Water terms starting with T

133 terms

Tagout The placement of a tagout device on an energy isolating device, in accordance with an established procedure, to indicate that the energy isolating device…
Tagout device A prominent warning device, such as a tag and a means of attachment, which can be securely fastened to an energy isolating device in accordance with an…
Tailings Second grade or waste material separated from pay material during screening or processing.
Tailings dam. See mine tailings dam.
Tailrace. See afterbay.
Tailwater The water in the natural stream immediately downstream from a dam. The elevation of water varies with discharge from the reservoir.
Tailwater Height Height of water immediately downstream of the dam. (Various datums may be used.)
Tainter gate A term used by the Corps of Engineers to describe radial gates (see gate).
Talus Rock debris accumulated at the base of the cliff or slope from which they have broken off.
Tamp To pound or press soil to compact. To firmly compact earth during backfilling.
Tamper A tool for compacting soil in spots not accessible to rollers.
Tamping A method of compacting soil using the impact of a power or hand tamper on the surface of the soil placed.
Tamping roller One or more steel drums, fitted with projection feet, used to densify soil. See sheepsfoot roller.
Tandem A pair in which one part follows the other.
Tangent A line that touches a circle and is perpendicular to its radius at the point of contact.
Taproot A big root that grows downward from the base of a tree.
Tectonics The science that deals with the structure of the earth's crust.
Tee A pipe fitting that has two threaded openings in line, and a third at right angles to them.
Telescope To slide one piece inside another.
Temporary irrigation service land Irrigable land for which a water supply is delivered under temporary arrangements. The acreage may vary from year to year.
Temporary structure Any structure that can be readily and completely dismantled and removed from the site between periods of actual use.
Tensiometer Instrument, consisting of a porous cup filled with water and connected to a manometer or vacuum gauge, used for measuring the soilwater matrix potential.
Terminal structure Portion of spillway downstream from chute, tunnel or conduit, which generally dissipates or stills releases.
Terrace A step-like surface, bordering a valley floor or shoreline, that represents the former position of a floodplain, lake, or sea shore.
Terrain Topographic layout and features of a tract of land or ground.
Terrestrial Things of the land.
Territorial communities Populations that function within a particular geographic area.
Test pit Pit dug for geologic investigation or inspection and testing of earthwork placement.
Thalweg Deepest part of a river channel in a cross section of a river profile. The path of deepest flow. Line connecting the deepest points along a riverbed.
Theodolite An instrument used in surveying to measure horizontal and vertical angles with a small telescope that can move in the horizontal and vertical planes.
Theory most logical explanation of an event that occurs in nature.
Thermal sand Sand used to dissipate heat away from buried electrical cables.
Thermal stratification The formation of layers of different temperatures in bodies of water. See stratification.
Thermal-electric powerplant A generating plant which uses heat to create steam driven electricity. Such plants may burn coal, gas, oil, wood, waste; or use nuclear, solar, and…
Thermocline A distinct layer of water where rising warm and sinking cold water meet but do not mix.
Thermocouple A device consisting of two dissimilar conductors with their ends connected together.
Thick arch dam An arch dam with a base thickness to structural height ratio of 0.3 or greater (previously defined as 0.5 or greater).
Thickness or width of dam The thickness or width of a dam as measured horizontally between the upstream and downstream faces and normal to the axis or centerline crest of the dam.
Thin arch dam An arch dam with a base thickness to structural height ratio of 0.2 or less (previously defined as 0.3 or less).
Thixotrophy The property of a material that enables it to stiffen in a relatively short time on standing but, upon agitation or manipulation, to change to a very soft…
Threatened A legal classification for a species which is likely to become endangered within the foreseeable future.
Threatened species Any species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.
Threshold Runoff The runoff in inches from a rain of specified duration that causes a small stream to slightly exceed bankfull.
Through cut An excavation between parallel banks that begins and ends at original grade.
Thrust block (anchor block) A massive block of concrete built to withstand a thrust or pull. A mass of concrete or similar material appropriately placed around a pipe to prevent…
TIDE The periodic, rhythmic rise and fall of the sea surface that results from the gravity of the moon and sun acting on the rotating Earth.
Tidelands The zone between the mean high water and mean low water lines.
Tie lines Transmission line connecting two or more power systems.
Tier 1 Reclamation public protection guideline dealing with loss of life (LOL) considerations. See annualized loss of life.
Tier 2 Reclamation public protection guideline dealing with public trust responsibilities based on the annual failure probability of the structure.
Tiering The coverage of general matters in a broad National Environmental Policy Act document with subsequent narrowly focused documents; helps to eliminate…
Tight This is an undesirable condition of the race car. A NASCAR race car is tight when the front wheels loose grip before the rear wheels loose grip when going…
Tile Pipe made of baked clay.
