Water terms starting with H

125 terms

Habitat The natural environment where people, animals and plants live. In an aquatic environment, it includes the water, topography, structure and cover present…
Habitat Areas of Particular Concern (HAPC) A habitat area designated by a Fishery Management Council under the Magnuson-Stevens Fishery Conservation and Management Act of 1976 to help focus…
Halophytic Salt-loving. Plants that thrive in soils that contain salt and/or sodium. A plant that grows in salty or alkaline soil.
Hanger A support for pipe.
Hanging (ice) dam A mass of ice composed mainly of frazil or broken ice deposited underneath an ice cover in a region of low flow velocity.
Hard water Water may be considered hard if it has a hardness greater than the typical hardness of water from the region.
Hardness A characteristic of water determined by the levels of calcium and magnesium. Water hardness is largely the result of geological formations of the water…
Hardpan A dense, often impermeable soil horizon cemented with silica, iron oxides, calcium carbonate, or organic matter.
Harrow An agricultural tool that loosens and works the ground surface.
Harvest In a recreational fishery, refers to numbers of fish that are caught and kept. See catch.
Hatchery A facility where fish and raised for stocking.
Haul distance The distance measured along the center line or most direct practical route between the center of the mass of excavation and the center of mass of the fill…
Haunches (haunch) The outside areas between the springline and the bottom of a pipe. In pipe, the sides of the lower third of the circumference.
Hazard Something (e.g., a dam) that creates the potential for adverse consequences such as loss of life (LOL), property damage, and adverse social and…
Hazard classification The rating for a dam based on the potential consequences of failure. The rating is based on potential for loss of life and damage to property that failure…
Hazardous materials Materials that pose the potential for grave, immediate, future, and genetic injury and illness when handled without proper equipment and precautions.
Hazardous substances Element or compound other than oil which when discharged into the environment, in any quantity, presents an imminent or substantial threat to public…
Hazardous Waste Indicators Indicators that may signal the presence of hazardous materials include stressed vegetation or unusual lack of vegetation; dead or sick domestic stock…
Hazardous waste sites Any spill, authorized or unauthorized dumping, abandoned, or inactive waste disposal sites containing or suspected of containing hazardous materials.
HDRAIN An Hourly Digital Rainfall Product of the WSR-88D.
Head The upper horizontal part of a window frame or window opening.
Head Loss The energy lost from a flowing fluid due to friction, transitions, bends, etc.
Head Race A channel which directs water to a water wheel; a forebay.
Header A masonry wall unit of brick which is laid so that its short end is exposed.
Heading In a tunnel, a digging face and its work area.
Headrace. See forebay.
Headwall An upstream wall.
Headward Erosion Erosion which occurs in the upstream end of the valley of a stream, causing it to lengthen its course in such a direction.
Headwater (1) The source and upper reaches of a stream; also the upper reaches of a reservoir; (2) the water upstream from a structure or point on a stream; (3) the…
Headwater Advisory Program (ADVIS) A Program which uses the Antecedent Precipitation Index (API) method of estimating runoff, unit hydrograph theory and stage-discharge ratings to produce…
Headwater Advisory Table A table developed by a River Forecast Center for a Headwater Guidance Point; a pre-computed matrix of values allows a forecaster to ascertain an…
Headwater Basin A basin at the headwaters of a river. All discharge of the river at this point is developed within the basin.
Headwaters Streams at the source of a river.
Heap The soil carried above the sides of a body or bucket.
Heave The upward movement of land surfaces or structures due to subsurface expansion of soil or rock, or vertical faulting of rock.
Hectare An area equal to 2.47 acres. There are 100 hectares in 1 square kilometer.
Heel of Dam The junction of the upstream face of a concrete gravity dam or arch dam with the ground surface.
Height of dam. See hydraulic height or structural height.
Helical Spiral.
Herbicide A chemical that kills plants.
Herbivore Animal that feeds on plants.
Herpetofauna Amphibian and reptile species including frogs, toads, salamanders, turtles, lizards, and snakes.
Hertz (Hz) The unit of measurement of frequency, equivalent to one cycle per second.
High dam A dam over 300 feet high. See low dam and medium-height dam.
High hazard A downstream hazard classification for dams in which more than 6 lives would be in jeopardy and excessive economic loss (urban area including extensive…
High-pressure gate A gate consisting of a rectangular leaf encased in a body and bonnet and equipped with a hydraulic hoist for moving the gate leaf.
Hinge Crack Crack caused by significant changes in water level.
HOE A shovel that digs by pulling a broom-and-stick-mounted bucket toward itself.
Hogback Ridge formed by erosion of resistant, steeply inclined sedimentary layers.
Hoist The mechanism by which a bucket or blade is lifted, or the process of lifting it.
