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Discharge and channel geometry control velocity and bed shear stress within a reach. Channel roughness (e.g., riffles, pools) and ice cover in winter moderates velocity and shear stress at the bed. This study evaluated velocity profiles across a channel segment with variable bed roughness (e.g., riffles, pools) to determine changes in the position of maximum velocity, maximum velocity magnitude, and resulting bed shear stress estimates when ice cover was present. Using acoustic doppler velocimeter (ADV) and acoustic doppler current profiler (ADCP) high resolution velocity profiles were collected during ice cover, open water, and open water with significant increases in vegetation cover through a riffle‐pool sequence in a low‐order channel in southern Ontario Canada in the first half of 2021. Key findings were that in five of the seven cross‐sections, flow direction was significantly different when ice was present. Additionally, maximum velocities were closer to the bed during ice cover, a common finding in modelling and experimental work, and is confirmed in this field setting. Although maximum velocity magnitudes were not significantly different, derived bed shear stress values under ice were larger. Specifically, under ice conditions, riffle bed shear stress ranged 0–16 N/m2 compared to 0–9 N/m2 in ice free conditions. In the pool, bed shear stress ranged 0–6 N/m2 under ice cover, and 0–5 N/m2 in ice free conditions. Further, as flow levels increased through the spring and summer, this coincided with increased in‐stream vegetation cover, which decreased flow velocities near the bed, and thus decreased bed shear stresses to less than 1 N/m2 in both the riffle and pool sections. The findings indicate that channel evolution processes may be more intense during lower‐stage winter flows when ice is present and has significant implications for channel design, restoration and management strategies used in small channels impacted by ice cover. [ABSTRACT FROM AUTHOR]

Objective: Regulatory legislation in both the United States and Canada requires water users with medium to high intake volumes to monitor entrainment losses to determine effects and to assess potential mitigation strategies to reduce harm to fish. Recent studies have recommended the use of both increased sampling frequency and sampling volume to characterize fish entrainment for large power plants on the Great Lakes. There is little doubt that increasing the flow rate and volume of water collected for sampling reduces the uncertainty in estimates of annual entrainment. Depending on the type of pump and the pumping flow rate used for entrainment sampling, considerable damage to fish larvae can occur. A screw‐type centrifugal pump has many qualities that make it ideal for entrainment sampling, but it has not yet been used as a sampling device for fish entrainment applications at power plants or other large industrial water users. The objective of this study was to determine mortality of entrainable fish eggs and larvae due to passage through a screw‐type centrifugal pump. Methods: In a laboratory setting, Lake Trout Salvelinus namaycush eggs and larvae, Lake Whitefish Coregonus clupeaformis eggs, and Rainbow Trout Oncorhynchus mykiss juveniles were passed through a screw‐type centrifugal pump at three treatment flow rates: 39.5, 47.3, and 59.1 m3/h. Fish and eggs were monitored for mortality posttreatment and again at 24 and 48 h. Result: Across treatments, very few mortalities were observed. Species specific moralities were four larval Lake Trout, one Lake Whitefish egg, and one juvenile Rainbow Trout. No mortality was observed for Lake Trout eggs. Conclusion: The present study identified high egg and larval survival (≥99%) after passage through a screw‐type centrifugal pump. High survival reduces error associated with identification and counting of entrained organisms, which provides more accurate estimates of annual entrainment losses. Impact statementA screw‐type centrifugal impeller pump results in high survival of entrainable fish (eggs and larvae), which reduces error associated with estimating fish mortality due to entrainment. Reduced error improves entrainment mortality estimates that may be used to develop compensation strategies to mitigate loss of fish from aquatic systems. [ABSTRACT FROM AUTHOR]

Temperature variations could potentially impact flotation performance, leading to operational and economic issues. Several historical and currently operating plants across Canada have reported seasonal metal losses as one of their major challenges. Improvements in flotation efficiency at cold temperatures are important for the sustainable development of the industry, especially in view of expanding mining operations to the north and the increasing impact of climate change-originated weather extremes on mining operations. To better understand the driving mechanisms of the seasonal metallurgical variation, the degree of vulnerability of froth flotation to fluctuations in temperature, and to develop recommendations addressing seasonally driven losses, a series of mono-mineral flotation tests were conducted. The observed variations in yield and recovery kinetics for different sulfide minerals follow a similar pattern: higher recovery and slower kinetics at lower temperatures, and lower recoveries and faster kinetics at higher temperature conditions. Following the results of the flotation tests, foam height and stability were investigated at different temperatures to explain the observed variations. A high correlation between changes in mono-mineral flotation behavior and foam properties with temperature was revealed. [ABSTRACT FROM AUTHOR]

Efforts are underway to re‐evaluate the use of existing instream infrastructure (e.g., weirs, water control dams) for the purposes of hydroelectric generation, with new very low head turbine technology that is purportedly "fish friendly" making retrofitting a viable option. This is the case at Wasdell Falls on the Severn River, ON, Canada, where the first very low head (VLH) turbines in Canada were put into operation at a long‐standing low‐head dam site. There is little information regarding fish usage of areas upstream from these structures and how this may relate to entrainment risk. Therefore, we assessed the risk of entrainment based on fish use of the forebay areas upstream from the infrastructure, including the forebay of three operating VLH turbines. Acoustic telemetry was used to determine movements and entrainment events of eight north temperate fish species. Entrainment through the VLH turbines did not occur over the course of one year, however, several fish did move downstream via other paths (e.g., over the water control structure). Forebay use was exclusive to rock bass, smallmouth bass, northern pike and largemouth bass, whereas channel catfish, walleye, white sucker and pumpkinseed avoided the forebay. When near the dam, fish tended to select deeper areas located away from the VLH forebay. Fish use of the VLH forebay was limited to brief forays indicating exploratory movements rather than prolonged residence. The findings suggest that entrainment risk at this VLH turbine site is low for the species and life stages studied. [ABSTRACT FROM AUTHOR]

In Canada, the Fisheries Act requires all water takers to avoid, mitigate and offset fish losses. To satisfy the act's requirements, operators of power plants are required to undertake habitat restoration projects to compensate for fish impinged and entrained at cooling water intake structures. Scaling the quantity of restoration needed, and measuring whether adequate compensation has been achieved, requires a metric that expresses the losses and gains in comparable units. Development of such a metric is especially difficult in the case of power plants, because the losses often consist of a mix of species and life stages that are very different from those produced by technically feasible restoration projects. This paper documents the method that has been developed for quantifying offsets for impingement and entrainment at the Bruce Generating Stations on the eastern shore of Lake Huron, and demonstrates how the method is being used to estimate the offset to be provided by removal of a dam on the nearby Saugeen River. [ABSTRACT FROM AUTHOR]