand decreases with the increase of water-cement ratio and distance. Microstructural changes in sand fabric indicate that cement grouting material modified the porous network of consolidated sand. The pores were filled and particles were bonded by hydration product of cement.

A scaled Denil fishway for upstream passage of Arctic Grayling

Denil fishways have been used with varying success to help fish pass impediments to upstream passage such as low head dams or irrigation diversion structures. They have been tested for hydraulic and fish passage performance in laboratory and field settings, usually with only minor modifications to the fishway geometry or dimensions. We tested a reduced (0.6) scale prototype of the standard-sized Denil fishway to determine if the smaller fishway, which requires less water flow, would successfully pass Arctic Grayling (Thymallus arcticus). The scaling factor was informed by analyzing previously published scalable Denil fishway rating equations. A prototype was tested in an open-channel flume using 8 treatments with 3 trials per treatment and 8 fish per trial. Each treatment had a prescribed combination of headwater and tailwater depths. Overall, 93% (178/191) of the fish volitionally entered the fishway and of these 91% (162/178) passed successfully. Entrance and passage were reduced only in treatments with the highest hydraulic slopes and highest water velocities at the downstream end of the fishway (i.e. with high headwater depths and low tailwater depths). The 0.6-scaled Denil fishway is likely a good alternative to standard-sized Denil fishways to enhance upstream mobility of Arctic Grayling in small, water-limited streams.

Opening the Door: Alosa pseudoharengus (Alewife) Passage through Tide Gates in Two Adjacent Rivers on the Chignecto Isthmus, Bay of Fundy, Canada

We assessed Alosa pseudoharengus (Alewife) upstream passage during 2016–2019 spawning runs using radio frequency identification (RFID) tracking through a periodically submerged and a constantly submerged top-hinged tide gate in the LaPlanche and Missaquash rivers, respectively, on the Chignecto Isthmus, Canada. First detection of individuals tagged in previous years (i.e., returnees) revealed synchronous upstream run timing in both rivers during 2015 and 2018. Greater delays of migrants attempting passage through the periodically submerged tide gate prompted temporary removal of 1 flapper door during 2016–2019 runs. During a 7-day period following door removal, the number of individuals passing per day increased 4- to 6-fold during 2016–2017 and less than 2-fold during 2018–2019. More than 80% of returnees passed the periodically submerged gate following door removal, decreasing mean delay to less than that of migrants attempting passage of the constantly submerged gate. Most individuals passed the periodically submerged gate during mid-flood daily tide phases and none passed during low-tide outflow due to high water velocities. Passage of the constantly submerged gate occurred during all tide phases, with 77% passing during ebb and low tides. The constantly submerged tide gate provided greater windows of opportunity, resulting in relatively shorter delays compared to the periodically submerged tide gate. Long-term monitoring in this study highlighted the effectiveness of temporary and/or adaptive mitigation when addressing issues in river connectivity and fish passage.

Simulated degradation of low-density polyethylene and polypropylene due to ultraviolet radiation and water velocity in the aquatic environment

Low-density polyethylene (LDPE) and polypropylene (PP) are the two main polymers with extensive applications. It might lead to plastic pollution and degradation in the aquatic environment. Former laboratory simulation studies of plastic degradation have been presented. However, most of the studies were only applied a single degradation agent without specific environmental conditions, which indicated a research gap. This research aimed to investigate LDPE and PP degradation under the influence of UV radiation and water velocity with specific environmental conditions. Five reactors of simulated aquatic environments were adjusted to desire calculated UV B dose of 158.98–438.91 W.S/cm2 and water velocity variations of the Surabaya River, one of Indonesia’s urban rivers that has been polluted by microplastics. The water velocity was set in high (0.3–0.6 m/s) and low ones (0.1–0.3 m/s) to represent the fluctuated river discharge at rain and dry seasons. Total simulation time of 480 h (8 h/day for 60 days simulation) has initiated LDPE and PP degradation. LDPE experienced more weight loss (3.07%) under the combined exposure of UV and high water velocity, than PP (2.37%) under high water velocity. Synergetic effects of photodegradation, physical-mechanical, and hydrolysis degradation mechanisms could affect more severe crack tip formation of LDPE and PP rather than in single agent simulation. Major surface morphology deterioration of LDPE and PP, changes in transmittance intensities, carbonyl index in this study have revealed the importance of combined exposure of UV radiation and water velocity to plastic degradation in the aquatic environment.