Hollow gravity dam (cellular gravity dam) A dam which has the outward appearance of a gravity dam but is of hollow construction.
Hollow-jet valve A valve having a closing member that moves upstream to shut off the flow. The hollow-jet valve discharges a hollow or annular jet dispersed over a wide…
Homogeneous earthfill dam An embankment dam construction throughout of more or less uniform earth materials, except for possible inclusion of internal drains or blanket drains.
Homogeneous Rolled Earth Dam An embankment dam constructed of similar earth material throughout, except for possible inclusion of internal drains or drainage blankets; distinguished…
Hopper A storage bin or a funnel that is loaded from the top, and discharges through a door or chute in the bottom.
Hornblende Black blade-like mineral common in igneous and metamorphic rocks.
Hornfels Fine-grained, gray-green metamorphic rock produced by "baking" of sedimentary rocks by an igneous intrusion in which sedimentary features may still be…
Horsehead (false set) A temporary support for forepoles used in tunneling soft ground.
Horsepower (hp) A unit of rate of operation. Electrical hp: a measure of time rate of mechanical energy output; usually applied to electric motors as the maximum output…
Horst An elongated crustal block that is relatively raised between two parallel normal faults or grabens. See also Half-graben
Howell Bunger valve. See fixed cone valve.
Hub A network device that connects multiple computers/peripherals together and allows them to share data.
Human environment Natural and physical environment and the relationship of people with that environment, including all combinations of physical, biological, cultural…
Hummock A hillock of broken ice which has been forced upward by pressure.
Hummocked Ice Ice piled haphazardly one piece over another to form an uneven surface.
Humus Decayed organic matter. A dark fluffy swamp soil composed chiefly of decayed vegetation.
Hydraucone A draft tube in which the emerging water impinges on a plate.
Hydraulic Powered by water. Having to do with water in motion.
Hydraulic efficiency Efficiency of a pump or turbine to impart energy to or extract energy from water.
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 Grade Line A line whose plotted ordinate position represents the sum of pressure head plus elevation head for the various positions along a given fluid flow path…
Hydraulic grade line (HGL) (Hydraulic gradient) The hydraulic grade line lies below the energy grade line by an amount equal to the velocity head at the section.
Hydraulic Head (1) The height of the free surface of a body of water above a given point beneath the surface.
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…
Hydraulic Mean Depth The right cross-sectional area of a stream of water divided by the length of that part of its periphery in contact with its containing conduit; the ratio…
Hydraulic Permeability The flow of water through a unit cross-sectional area of soil normal to the direction of flow when the hydraulic gradient is unity.
Hydraulic Radius The right cross-sectional area of a stream of water divided by the length of that part of its periphery in contact with its containing conduit; the ratio…
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. A power plant that produces electricity from the power of rushing water turning…
Hydroelectric power The generation of electricity using falling water.
Hydroelectric unit (hydrounit) An electric generator and turbine combination which is driven by water flow, thereby converting mechanical energy to electric energy.
Hydrogeochemistry Chemistry of ground water and surface water.
Hydrogeologic conditions Conditions stemming from the interaction of ground water and the surrounding soil and rock.
Hydrogeologic cycle The natural process of recycling water from the atmosphere down to (and through) the earth and back to the atmosphere again.
Hydrogeologist A person who studies and works with ground water.
Hydrogeology The geology of ground water, with particular emphasis on the chemistry and movement of water.
Hydrograph A graphical representation of the stage or discharge as a function of time at a particular point on a watercourse; a time-discharge curve of the unsteady…
Hydrograph Separation The process where the storm hydrograph is separated into baseflow components and surface runoff components.
Hydrographic Survey An instrumental survey to measure and determine characteristics of streams and other bodies of water within an area, including such things as location…
Hydrography Scientific study of physical aspects of all waters on the Earth's surface. Water features in 7.
Hydrologic Budget An accounting of the inflow to, outflow from, and storage in, a hydrologic unit, such as a drainage basin, aquifer, soil zone, lake, reservoir, or…
Hydrologic Cycle Cycle of water movement from atmosphere to Earth by precipitation and its return to the atmosphere by interception, evaporation, runoff, infiltration…
Hydrologic Equation The water inventory equation (Inflow = Outflow + Change in Storage) which expresses the basic principle that during a given time interval the total inflow…
Hydrologic Model A conceptual or physically-based procedure for numerically simulating a process or processes which occur in a watershed.
Hydrologic Operations Division (HOD) The Hydrologic Operations Division of the Office of Hydrology (OH).
Hydrologic Service Area (HSA) A geographical area assigned to Weather Service Forecast Office's/Weather Forecast Office's that embraces one or more rivers.
Hydrologic Services A general term referring to the operations, products, verbal communications, and related forms of support provided by the NWS for the Nation's streams…