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Other glossaries of fisheries terms are available from North Carolina Division of Marine Fisheries and from the United Nations Fisheries and Agriculture Organization.
(The FAO glossary does not work with all web browsers.)

Annual operating plan -- A yearly plan for operating reservoirs on the Columbia River. Such a plan is specifically required by the Columbia River Treaty and by the Pacific Northwest Coordination Agreement.

Approach velocities -- Water velocities at or near the face of a fish screen.

Appropriate -- To authorize the use of a quantity of water to an individual requesting it.

Arch Dam -- Curved masonry or concrete dam, convex in shape upstream, that depends on arch action for its stability; the load or water pressure is transferred by the arch to the Abutments.

Attraction -- Drawing fish to dam fishways or spillways through the use of water flows.

Augmentation (of stream flow) -- Increasing steam flow under normal conditions, by releasing storage water from reservoirs.

Average megawatt (aMW) -- The average amount of energy (in megawatts) supplied or demanded over a specified period of time; equivalent to the energy produced by the continuous operation of one megawatt of capacity over the specified period.

Barrier -- A physical block or impediment to the movement or migration of fish, such as a waterfall (natural barrier) or a dam (man-made barrier).

Baseload -- In a demand sense, a load that varies only slightly in level over a specified time period. In a supply sense, a plant that operates most efficiently at a relatively constant level of generation

Blocked areas -- Areas in the Columbia River Basin where hydroelectric projects have created permanent barriers to anadromous fish runs. These include the areas above Chief Joseph and Grand Coulee dams, the Hells Canyon Complex and other smaller locations.

Bonneville Power Administration (Bonneville) -- The sole federal power marketing agency in the Northwest and the region's major wholesaler of electricity. Created by Congress in 1937, Bonneville sells power to public and private utilities, direct service customers, and various public agencies in the states of Washington, Oregon, Idaho, Montana west of the Continental Divide, (and parts of Montana east of the Divide) and smaller adjacent areas of California, Nevada, Utah and Wyoming. The Northwest Power Act charges Bonneville with additional duties related to energy conservation, resource acquisition, and fish and wildlife.

Buttress Dam -- A dam consisting of a watertight upstream face supported at intervals on the downstream side by a series of buttresses.

Bypass system -- A channel or conduit in a dam that provides a route for fish to move through or around the dam without going through the turbine units.

Canal -- A constructed open channel for transporting water.

Catchment -- (1) The catching or collecting of water, especially rainfall. (2) A reservoir or other basin for catching water. (3) The water thus caught.

Check dam -- A small dam constructed in a gully or other small water course to decrease the streamflow velocity, minimize channel erosion, promote deposition of sediment and to divert water from a channel.

Collection and bypass system -- A system at a dam that collects and holds the fish approaching the dam for later transportation or moves them through or around the dam without going through the turbine units.

Dam -- A concrete or earthen barrier constructed across a river and designed to control water flow or create a reservoir.

Deflector screens/diversion screens -- Wire mesh screens placed at the point where water is diverted from a stream or river. The screens keep fish from entering the diversion channel or pipe.

Demand -- The rate at which electric energy is used, whether at a given instant, or averaged over any designated period of time.

Descaling -- A condition in which a fish has lost a certain percentage of scales.

Dewatering -- Elimination of water from a lake, river, stream, reservoir, or containment.

Dike -- (1) (Engineering) An embankment to confine or control water, especially one built along the banks of a river to prevent overflow of lowlands; a levee. (2) A low wall that can act as a barrier to prevent a spill from spreading. (3) (Geology) A tabular body of igneous (formed by volcanic action) rock that cuts across the structure of adjacent rocks or cuts massive rocks.

Discharge -- Volume of water released from a dam or powerhouse at a given time, usually expressed in cubic feet per second.

Dissolved gas concentrations -- The amount of chemicals normally occurring as gases, such as nitrogen and oxygen, that are held in solution in water, expressed in units such as milligrams of the gas per liter of liquid. Supersaturation occurs when these solutions exceed the saturation level of the water (beyond 100 percent).

