Skip to main content

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

Term

Description

Interventions

 Bypass

A 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

 Dam

Structure for impounding water. Dam height generates head pressure for the turbines

 Draft tube

A column (structure) from the turbine outlet to the tailrace that water flows through

 Exclusionary device

Structure(s) to prevent or divert fish entrance/passage. Often used to divert fish from turbines into bypasses. Common structures include various screens

 General infrastructure

Category 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

 Louver

A 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 works

A 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

 Penstock

An intake structure (channel, pipe) that leads into the turbines

 Screen

An exclusionary device to prevent fish from entering a structure (e.g., turbine) or divert fish towards a bypass

 Spillway

An 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)

 Sluiceways

A surface channel extending from the forebay to the tailrace designed to allow ice and debris to pass

 Surface bypasses

Structures 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 rack

A 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 turbine

An “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 turbine

A “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 bypass

A 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

 Abrasion

Damage to skin and/or scales

 Blade strike

Turbine 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)

 Barotrauma

Damage 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

 Descaling

Scale loss. Often expressed as a percentage of the scale loss on the whole fish (e.g., 20% scale loss)

 Entrainment

When fish (non-) volitionally pass through hydropower infrastructure

 Hemorrhage

Bleeding, blood loss

 Impingement

When a fish becomes pinned/trapped against an infrastructure

 Cavitation

Formation of gas bubbles in water, which when collapsed generate a pressure wave that can cause ill effects for fish in close proximity

 Mechanical effects

Damage (injury/mortality) caused from fish physically interacting with structures (e.g., blade strike)

 Pressure effects

Rapid changes in pressure (perpendicular to surface, dorsoventral) during passage that can cause fish damage

 Shear effects

Rapid changes in pressure (parallel to surface, anteroposterior) during passage that can cause fish damage

 Turbulence effects

Damage (injury/mortality) to fish caused by turbulent water (irregular movement of water)

General terms

 Forebay

Impoundment area directly above a hydropower facility

 Head

Difference 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) tag

A 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

 Tailrace

A channel downstream of turbine outlets discharged water flows away from the facility

 Telemetry

A 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