| Acre-foot (AF) |
The volume of water require to over one acre to a depth of one foot. 1 acre-foot= 43,560 cubic feet or 326,000 gallons. |
| Capacity |
The load for which a generator, turbine, transformer, transmission circuit, apparatus, station or system is rated. Capacity is also used synonymously with capacity. |
| Circuit Breaker |
Any switching device that is capable of closing or interrupting an electrical circuit. |
| Confluence |
The combining of two streams. |
| Conservation Pool |
Usable storage in reservoir for hydropower, recreation, water quality, fish and wildlife management, navigation, and water supply purposes, designed to be filled during normal and high flow periods for use during low flow periods. |
Cubic Feet per
Second (cfs) |
1cfs=450 gallons per minute (gpm) |
| Demand |
The rate of water flow through, over, or around water control facilities. The rate of flow is measured by stream gage or calculated from predetermined rating tables. The term may be applied to the rate of flow from each individual source (such as a particular turbine) or to be algebraic summation from all individual sources (which would be the total rate of flow). Total discharge is synonymous with outflow. |
| Discharge |
The rate of water flow through, over, or around water control facilities. The rate of flow is measured by stream gage or calculated from predetermined rating tables. The term may be applied to the rate of flow from each individual source (such as a particular turbine) or to be algebraic summation from all individual sources (which would be the total rate of flow). Total discharge is synonymous with outflow. |
| Drawdown |
The distance that the water surface elevation of a storage reservoir is lowered from a given or starting elevation as a result of the withdrawal of water to meet some project purpose(s) such as power generation or creating flood control space. |
Drought Contingency
Plan |
Detailed drought management plan that addresses current water conditions in the Savannah River Basin, and serves as a baseline for future |
| Drought Indicators |
Mechanisms which reflect drought conditions and severity. Drought indicators consist of hydrologic indicators such as streamflow, rainfall, reservoir storage levels and groundwater levels, meteorological indicators such as rainfall, and human activity indicators, which include navigation cutbacks and reduction in hydropower generation.
|
| Drought Response |
A response network consists of trigger levels and appropriate management action. Triggers are predetermined standards reflecting drought intensity which induce responses.
|
| Effluent |
Waste material discharges into the environment. |
| Flood Control Pool |
Storage above the conservation pool elevation designed to store floodwater and reduce flooding downstream.
|
| Flow |
The amount of water passing a given point within a given period of time. |
| Forebay |
The impoundment immediately above a dam or hydroelectric plant intake structure. The term is applicable to all types of hydroelectric developments (e.g. storage, run-of-river, and pumped-storage).
|
| Generating Unit |
A single power producing unit, comprised of a turbine, generator, and related equipment.
|
| Generation |
The act or process of producing electricity from other forms of energy. Also, the amount of electric energy so produced.
|
| Generator |
The electrical equipment in power systems that converts mechanical energy to electrical energy.
|
| Governor |
The device which measures and regulates turbine speed by controlling wicket gate angle to adjust water flow to the turbine.
|
| Guide Curve |
(also Rule Curve or Target Pool Levels). Guides established to regulate and manage optimum pool elevations for yearly operations at impoundments. Rule curves can be designed to regulate storage for flood control, hydropower production, and other operating objectives, as well as a combination of objectives.
|
| Hydroelectric Plant |
An electric power plant that uses water to generate power.
|
| Hydropower Power |
The energy that is produced from water.
|
| Impoundment |
A confined body of water such as a reservoir or lake. Typically created by a dam to store water that is released to meet to maintain authorized purposes |
| Inflow |
The rate of water flow into a reservoir or forebay during a specified period.
|
| Kilowatt (kW) |
The electric unit of power, which equals 1,000 watts or 1.341 horsepower.
|
| Kilowatt hour (kWh) |
Unit for measuring electric energy consumption or generation over time; it equals one kilowatt of power applied for one hour of time. A typical home uses about 800 kilowatt hours per month.
|
| Load |
The amount of electric power consumed/delivered at a given point. |
| Megawatt(mW) |
Unit of electric power, used for measuring rate of producing or consuming electric energy. One megawatt = 1,000 kilowatts or 1 million watts. A megawatt is equal to 1,341 horsepower.
|
Meteorological
Conditions |
Atmospheric phenomena and weather of a region. |
| Minimum Discharge |
The minimum flow that must be released from a project to meet environmental or other non-power requirements.
|
| Minimum Pool Level |
The lowest elevation to which the pool is to be drawn. |
| Multi-Purpose Reservoir |
A reservoir planned to be used for more than one purpose. |
| Normal Pool Level |
The elevation to which the reservoir surface will rise during ordinary conditions.
|
| Outage |
The period during which a generating unit, transmission line, or other facility is out of service.
|
| Peak Demand Month |
The month or months of highest power demand. |
| Peaking Plant |
A powerplant which is normally operated to provide power during maximum load periods.
|
| Penstock |
A conduit carries water from the reservoir to the turbine in a hydroelectric plant.
|
| pH |
The condition represented by a number, used to express both acidity and alkalinity on a scale whose values run from 0 to 14 with 7 representing neutrality, numbers less than 7 increasing acidity.
|
| Powerplant |
A generating station where prime movers (such as turbines), electric generators, and auxiliary equipment for producing electricity are located. |
| Pumped storage |
A hydropower facility that has reservoir pumps which also serve as generators, installed in the dam. During the night, when cheap surplus power is available, the pumps are run to pump water from a lower reservoir to an upper reservoir (upstream). During mid-day, when valuable peaking power is needed, the units are reversed and water is released back to the lower reservoir to generate electricity.