Dissolved Oxygen (DO) -- The amount of free (not chemically combined) oxygen dissolved in water, wastewater, or other liquid, usually expressed in milligrams per liter, parts per million, or percent of saturation.

Diversion Dam -- A barrier built to divert part or all of the water from a stream into a different course.

Draft -- Release of water from a storage reservoir.

Drawdown -- The release of water from a reservoir for power generation, flood control, irrigation or other water management activity.

Earthfill or Earth Dam -- An embankment dam in which more than 50 percent of the total volume is formed of compacted fine-grained material obtained from a borrow area (i.e., excavation pit).

Elevation -- Height in feet above sea level.

Embankment Dam -- A dam structure constructed of fill material, usually earth or rock, placed with sloping sides and usually with a length greater than its height.

Energy -- The ability to work (i.e., exert a force over distance). Energy is measured in calories, joules, KWH, BTUs, MW-hours, and average MWs.

Energy content curves (ECC) -- A set of curves that establishes limits on the amount of reservoir draw-down permitted to produce energy in excess of FELCC.

Entrainment -- (Streams) The incidental trapping of fish and other aquatic organisms in the water, for example, used for cooling electrical power plants or in waters being diverted for irrigation or similar purposes.

Evaporation -- The physical process by which a liquid (or a solid) is transformed to the gaseous state. In Hydrology, evaporation is vaporization that takes place at a temperature below the boiling point.

Federal Energy Regulatory Commission (FERC) -- The Commission issues and regulates licenses for construction and operation of non federal hydroelectric projects and advises federal agencies on the merits of proposed federal multipurpose water development projects.

Federal project operators and regulators -- Federal agencies that operate or regulate hydroelectric projects in the Columbia River Basin. They include the Bonneville Power Administration, the Bureau of Indian Affairs, the Bureau of Reclamation, the Corps of Engineers and the Federal Energy Regulatory Commission.

FELCC -- Firm energy load carrying capability (FELCC) is the amount of energy the region's generating system, or an individual utility or project, can be called on to produce on a firm basis during actual operations. FELCC is made up of both hydro and non-hydro resources, including power purchases.

Fill Dam -- Any dam constructed of excavated natural materials or of industrial waste materials.

Firm energy -- the amount of energy that can be generated given the region's worst historical water conditions. It is energy produced on a guaranteed basis.

Fish flows -- "Artificially increased flows in the river system called for in the fish and wildlife program to quickly move the young fish down the river during their spring migration period. (See "water budget.")"

Fish guidance efficiency (FGE) -- The proportion of juvenile fish passing into the turbine intakes that are diverted away from the turbines and into bypass facilities.

Fish ladder -- See Fishway.

Fish Passage Center -- Part of the water budget program, the center plans and implements the annual smolt monitoring program; develops and implements flow and spill requests; and monitors and analyzes research results to assist in implementing the water budget. (See water budget.)

Fish passage efficiency (FPE) -- The proportion of juvenile fish passing a project through the spillway, sluiceway, or juvenile bypass system, as opposed to passing through the turbines.

Fish passage facilities -- Features of a dam that enable fish to move around, through, or over without harm. Generally an upstream fish ladder or a downstream bypass system.

Fish passage managers -- Located at the Fish Passage Center, the two fish passage managers are responsible for the specific planning, implementation and monitoring activities of the Center aimed at helping fish on their migratory routes in the Columbia River Basin. One manager is designated by a majority of the federal and state fish and wildlife agencies, and the other manager is designated by a majority of the Columbia River Basin Indian tribes. (See Fish Passage Center.)

Fish screen -- A screen across the turbine intake of a dam, designed to divert the fish into the bypass system.

Fishway -- A device made up of a series of stepped pools, similar to a staircase, that enables adult fish to migrate up the river past dams.

Fixed drawdown period -- The late summer and fall when the volume of the next spring runoff is not yet known, and reservoir operations are guided by fixed rule curve based on historical streamflow patterns.

