Glossary

acre-foot
The amount of water it takes to cover one acre to a depth of one foot, 43,560 cubic feet or 1,233.5 cubic meters

active storage
The volume of water in a reservoir between its minimum operating elevation and its maximum normal operating elevation.
alluvium
Material such as sand, silt or clay, deposited on land by water such as on floodplains.

anadromous fish
Fish that live in saltwater habitats most of their lives, but periodically migrate into freshwater to spawn and develop to the juvenile stage (e.g., alewife).

aquatic life
Any plants or animals which live at least part of their life cycle in water.

baseline
A set of existing environmental conditions upon which comparisons are made during the NEPA process.

base load
A power plant that is planned to run continually except for maintenance and scheduled or unscheduled outages. Also refers to the nearly steady level of demand on a utility system.

benthic
Associated with lake or river bottom or substrate.

benthic macroinvertebrates
Animals without backbones, which are visible to the eye and which live on, under, and around rocks and sediment on the bottoms of lakes, rivers, and streams.

capacity
The load for which an electric generating unit, other electrical equipment or power line is rated.

catadromous fish
Fish that live in freshwater most of their lives, but periodically migrate to the sea to spawn (e.g., American eel).

Clean Water Act (CWA)
The Federal Water Pollution Control Act of 1972 and subsequent amendments in 1977, 1981, and 1987 (commonly referred to as the Clean Water Act). The Act established a regulatory system for navigable waters in the United States, whether on public or private land. The Act set national policy to eliminate discharge of water pollutants into navigable waters, to regulate discharge of toxic pollutants, and to prohibit discharge of pollutants from point source without permits. Most importantly it authorized EPA to set water quality criteria for states to use to establish water quality standards.

colluvium
Soil material and/or rock fragments moved by gravity such as during creep, slide, or localized wash-outs, which is deposited at the base of steep slopes.

combustion turbine
A fuel-fired turbine engine used to drive an electric generator.

conservation
A process or program designed to increase the efficiency of energy and water use, production, or distribution.

creel census
Counting and interviewing anglers to determine fishing effort and catch. Usually conducted by a census clerk on systematic regularly scheduled visits to significant fishing areas.

cubic feet per second (cfs)
A measurement of water flow representing one cubic foot of water moving past a given point in one second. One cfs is equal to 0.0283 cubic meters per second and 0.646 mgd.

cultural resources
Includes items, structures, etc. of historical, archaeological, or architectural significance.

cumulative impact
The effect on the environment that results from the incremental impact of the action when added to other past, present, and reasonably foreseen future actions. Can result from individually minor but collectively significant actions taking place over a period of time.

dam
A structure constructed across a water body typically used to increase the hydraulic head at hydroelectric generating units. A dam typically reduces the velocity of water in a particular river segment and increases the depth of water by forming an impoundment behind the dam. It also generally serves as a water control structure.

demand
The rate at which electric energy is delivered to or by a system at a given instant or averaged over a designated period, usually expressed in kilowatts or megawatts.

development
one of several hydroelectric plants collectively licensed by the Federal Energy Regulatory Commission as a Project. (Example: The Coosa River Project consists of 5 developments - Weiss, Henry, Logan Martin, Lay, and Bouldin)

dike
A raised bank, typically earthen, constructed along a waterway to impound the water and to prevent flooding.

dissolved oxygen (DO)
A water quality parameter describing the amount of oxygen present.

distribution lines
Power lines, like those in neighborhoods, used to carry moderate voltage electricity which is "stepped down" to household levels by transformers on power poles.

drawdown
The distance the water surface of a reservoir is lowered from a given elevation as the result of releasing water.

emergent aquatic vegetation
Plants rooted in substrate covered by shallow water (of up to 6.6 ft depth), with most of the parts out of the water.

energy
Average power production over a stated interval of time, expressed in kilowatt-hours, megawatt-hours, average kilowatts and average megawatts.

eutrophic
Waters with a high concentration of nutrients and a high level of primary production.

evapotranspiration
The evaporation from all water, soil, snow, ice, vegetation, and other surfaces, plus transpiration.

