NPDP Dam Dictionary

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Term AKA Definition
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.
Gigawatt gw Unit of power equal to 1 billion watts.
Gigawatthour GWh One billion watthours of electrical energy.
Gradation Proportion of material of each grain-size present in a given soil
Grade The elevation of a surface or a surface slope.
Grade stake A stake indicating the amount of cut or fill required to bring the ground to a specified level.
Graded stream Streams that receive and carry away equal amounts of sediment.
Grader A machine with a centrally located blade that can be angled to cast to either side, with independent hoist control on each side.
Gradient General slope or rate of change in vertical elevation per unit of horizontal distance of water surface of a flowing stream. Slope along a specific route, as of a road surface, channel or pipe.
Grapple A clamshell-type bucket having three or more jaws.
Gravel Loose rounded fragments of rock that will pass a 3-inch sieve and be retained on a No. 4 sieve (3/16 inch).