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Table 1 Intervention, fish injury/impact, and general hydropower terms and definitions used in the systematic review

From: What are the relative risks of mortality and injury for fish during downstream passage at hydroelectric dams in temperate regions? A systematic review

 BypassA structure that collects fish upstream and deposits fish downstream of the facility. Typically used for juveniles. Several bypass types, but surface and turbine bypasses are most common
 DamStructure for impounding water. Dam height generates head pressure for the turbines
 Draft tubeA column (structure) from the turbine outlet to the tailrace that water flows through
 Exclusionary deviceStructure(s) to prevent or divert fish entrance/passage. Often used to divert fish from turbines into bypasses. Common structures include various screens
 General infrastructureCategory used to capture studies that evaluated entrainment or impingement through > 1 components of a hydroelectric facility. Within the meta-analysis, this category encompassed lab studies that simulate conditions fish may experience (e.g., shear forces) through various infrastructure
 LouverA structure of set angled bars or slats that can be used to divert/guide fish towards bypasses or sluices. These structures do not exclude fish like screens, rather alter hydraulic flow patterns and/or streamflow to guide fish
 Outlet worksA combination of structures designed to control reservoir water levels and/or water release for hydropower facility operations. Structures can include intake towers, outlet tunnels and/or conduits, control gates, and discharge channels. Intake structures can have trash racks or other purposefully designed fish intakes
 PenstockAn intake structure (channel, pipe) that leads into the turbines
 ScreenAn exclusionary device to prevent fish from entering a structure (e.g., turbine) or divert fish towards a bypass
 SpillwayAn outlet or channel in a dam or reservoir that discharges surplus water downstream of a dam. Spillways can vary by design (e.g., channel type, height)
 SluicewaysA surface channel extending from the forebay to the tailrace designed to allow ice and debris to pass
 Surface bypassesStructures that spill minimal amounts of water to facilitate passage over a dam. Several types exist (see [23]). Fish are collected and pass through a series channels that discharges downstream of the facility into the tailrace. Typically used for juvenile salmonids, taking advantage of their surface-oriented swimming behaviour
 Trash rackA type of exclusionary device designed to keep debris out of turbine intakes, but can be used to guide fish to “safer” passage routes such as bypasses and sluices
 Turbine (hydraulic)A structure that converts the energy of flowing water into mechanical energy. There are several turbine types with different configurations, the most common are Francis and Kaplan (see definitions below)
 Kaplan turbineAn “axial”, vertical, propeller-like turbine used for lower pressure heads (less than 100 m). Smaller in overall size (relative to Francis), typically has 4 to 8 adjustable blades and a specific running speed ranging 250 to 850 rpm
 Francis turbineA “radial” turbine used for higher pressure heads (100 to 500 m). Larger in overall size (relative to Kaplan), typically has 16 to 24 fixed blades and a specific running speed of 50 to 250 rpm
 Turbine bypassA structure that fish can enter from the gatewell, bypasses the turbines and powerhouse through a series of channels, and discharges downstream into the tailrace. Typically used for juvenile salmonids
Fish injuries/impacts
 AbrasionDamage to skin and/or scales
 Blade strikeTurbine blade striking a fish. Can result in injuries/mortality from grinding (depending on blade spacing, small fish more prone to this), bruising, and cuts of varying severity (superficial, mortal wounding)
 BarotraumaDamage caused from exposure to rapid changes in barometric pressure, typically during turbine passage. The most common injuries/mortalities are related to swim bladder ruptures. In the presence of high total dissolved gasses, rapid pressure changes can cause gas embolisms in tissues/organs and other symptoms of gas bubble disease
 DescalingScale loss. Often expressed as a percentage of the scale loss on the whole fish (e.g., 20% scale loss)
 EntrainmentWhen fish (non-) volitionally pass through hydropower infrastructure
 HemorrhageBleeding, blood loss
 ImpingementWhen a fish becomes pinned/trapped against an infrastructure
 CavitationFormation of gas bubbles in water, which when collapsed generate a pressure wave that can cause ill effects for fish in close proximity
 Mechanical effectsDamage (injury/mortality) caused from fish physically interacting with structures (e.g., blade strike)
 Pressure effectsRapid changes in pressure (perpendicular to surface, dorsoventral) during passage that can cause fish damage
 Shear effectsRapid changes in pressure (parallel to surface, anteroposterior) during passage that can cause fish damage
 Turbulence effectsDamage (injury/mortality) to fish caused by turbulent water (irregular movement of water)
General terms
 ForebayImpoundment area directly above a hydropower facility
 HeadDifference in elevation between two water levels (e.g., reservoir water level and tailrace). There are various operational head definitions (see [34])
 Passive Integrated Transponder (PIT) tagA small tag implanted into a fish that transmits a unique code when activated. Can be used to track fish passage and survival through specific routes and river systems
 TailraceA channel downstream of turbine outlets discharged water flows away from the facility
 TelemetryA system for tracking fish movements through specific routes at a facility as well as along watercourses. Common methods are acoustic, radio, and passive integrated transponder (PIT) tag telemetry
  1. Most of the hydropower terms are adapted from OTA [33], ASCE [34], and Čada et al. [35], see these publications for a comprehensive list of definitions and hydropower related terms