Federal Energy Regulatory Commission
The governing federal agency responsible for overseeing the licensing/relicensing and operation of hydroelectric projects in the United States.

Federal Power Act (FPA)
Federal statute enacted in 1920 that established the Federal Power Commission (now FERC) and the statutes for licensing hydroelectric projects.

Federal Power Commission (FPC)
Predecessor of FERC

Federal Register
A publication of the Federal Government that includes official transactions of the U.S. Congress, as well as all federal agencies such as FERC. Copies of the Federal Register are usually available at large public and university libraries.

flow
The volume of water passing a given point per unit time.

flow duration curve
A graphical representation of the percentage of time in the historical record that a flow of any given magnitude has been equaled or exceeded.

forebay
That portion of a hydroelectric project impoundment immediately upstream of the intake to the turbines (see also headwaters).

generation
The process of producing electricity from other forms of energy, such as steam, heat, or water. Refers to the amount of electric energy produced, expressed in kilowatt hours.

gross storage
The sum of the dead storage and the live storage volumes of a reservoir, the total amount of water contained in a reservoir at its maximum normal operating elevation.

habitat
The locality or external environment in which a plant or animal normally lives and grows.

head
The distance that water falls in passing through a hydraulic structure or device such as a hydroelectric plant. Gross head is the difference between the headwater and tailwater levels; net head is the gross head minus hydraulic losses such as friction incurred as water passes through the structure; and rated head is the head at which the full-gate discharge of a turbine will produce the rated capacity of the connected generator.

headwater
The waters immediately upstream of a dam. For power dams, also referred to as the water in the impoundment which supplies the turbines (see also forebay).

hydraulic
Relating to water in motion.

hydroelectric plant
A facility at which the turbine generators are driven by falling water.

hydroelectric power
Capturing flowing water to produce electrical energy.

hydroelectric project
The complete development of a hydroelectric power site, including dams, reservoirs, transmission lines, and accessories needed for the maintenance and operation of the powerhouse and any other hydroelectric plant support facilities.

hypolimnetic
The deeper cooler portions of a reservoir or lake that result from stratification.

impoundment
The body of water created by a dam.

Induced surcharge curve
a set of lake level elevations used to manage flows during periods of high inflow to ensure protection of downstream lands from flooding.

Initial Stage Consultation Document (ISCD)
A document containing detailed information on a hydroelectric project; the document is used to describe the project and its resources and to start the applicant's consultation process with resource agencies and the public.

kilowatt (kW)
A unit of electrical power equal to 1,000 watts.

kilowatt-hour (kWh)
A basic unit of electricity consumption equals to 1 kW of power used for one hour. A kilowatt-hour equals the amount of electricity needed to burn ten, 100-watt light bulbs for one hour.

lacustrine
Related to standing water, (e.g., a lake).

lentic
Standing or still water including lakes, ponds, and swamps.

license
FERC authorization to construct a new project or continue operating and existing project. The license contains the operating conditions for a term of 30 to 50 years.

littoral
Associated with shallow (shoreline area) water (e.g., the littoral zone of an impoundment).

load
The total customer demand for electric service at any given time.

lotic
Flowing or actively moving water including rivers and streams.

mainstem
The main channel of a river as opposed to the streams and smaller rivers that feed into it.

maximum drawdown elevation
The lowest surface elevation to which a reservoir can be lowered and still maintain generation capability. This is usually somewhat lower than the minimum operating elevation.

maximum normal operating elevation
The maximum surface elevation to which the reservoir can be raised without surcharging or exceeding the license provisions.

megawatt (MW)
A unit of electrical power equal to one million watts or 1,000 kW.

megawatt-hour (MWh)
A unit of electrical energy equal to 1 MW of power used for one hour.

minimum normal operating elevation
The lowest elevation to which a reservoir is normally lowered during power generation operations. Below this point power output and generation efficiency is significantly impacted.

nameplate capacity (also called installed capacity)
A measurement indicating the approximate generating capability of a project or unit, as designated by the manufacturer. In many cases, the unit is capable of generating substantially more than the nameplate capacity since most generators installed in newer hydroelectric plants have a continuous overload capacity of 115 percent of the nameplate capacity.

