Thin arch damAn arch dam with a base thickness to structural height ratio of 0.2 or less (previously defined as 0.3 or less).
Thin filmA layer of semiconductor material, such as copper indium diselenide or gallium arsenide, a few microns or less in thickness, used to make solar…
Thin Line EchoA narrow, elongated, non-precipitating echo. It is usually associated with thunderstorm outflows, fronts, or other density discontinuities.
thinning1. Removal of older stems to promote new growth. 2. Removal of excess fruits to improve the size and quality of the remaining fruits. 3.
ThixotrophyThe 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…
Thorn forestA type of forest formation, mostly tropical and subtropical, intermediate between desert and steppe, dominated by small trees and shrubs.
ThreatenedA legal classification for a species which is likely to become endangered within the foreseeable future.
Threatened speciesAny species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.
Three-Hour Rainfall RateThis WSR-88D Radar product displays precipitation total (in inches) of the current and past two clock hours as a graphical image.
Three-phase CurrentAlternating current in which three separate pulses are present, identical in frequency and voltage, but separated 120 degrees in phase.
Thresholdthe point a system must cross to enter a new state or condition.
Threshold RunoffThe runoff in inches from a rain of specified duration that causes a small stream to slightly exceed bankfull.
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…
thymidylic acid(Abbreviation: TMP or dTMP). Synonym for thymidine 5'-monophosphate, a deoxyribonucleotide containing the nucleoside thymidine.
thymine(Abbreviation: T). One the bases found in DNA. See: thymidine.
Thymine (T)A nitrogenous base, one member of the base pair AT (adenine-thymine). See also: base pair, nucleotide
ThymusAn organ that is part of the lymphatic system, in which T lymphocytes grow and multiply. The thymus is in the chest behind the breastbone.
Ti (tumor-inducing) plasmidA giant plasmid of Agrobac- terium tumefaciens that is responsible for tumor formation in infected plants.
Ti plasmidTumour-inducing plasmid. A large plasmid present in pathogenic Agrobacterium tumefaciens, responsible for the induction of tumours in plant with crown…
Tidal CycleThe periodic changes in the intensity of tides caused primarily by the varying relations between the earth, moon, and sun.
Tidal PilingOccurs when unusually high water levels occur as the result of an accumulation of successive incoming tides that do not completely drain due to opposing…
Tidal PowerThe power available from the rise and fall of ocean tides. A tidal power plant works on the principal of a dam or barrage that captures water in a basin…
TIDEThe periodic, rhythmic rise and fall of the sea surface that results from the gravity of the moon and sun acting on the rotating Earth.
Tide AnomalyActual water level minus the prediction.
Tide PredictionThe computation of tidal highs and lows at a given location resulting from the gravitational interactions between the earth and primarily the moon and sun.
TidelandsThe zone between the mean high water and mean low water lines.
TidesThe periodic (occurring at regular intervals) variations in the surface water level of the oceans, bays, gulfs, and inlets.
Tie linesTransmission line connecting two or more power systems.
Tier 1Reclamation public protection guideline dealing with loss of life (LOL) considerations. See annualized loss of life.
Tier 2Reclamation public protection guideline dealing with public trust responsibilities based on the annual failure probability of the structure.
TieringThe coverage of general matters in a broad National Environmental Policy Act document with subsequent narrowly focused documents; helps to eliminate…
TightThis 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…
TillA deposit of sediment formed under a glacier, consisting of an unlayered mixture of clay, silt, sand, and gravel ranging widely in size and shape.
TillagePlowing, seedbed preparation, and cultivation practices. See conventional tillage.
TiltTo play wildly or recklessly. A player is said to be "on tilt" if he is not playing his best, playing too many hands, trying wild bluffs, raising with bad…
Timber stand improvementIntermediate pruning, weeding, and thinning of a stand of timber prior to its reaching mature rotation age to improve growing conditions and control stand…
Timbering setA tunnel support consisting of a roof beam or arch, and two posts.
TimberlandForest land capable of producing 20 cubic feet of wood per acre per year.
Time of concentrationThe 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.
Time-of-Use (TOU) RatesThe pricing of electricity based on the estimated cost of electricity during a particular time block.
Time-of-use pricingA rate design imposing higher charges to customers during periods of the day when higher demand is experienced.
TimerA device that can be set to automatically turn appliances (lights) off and on at set times.
Timer (Water Heater)This device can automatically turn the heater off at night and on in the morning.
Tip Speed RatioIn reference to a wind energy conversion device's blades, the difference between the rotational speed of the tip of the blade and the actual velocity of…
Tipping-Bucket Rain GageA precipitation gage where collected water is funneled into a two compartment bucket; 0.01, 0.
Tissue(TISH-oo) A group or layer of cells that work together to perform a specific function.
Tissue cultureThe in vitro culture of cell s, tissue s or organ s in a nutrient medium under sterile conditions.
titre1. The concentration of infectious virus particles present in a suspension. 2. A measure of antibody concentration, given by the highest dilution of the…
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 DamThe junction of the downstream face with the ground surface. See also, "Heel of Dam".
Toe weightAdditional material placed at the toe of an embankment dam to increase its stability.
ToleranceA condition in which higher doses of a drug are required to produce the same effect achieved during initial use; often associated with physical dependence.
Tolerance inductionThe "education" process that T cells undergo to discriminate between self and foreign proteins. This process takes place primarily in the thymus.
Tolling agreementAn agreement whereby a party moves fuel to a power generator and receives kilowatt hours (kWh) in return for pre-established fees.
tonoplastThe cytoplasmic membrane bordering the vacuole of plant cells. It plays a prominent role in regulating the osmotic pressure exerted by the cell sap.
Top of active conservation capacityThe reservoir water surface elevation at the top of the capacity allocated to the storage of water for conservation purposes only. See reservoir.
Top of dead capacityThe lowest elevation in the reservoir from which water can be drawn by gravity.
Top of exclusive flood control capacityThe 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 capacityThe reservoir water surface elevation below which the reservoir will not be evacuated under normal conditions.
Top of joint use capacityThe reservoir water surface elevation at the top of the reservoir capacity allocated to joint use, i.e., flood control and conservation purposes.