NPDP Dam Dictionary

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Term AKA Definition
Hydraucone A draft tube in which the emerging water impinges on a plate.
Hydraulic fill Fill material that is transported and deposited using water.
Hydraulic fill dam An embankment dam constructed of materials, often dredged, which are conveyed and/or placed by suspension in flowing water.
Hydraulic fill structure A dam or impoundment made of hydraulic fill.
Hydraulic gradient The slope of the surface of open or underground water.
Hydraulic Height Height to which the water rises behind the dam, and is the difference between the lowest point in the original streambed at the axis or the centerline crest of the dam and the maximum controllable water surface. See structural height.
Hydraulics Having to do with the mechanical properties of water in motion and the application of these properties in engineering
Hydric Characterized by, or thriving in, an abundance of moisture.
Hydroelectric plant Electric powerplant using falling water as its motive force.
Hydroelectric power Electrical energy produced by flowing water.
Hydrogeochemistry Chemistry of ground and surface water.
Hydrograph A graph showing for a given point on a stream, river, or conduit, the discharge, stage, velocity, available power, or other property of water with respect to time.
Hydrography Scientific study of physical aspects of all waters on the Earth's surface
Hydrologic cycle Cycle of water movement from atmosphere to Earth by precipitation and its return to the atmosphere by interception, evaporation, runoff, infiltration, percolation, storage, and transpiration.
Hydrology Scientific study of water in nature: its properties, distribution, and behavior. The science that treats the occurrence, circulation properties, and distribution of the waters of the earth and their reaction to the environment.
Hydrometeorological Report HMR A series of hydrometeorological reports published by the National Weather Service addressing meteorological issues related mainly to developing estimates of probable maximum precipitation used in the determination of the probable maximum flood for design of water control structures.
Hydrometer A device for measuring the specific gravity of fluids.
Hydrostatic Relating to pressure or equilibrium of fluids.
Hyperconcentrated flow Moving mixture of sediment and water between 40 and 80 percent water by volume.
Hypolimnetic Pertaining to the lower, colder portion of a lake or reservoir which is separated from the upper, warmer portion (epilimnion) by the thermocline.
Hypolimnion The lower layer of a lake or reservoir with essentially uniform colder temperatures. See stratification.
Ichthyology The scientific study of fish.
Igneous Rock formed by molten magma.
Impeller A rotary pump member using centrifugal force to discharge a fluid into outlet passages
Impervious Not permeable; not allowing liquid to pass through.
Impervious core See core.
Impervious material Relatively waterproof soils. Clay, for example, since water will percolate through clay at about one millionth of the rate at which it will pass through gravel.
Impervious zone See core.
Impinge To collide or strike.
Impoundment Body of water created by a dam.