National Environmental Policy Act (NEPA)
A law passed by the U.S. Congress in 1969 to establish methods and standards for review of development projects requiring Federal action such as permitting or licensing.

Non-Governmental Organizations (NGOs)
Local, regional and national organizations such as conservation, sportman's or commerce groups.

normal operating elevation
The reservoir elevation approximating an average surface elevation at which a reservoir is kept.

normal operating elevation range
The elevation difference between the normal maximum and normal minimum operating elevations.

off peak
A period of relatively low demand for electrical energy, such as the middle of the night.

on peak
A period of relatively high demand for electrical energy.

outage
The period during which a generating unit, transmission line, or other facility is out of service.

palustrine emergent wetland
Contains rooted herbaceous vegetation that extend above the water surface (i.e., cattails, sedges)

palustrine forested wetland
Dominated by woody vegetation less than 20 ft tall (i.e., willows, dogwood)

palustrine scrub/shrub wetlands
Comprised of woody vegetation that is 20 ft tall or greater (i.e., American elm, swamp white oak).

peaking operations
A powerplant that is scheduled to operate during peak energy demand.

periphyton
Macroscopic (visible without a microscope) and microscopic (visible only with a microscope) algae (single- and multi-celled plants) that grow on or attach to rocks, logs, and aquatic plants. Periphyton, phytoplankton, and aquatic plants are the primary producers that convert nutrients into plant material by the process of photosynthesis.

phytoplankton
Algae floating in the water column. These are mostly microscopic single-celled and colonial forms.

ponding operations
The process of storing and releasing water based on electric demand or flood control.

peak demand
A one hour period in a year representing the highest point of customer consumption of electricity.

piezometer
A device that measures water pressure.

pool
Refers to the reservoir (impounded body of water).

powerhouse
The building that typically houses electric generating equipment.

power pool
A regional organization of electric companies interconnected for the sharing of reserve generating capacity.

Probable Maximum Flood (PMF)
A statistical formula used to calculate a hypothetical flood event that could occur on a particular river basin over a particular duration. This is derived from the probable maximum precipitation over time.

project
one or more hydroelectric plants collectively included in a single Federal Energy Regulatory Commission license. Projects typically consist of a dam, reservoir, powerhouse and appurtenant facilities.

project area
APC lands and waters within the project boundary.

project boundary
A line established by the FERC to enclose the lands, waters and structures needed to operate a licensed hydroelectric project.

project vicinity
Lands and waters within which studies were conducted for baseline environmental data. These lands and waters include the Project area.

public utility
A business enterprise rendering a service considered essential to the public and, as such, subject to regulation.

ramp rate
The rate of change in output from a power plant. A maximum ramp rate is sometimes established to prevent undesirable effects due to rapid changes in loading or, in the case of hydroelectric plants, discharge.

relicensing
The administrative proceeding in which FERC, in consultation with other federal and state agencies, decide whether and on what terms to issue a new license for an existing hydroelectric project at the expiration of the original license.

reserve capacity
Extra generating capacity available to meet unanticipated demand for power or to generate power in the event of loss of generation.

reservoir
An artificial lake into which water flows and is stored for future use.

resident fish
Fish that spend their entire life cycle in freshwater, such as trout and bass.

resource agency
A federal, state, or interstate agency with responsibilities in the areas of flood control, navigation, irrigation, recreation, fish or wildlife, water resource management, or cultural or other relevant resources of the state in which a project is or will be located.

rhizome
Underground stem.

riparian area
A specialized form of wetland with characteristic vegetation restricted to areas along, adjacent to or contiguous with rivers and streams. Also, periodically flooded lake and reservoir shore areas, as well as lakes with stable water.

river miles
Miles from the mouth of a river; for upstream tributaries, from the confluence with the main river.

run
A general term referring to upriver migration of anadromous fish over a particular time and area - often composed of multiple individual breeding stocks.

run-of-river
A term used to describe the operation of a hydroelectric project in which the quantity of water discharged from the project essentially equals the flow in the river.

runner
The rotating part of a turbine.