Flow augmentation -- Increased flow from release of water from storage dams.

Flume -- (1) A narrow gorge, usually with a stream flowing through it. (2) An open artificial channel or chute carrying a stream of water, as for furnishing power, conveying logs, or as a measuring device.

Forebay -- The part of a dam's reservoir that is immediately upstream from the powerhouse.

Forebay guidance net -- A large net placed in the forebay of a dam to guide juvenile fish away from the powerhouse.

Full pool -- The maximum level of a reservoir under its established normal operating range.

Gallery -- "(1) A passageway within the body of a dam or abutment; hence the terms "grouting gallery","inspection gallery," and "drainage gallery." (2) A long and rather narrow hall; hence the following terms for a power plant: "valve gallery,","transformer gallery," and "busbar gallery."

Gallons per minute (Gpm) -- A unit used to measure water flow.

Gas Supersaturation -- The overabundance of gases in turbulent water, such as at the base of a dam spillway. Can cause fatal condition in fish similar to the bends.

Generation -- Act or process of producing electric energy from other forms of energy. Also refers to the amount of electric energy so produced.

Generator -- A machine that changes water power, steam power, or other kinds of mechanical energy into electricity.

Gravity Dam -- A dam constructed of concrete and/or masonry that relies on its weight for stability.

Gravity feed system -- A system that provides flow in a channel or conduit through the use of gravity.

Headgate -- The gate that controls water flow into irrigation canals and ditches. A watermaster regulates the headgates during water distribution and posts headgate notices declaring official regulations.

Headworks -- A flow control structure on an irrigation canal.

Hydraulic head -- The vertical distance between the surface of the reservoir and the surface of the river immediately downstream from the dam.

Hydroelectricity (Hydroelectric power) -- The production of electric power through use of the gravitational force of falling water.

Hydropower system -- The hydroelectric dams on the Columbia River and its tributaries.

Impoundment -- A body of water formed behind a dam.

In-lieu energy -- Energy provided by a reservoir owner instead of water to which a downstream party is entitled.

Inflow -- Water that flows into a reservoir or forebay during a specified period.

Intake -- The entrance to a turbine at a dam, diversion works, or pumping station.

Intake traveling screens -- See turbine intake screens.

Interim spill -- The spilling of water over John Day, The Dalles, Bonneville, Lower Monumental and Ice Harbor dams to aid fish passage. This method will be used until permanent solutions to juvenile fish passage problems are developed.

Juvenile transportation -- Collecting migrating juvenile fish and transporting them around the dams using barges or trucks.

KAF -- A thousand acre feet, same as .504 thousand second foot days.

KCFS -- A measurement of water flow equivalent to 1,000 cubic feet of water passing a given point for an entire second.

Kcfs-month -- One kcfs-month is a flow of 1,000 cubic feet per second for one month or 0.0595 million acre-feet.

Kilowatt (KW) -- The electrical unit of power which equals 1,000 watts or 1.341 horsepower.

Kilowatt-hour (kWh) -- A basic unit of electrical energy that equals one kilowatt of power applied for one hour.

KSFD -- A volume of water equal to 1,000 cubic feet of water flowing past a point for an entire day. Same as 1.98 FAF.

Load -- The amount of electric power or energy delivered or required at any specified point or points on a system.

Load shaping -- The adjustment of storage releases so that generation and load are continuously in balance.

Lock -- A chambered structure on a waterway closed off with gates for the purpose of raising or lowering the water level within the lock chamber so ships, boats, and tugs/barges can move from one elevation to another along the waterway.

Low-head dam -- A dam at which the water in the reservoir is not high above the turbine units.

MAF -- Million acre feet. The equivalent volume of water that will cover an area of one million acres to a depth of one foot. One MAF equals 1,000 KAF.

Mainstem passage -- The movement of salmon and steelhead around or through the dams and reservoirs in the Columbia and Snake rivers.

Mainstem survival -- The proportion of anadromous fish that survive passage through the dams and reservoirs while migrating in the Columbia and Snake rivers.

