NPDP Dam Dictionary

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Term AKA Definition
Frost line The greatest depth to which ground may be expected to freeze.
Froude number The ratio of inertial forces to gravitational forces in flow. It is also the ratio of the flow velocity to the velocity of a small gravity wave in the flow. When the Froude number is less than one, the flow is tranquil. When the Froude number is greater than one, the flow is rapid. When the Froude number is equal to one, the flow is critical.
Fry Life stage of fish between the egg and fingerling stages. Depending on the species of fish, fry can measure from a few millimeters to a few centimeters.
Fuel replacement energy Electric energy generated at a hydroelectric plant as a substitute for energy which would have been generated by a thermal electric plant.
Fulcrum A pivot for a lever.
Full hydraulic capacity The designed capacity of a pipe or conduit.
Full pool Volume of water in a reservoir at normal water surface.
Furrow A natural or man-made narrow depression in the earth's surface. A narrow trenchlike plowed depression in the earth surface to keep surface water away from the slopes of cuts.
Fuse A thin core of black powder surrounded by wrappings, which when lit at one end, will burn to the other at a fixed speed. A string-like core of PETN, a high explosive, contained within a waterproof reinforced sheath. Primacord" is the best known brand."
Future without What would occur if no action were taken. See baseline condition.
Gabion Wire basket, filled with stones, used to stabilize banks of a water course and to enhance habitat.
Gabion dam Special name given to a crib dam when built with gabions. See dam.
Gaining stream Stream or reach that receives water from the zone of saturation.
Gallery A passageway within the body of a dam, its foundation, or abutments.
Gametes Eggs or sperm.
Gantry An overhead structure that surrports machines or operating parts, such as a gantry crane
Gaseous supersaturation Condition of higher levels of dissolved gases in water due to entrainment, pressure increases, or heating.
Gate A device that controls the flow in a conduit, pipe, or tunnel without obstructing any portion of the waterway when in the fully open position. See cylinder gate, drum gate, fixed- wheel gate, guard gate, high-pressure gate, jet-flow gate, radial gate, regulating gate, ring gate, ring- follower gate, roller gate, slide gate, or tainter gate.
Gate chamber A chamber in which a guard gate in a pressurized outlet works or both the guard and regulating gates in a free-flow outlet works is located. Concrete portion of an outlet works containing gates between upstream and downstream conduits and/or tunnels.
Gate hanger A device used to maintain a set gate opening.
Gate structure Portion of spillway between inlet channel and chute, tunnel or conduit, which contains gates, such as radial gates.
Gate valve A valve with a circular-shaped closing element that fit securely over an opening through which water flows.
Gauge Gauging station Specific location on a stream where systematic observations of hydrologic data are obtained through mechanical or electrical means. Thickness of wire or sheet metal.
Generation The energy generated in kWh (kilowatt-hours) represents gross generation. It consists of the total generation minus station use. Process of producing electric energy by transforming other forms of energy.
Generator Machine that converts mechanical energy into electrical energy.
Geohydrology Geological study of the character, source, and mode of groundwater.
Geology The science that deals with the physical history of the earth, the rocks of which it is comprised, and the physical changes which the earth has undergone or is undergoing.
Geomorphic Of or relating to the form or shape of the earth.
Geomorphology Geological study of the configuration, characteristics, origin, and evolution of land forms and earth features.
Geophysics Refers to the physics of the earth, e.g., seismology, oceanography, volcanology, geomagnetism, etc.