Scoping Document 1 (SD1)
A document prepared by FERC as part of NEPA environmental review that initially identifies issues pertinent to FERC's review of a project. FERC circulates the SD1 and holds a public meeting to obtain the public's comment.

Scoping Document 2 (SD2)
A revision to SD1 which takes into account public comment on that document.

scoping process
T he process of identifying issues, potential impacts, and reasonable alternatives associated with the operation of a hydroelectric project. "Scoping" is a process required by any federal agency taking an action that might affect the quality of the human environment, pursuant to the National Environmental Policy Act (NEPA) of 1969. In the case of hydro projects, FERC's issuance of an operating license qualifies as a federal action.

secchi depth
Average depth at which a standard size black and white disk disappears and reappears when viewed from the lake surface as it is lowered. An indicator of water clarity.

seepage
The amount of water that leaks through a structure, such as a dam.

spawn
The act of fish releasing and fertilizing eggs.

spillway
The section of a dam that is designed to pass water over or through it.

stakeholder
any individual or organization (government or non-governmental) with an interest in a hydroelectric project

stock
The existing density of a particular species of fish in an aquatic system.

stratification
A physical and chemical process that results in the formation of distinct layers of water within a lake or reservoir (i.e., epilimnion, metalimnion, and hypolimnion).

streamflow
The rate at which water passes a given point in a stream, usually expressed in cubic feet per second (cfs).

submerged aquatic vegetation
Plants with rigid stems and/or leaves rooted in substrate and generally covered by deep water (greater than 6.6 ft depth), with all of the plant parts covered by water.

tailrace
The channel located between a hydroelectric powerhouse and the river into which the water is discharged after passing through the turbines.

tailwater
The waters immediately downstream of a dam. For power dams, also referred to as the water discharged from the draft tubes.

tainter gate
A gate with a curved skin or face plate connected with steel arms to an axle. It is usually lifted or lowered by a cable connected to a hook at the top of the gate rotating on the axle as it is moved.

taxon
A means of referring to a set of animals or plants of related classification, such as all of the species (i.e., brook trout, lake trout) in a genus (trout); or all of the genera (all trout and salmon) in a family of fishes (salmonidae). Plural form of taxon is taxa.

transformer
Equipment vital to the transmission and distribution of electricity designed to increase or decrease voltage.

transmission
The act or process of transporting electric energy in bulk from one point to another in the power system, rather than to individual customers.

transmission lines
Power lines normally used to carry high voltage electricity to substations which then is "stepped down" for distribution to individual customers.

transpiration
The process by which water absorbed by plants is converted to vapor and discharged to the atmosphere.

turbidity
A measure of the extent to which light passing through water is reduced due to suspended materials.

turbine
A machine for generating rotary mechanical power from the energy in a stream of fluid (such as water, steam, or hot gas). Turbines covert the energy of fluids to mechanical energy through the principles of impulse and reaction, or a mixture of the two.

vantage point
The location from which a viewer sees the landscape.

volt
The unit of electromotive force or electric pressure, akin to water pressure in pounds per square inch.

warmwater fish
Species tolerant of warm water (e.g., bass, perch, pickerel, sucker).

watershed
An entire drainage basin including all living and nonliving components of the system.

wetlands
Lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. Wetlands must have the following three attributes: 1) at least periodically, the land supports predominantly hydrophytes; 2) the substrate is predominantly undrained hydric soil; 3) the substrate is on soil and is saturated with water or covered by shallow water at some time during the growing season of each year.

zooplankton
Microscopic and macroscopic animals that swim in the water column. These invertebrates include chiefly three groups: rotifers, cladocerans, and copepods.