Masonry Dam -- A dam constructed mainly of stone, brick, or concrete blocks that may or may not be joined with mortar. A dam having only a masonry facing should not be referred to as a masonry dam.

Mechanical bypass systems -- See bypass system.

Megawatt-hour (MWh) -- A unit of electrical energy equal to one megawatt or power applied for one hour.

Megawatts (MW) -- A megawatt is one million watts or one thousand kilowatts, a measure of electrical power or generating capacity. A megawatt will typically serve about 1,000 people. The Dalles Dam produces an average of about 1,000 megawatts.

Mid-Columbia dams -- Dams owned by the mid-Columbia Public Utility Districts. They include Wells, Rocky Reach, Rock Island, Wanapum and Priest Rapids dams.

Mid-Columbia Public Utility Districts (PUDs) -- Public Utility District No. 1 of Grant County, Public Utility District No. 2 of Chelan County and Public Utility District No. 1 of Douglas County.

Minimum flow level -- The level of stream flow sufficient to support fish and other aquatic life; to minimize pollution; or to maintain other instream uses such as recreation and navigation.

Minimum operating pool -- The lowest water level of an impoundment at which navigation locks can still operate.

Mitigating measures -- Modifications of actions that (1) avoid impacts by not taking a certain action of parts of an action; (2) minimize impacts by limiting the degree or magnitude of the action and its implementation; (3) rectify impacts by repairing, rehabilitating, or restoring the affected environment; (4) reduce or eliminate impacts over time by preservation and maintenance operations during the life of the action; or (5) compensate for impacts by replacing or providing substitute resources or environments.

Mitigation -- The act of alleviating or making less severe. Generally refers to efforts to alleviate the impacts of hydropower development to the Columbia Basins salmon and steelhead runs.

Monitor -- To systematically and repeatedly measure conditions in order to track changes.

Mortality -- The number of fish lost or the rate of loss.

Nitrogen Supersaturation -- A condition of water in which the concentration of dissolved nitrogen exceeds the saturation level of water. Excess nitrogen can harm the circulatory system of fish.

Northwest power act -- The Pacific Northwest Electric Power Planning and Conservation Act of 1980 (16 U.S.C. 839 et seq.), which authorized the creation of the Northwest Power and Conservation Council and directed it to develop this program to protect, mitigate and enhance fish and wildlife, including related spawning grounds and habitat on the Columbia River and its tributaries.

Northwest Power Pool Coordinating Group -- An operating group made up of BPA, the Corps, Reclamation, and public and private generating utilities in the Northwest. One of the group's functions is administering the Pacific Northwest Coordination Agreement.

Nutrient cycling -- Circulation or exchange of elements such as nitrogen and carbon between nonliving and living portions of the environment.

Offpeak hours -- Period of relatively low demand for electrical energy, as specified by the supplier (such as the middle of the night).

Operating year -- The 12 month period from August 1 through July 31.

Outflow -- The water that is released from a project during the specified period.

Pacific Northwest Utilities Conference Committee (PNUCC) -- A group formed by Pacific Northwest utilities officials in order to coordinate policy on Pacific Northwest power supply issues and activities. PNUCC lacks contractual authority, but it plays a major role in regional power planning through its Policy; Steering; Fish and Wildlife; and Lawyers committees, and the Technical Coordination Group. PNUCC publishes the Northwest Regional Forecast, containing information on regional loads and resources.

Passage -- The movement of migratory fish through, around, or over dams, reservoirs and other obstructions in a stream or river.

Peak flow -- Refers to a specific period of time when the discharge of a stream or river is at its highest point.

Peak load -- The maximum electrical demand in a stated period of time.

Power peaking -- The generation of electricity to meet maximum instantaneous power requirements; usually refers to daily peaks.

Powerhouse -- A primary part of a hydroelectric dam where the turbines and generators are housed and where power is produced by falling water rotating turbine blades.

Project -- Run-of-river or storage dam and related facilities; also a diversion facility.

Project outflow -- The volume of water per unit of time released from a project.