Till A deposit of sediment formed under a glacier, consisting of an unlayered mixture of clay, silt, sand, and gravel ranging widely in size and shape.
Tillage Plowing, seedbed preparation, and cultivation practices. See conventional tillage.
Tilth Soil condition in relation to lump or particle size.
Timber Wood beams larger than 4 x 6.
Timbering Wood bracing in a tunnel or excavation.
Timbering set A tunnel support consisting of a roof beam or arch, and two posts.
Time of concentration The time required for storm runoff to flow from the most remote point of a catchment or drainage area to the outlet or point under consideration.
Tipping-Bucket Rain Gage A precipitation gage where collected water is funneled into a two compartment bucket; 0.01, 0.
Toe (toe of dam) The point of intersection between the bottom of a slope or the upstream or downstream face of a dam and the natural ground, for example, the upstream or…
Toe Drain (or Outfall) A drain which carries seepage away from the dam and can allow seepage quantities to be measured.
Toe drain(s) Open-jointed tile or perforated pipe located at the toe of the dam used in conjunction with horizontal drainage blankets to collect seepage from the…
Toe of Dam The junction of the downstream face with the ground surface. See also, "Heel of Dam".
Toe of Dam (Upstream and Downstream) The junction of the face of a dam with the ground surface.
Toe weight Additional material placed at the toe of an embankment dam to increase its stability.
Top of active conservation capacity The reservoir water surface elevation at the top of the capacity allocated to the storage of water for conservation purposes only. See reservoir.
Top of Dam See crest elevation.
Top of dead capacity The lowest elevation in the reservoir from which water can be drawn by gravity.
Top of exclusive flood control capacity The reservoir water surface elevation at the top of the reservoir capacity allocated to exclusive use for the regulation of flood inflows to reduce damage…
Top of inactive capacity The reservoir water surface elevation below which the reservoir will not be evacuated under normal conditions.
Top of joint use capacity The reservoir water surface elevation at the top of the reservoir capacity allocated to joint use, i.e., flood control and conservation purposes.
Top of surcharge capacity The maximum water surface of a reservoir.
Top Thickness See "Crest Width".
Top width or thickness The thickness or width of a dam at the level of the top of dam (excluding corbels or parapets).
Topographic map A map indicating surface elevation and slope. U.S. Geological Survey quadrangle series maps showing the shape of the earth's surface by contours.
Topography The shape of the Earth's surface; the relative position and elevations of natural and human-made features of an area.
Topsoil The topmost layer of soil, usually containing organic matter. Usually refers to soil containing humus which is capable of supporting plant growth.
Total capacity The reservoir capacity below the highest of the elevations representing either the top of exclusive flood control capacity, the top of joint use capacity…
Total dissolved solids (TDS) The dry weight of dissolved material, organic and inorganic, contained in water. The term is used to reflect salinity.
Total dynamic head (TDH) When a pump is lifting or pumping water, the vertical distance from the elevation of the energy grade line on the suction side of the pump to the…
Total Gross Reservoir Capacity The total amount of storage capacity available in a reservoir for all purposes from the streambed to the normal water or normal water or normal pool…
Total maximum daily loads (TMDL) Estimates of the amount of specific pollutants that a body of water can safely take without threatening beneficial uses.
Totalizer (integrator) A device or meter that continuously measures and calculates (adds) total flow.
toxin (TOK-sin) A poison produced by certain animals, plants, or bacteria.
Trace A hydrograph or similar plot for an extended-range time horizon showing one of many scenarios generated through an ensemble forecast process.
Trace (of Precipitation) A rainfall amount less than 0.01 of an inch.
Tractor gate Rectangular gate supported and sealed similar to the paradox gate. Main difference is that the leaf is raised and lowered by a cable hoist, and operated…
Traditional cultural property (TCP) A site or resource that is eligible for inclusion in the National Register of Historic Places because of its association with cultural practices or…
Traffic control point A location staffed to ensure the continued movement of traffic inside or outside an area of risk during an emergency or disaster.
Training wall A wall built to confine or guide the flow of water.
Tranquil flow Distinguished from rapid flow by a dimensionless number called the Froude number. If the Froude number is less than one, the flow is tranquil.
transducer A device that converts electrical energy to sound energy, or the reverse. Typically associated with depth finders or fish finders.
Transfer point. See turning point.
Transferred works Facilities owned by Reclamation, but operated and maintained by an irrigation district or other entity.
Transformed flow net A flow net whose boundaries have been properly modified (transformed) so that a net consisting of curvilinear squares can be constructed to represent flow…
Transformer An electromagnetic device that changes the voltage of alternating current electricity.
Transit A surveying instrument that can measure both vertical and horizontal angles.
Transition zone (semipervious zone) A substantial part of the cross section of an embankment dam comprising material whose grading is of intermediate size between that of an impervious zone…