|
| Releases |
A determined amount of water that is allowed to pass through or discharged from a dam.
|
| Reregulation Structure |
Peaking power plants generally release water only a few hours per day. A reregulation structure is a smaller dam located downstream that is capable of storing the intermittent slugs of water and releasing a continuous flow.
|
| Rule Curve |
Same as “Guide Curve.”
|
| Streamflow |
The rate at which water passes a given point in a stream, usually expressed in cubic feet per second.
|
| Switchyard |
An assemblage of electrical equipment for the purpose of tying together two or more electric circuits through switches, selectively arranged in order to permit a circuit to be disconnected or to change the electric connection between the circuits. In a hydroelectric project, the switchyard is the point at which the energy generated at the project is connected to the distribution system.
|
| Tailrace |
The area below a dam; the channel that carries water away from a dam.
|
| Thermally Stratify |
During the warm months of the year, the sun heats the upper layers of the lake. Since the warm water rises, the surface of the lake continues to warm while the bottom layer stays cold. During the winter months, the upper layers of the lake are cooled. The warmer water on the bottom rises, causing destratification, or “turnover”, of the lake.
|
| Transformer |
An electromagnetic device used to change the electricity from the generator to usable voltage levels.
|
| Transmission Line |
The high voltage lines that carry electricity from the hydropower plant to the electric distribution system.
|
| Triggering Mechanism |
An indicator that is put in place to indicate the need to initiate or terminate specific action before a crisis occurs. At the action levels, the trigger elevation will initiate a series of actions that will culminate in the reduction of releases from the projects.
|
| Turbine |
Large blades that are turned by the force of water pushing against it; is connected to the generator.
|
| Voltage |
The force which causes the current to flow through an electrical conductor. |
| Watt |
Basic unit of electrical power that is produced at one time or rate of doing work. The rate of energy transfer equivalent to one ampere flowing under a pressure of one volt at unity power factor. One horsepower is equivalent to approximately 746 watts. |
| Wheeling |
The transfer of power and energy from one utility over the transmission system of a second utility for delivery to a third utility, or to a load of the first utility. |
| Wicket Gates |
Adjustable vanes that control the amount of water that can enter the turbine.
|
|
ABBREVIATIONS
|
| AF |
acre-feet |
| cfs |
cubic feet per second
|
| cu |
cubic
|
| ft |
foot, feet |
| gal |
gallons |
| gph |
gallons per hour |
| gpm |
gallons per minute |
| km |
kilometer |
| kv |
kilovolt |
| kva |
kilovolt-amperes |
| kWh |
kilowatts per hour |
| m |
meter |
| mgd |
million gallons per day |
| mi |
mile |
| MWH |
Megawatts per hour |
| MSA |
Metropolitan Statistical Area |
| NGVD |
National Geodetic Vertical Datum |
| rpm |
revolutions per minute |
| SAD |
South Atlantic Division |
| SEPA |
Southeast Power Administration |
| sq |
square |
| WES |
Waterways Experiment Station |
| / |
per |
|
CONVERSION FACTORS
|
|
Length
1 mi = 5,280 ft = 1.609 km
1 km = 0.6214 mi = 3,281 ft
Area
1 sq mi = 640 acres = 2.590 sq km
1 acre = 43,560 sq ft = 4,047 sq m
Volume
1 AF = 325,872 gal = 1,233 cu m
1 AF = 43,560 cu ft = 1,613 cu yd
1 cfs-day = 1.983 AF
1 cubic foot = 7.48 gallons = 0.0283 cubic meters
1 cfs-day = 1.983 AF
1 cubic meter = 35.51 cubic feet
Discharge Rate
1 cu m/sec = 15,850 gpm = 70.04 acre-ft/day
1 cfs = 2,228 gpm = 0.646317 mgd = 1.983 AF/day
1 AF/day = 226.3 gpm = 0.5042 cfs
1 gpm = 8.0208 cu ft/hr
1 cubic foot per second (cfs) =
448.83 gallons per minute (gpm)
0.646 million gallons per day (mgd)
0.0283 cubic meters per second (cms)
Energy
1 kilowatt –hour (kWh) = 3,413 BTU [i]
1 kilowatt (kW) = 1,000 watts
= 1.341 horsepower
= 56.88 BTU/minute
= 737.56 ft-lbs/second
1 megawatt (MW) = 1,000 kilowatts
= 1 million watts
1 gigawatt (gW) = 1,000 megawatts
Energy Equivalents
1 barrel of oil (42 gallons) = 470 kWh at 27% efficiency [i]
= 520 kWh at 30 % efficiency
= 660 kWh at 38% efficiency [iii]
1 ton of coal = 2,500 kWh at 37% efficiency [iv]
1,000 cubic feet of natural gas =
59 kWh at 27% efficiency [ii]
83 kWh at 38% efficiency [iii]
[i] 1 BTU (British Thermal Unit) is the amount of energy required to raise the temperature of one pound of water one degree Fahrenheit.
[ii] Typical efficiency for a combustion turbine.
[iii] Typical efficiency for new oil- or gas-fired base load steam plant or combined cycle plant.
[iv] Typical efficiency for a new base load coal-fired steam plant.
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