Public Utility -- A private business organization, subject to government regulation, that provides an essential commodity or service, such as water, electricity, transportation, or communications, to the public.

Public utility district (PUD) -- A government unit established by voters of a district to supply electric or other utility service.

Reregulating project -- A dam and reservoir, located downstream from a hydroelectric peaking plant, with sufficient storage capacity to store the widely fluctuating discharges from the peaking plant and to release them in a relatively uniform manner downstream.

Reregulation -- Storing erratic discharges of water from an upstream hydroelectric plant and releasing them uniformly from a downstream plant.

Reservoir -- A body of water collected and stored in an artificial lake behind a dam.

Rockfill Dam -- An embankment dam in which more than 50 percent of the total volume is comprised of compacted or dumped pervious natural or crushed rock.

Rolled Fill Dam -- An embankment dam of earth or rock in which the material is placed in layers and compacted by using rollers or rolling equipment.

Rule curves -- Water levels, represented graphically as curves, that guide reservoir operations.

Run-of-river dams -- Hydroelectric generating plants that operate based only on available inflow and a limited amount of short-term storage (daily/weekly pondage).

Shaping -- The scheduling and operation of generating resources to meet seasonal and hourly load variations.

Sluiceway -- An open channel inside a dam designed to collect and divert ice and trash in the river (e.g., logs) before they get into the turbine units and cause damage. (On several of the Columbia River dams, ice and trash sluiceways are being used as, or converted into, fish bypass systems.)

Spill -- Releasing water through the spillway rather than through the turbine units.

Spillway -- "The channel or passageway around or over a dam through which excess water is released or "spilled" past the dam without going through the turbines. A spillway is a safety valve for a dam and, as such, must be capable of discharging major floods without damaging the dam, while maintaining the reservoir level below some predetermined maximum level."

Spillway crest elevation -- The point at which the reservoir behind a dam is level with the top of the dam's spillway.

Storage -- The volume of water in a reservoir at a given time.

Storage reservoir -- A reservoir in which storage is help over from the annual high water period to the following low water period.

Subimpoundment -- An isolated body of water created by a dike within a reservoir or lake.

Submersible traveling screen -- A wire mesh screen that acts like a conveyor belt when installed in the intakes of turbines at dams guiding and transporting juvenile fish into bypass channels.

Supersaturation -- See dissolved gas concentrations.

Tailrace -- The canal or channel that carries water away from the dam.

Tailwater -- The water surface immediately downstream from a dam or hydroelectric powerplant.

Trap and haul program -- A program to collect fish at a given point, transport them to a different point, and release them.

Turbine -- A mechanism in a dam that rotates with the force of water and produces electricity.

Turbine intake screens -- Large screens, which may have moving or non moving parts, designed to be placed in a dam's turbine intake at an angle to deflect juvenile fish from the intakes into a bypass system.

Uncontracted water -- A volume of water in a storage reservoir that is not assigned for other purposes, such as irrigation.

Velocity barrier -- A physical structure, such as a barrier dam or floating weir, built in the tailrace of a hydroelectric powerhouse, which blocks the tailrace from further adult salmon or steelhead migration to prevent physical injury or migration delay.

Wasteway -- An open ditch or canal that discharges excess irrigation water or power plant effluent into the river channel.

Water banking -- An administrative system for renting surplus water.

Water budget -- A provision of the Columbia River Basin Fish and Wildlife Program that calls for increasing Columbia and Snake River Flows during the spring fish migration with the intent of increasing downstream survival of migrating juvenile salmon and steelhead.

Water rights -- "Priority claims to water. In western States, water rights are based on the principle "first in time, first in right," meaning older claims take precedence over newer ones."

Watt -- A measure of the rate at which energy is produced, exchanged, or consumed.

Weir (dam) -- A dam in a river to stop and raise the water, for the purpose of conducting it to a mill, forming a fishpond, or the like. When uncontrolled, the weir is termed a fixed-crest weir. Other types of weirs include broad-crested, sharp-crested, drowned, and submerged.