Water — page 29 of 31

Water terms

2801. 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…
2802. Thermocline A distinct layer of water where rising warm and sinking cold water meet but do not mix.
2803. Thermocouple A device consisting of two dissimilar conductors with their ends connected together.
2804. 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).
2805. 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.
2806. 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).
2807. 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…
2808. Threatened A legal classification for a species which is likely to become endangered within the foreseeable future.
2809. 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.
2810. Threshold Runoff The runoff in inches from a rain of specified duration that causes a small stream to slightly exceed bankfull.
2811. Through cut An excavation between parallel banks that begins and ends at original grade.
2812. 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…
2813. 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.
2814. Tidelands The zone between the mean high water and mean low water lines.
2815. Tie lines Transmission line connecting two or more power systems.
2816. Tier 1 Reclamation public protection guideline dealing with loss of life (LOL) considerations. See annualized loss of life.
2817. Tier 2 Reclamation public protection guideline dealing with public trust responsibilities based on the annual failure probability of the structure.
2818. Tiering The coverage of general matters in a broad National Environmental Policy Act document with subsequent narrowly focused documents; helps to eliminate…
2819. 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…
2820. Tile Pipe made of baked clay.
2821. 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.
2822. Tillage Plowing, seedbed preparation, and cultivation practices. See conventional tillage.
2823. Tilth Soil condition in relation to lump or particle size.
2824. Timber Wood beams larger than 4 x 6.
2825. Timbering Wood bracing in a tunnel or excavation.
2826. Timbering set A tunnel support consisting of a roof beam or arch, and two posts.
2827. 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.
2828. Tipping-Bucket Rain Gage A precipitation gage where collected water is funneled into a two compartment bucket; 0.01, 0.
2829. 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…
2830. Toe Drain (or Outfall) A drain which carries seepage away from the dam and can allow seepage quantities to be measured.
2831. 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…
2832. Toe of Dam The junction of the downstream face with the ground surface. See also, "Heel of Dam".
2833. Toe of Dam (Upstream and Downstream) The junction of the face of a dam with the ground surface.
2834. Toe weight Additional material placed at the toe of an embankment dam to increase its stability.
2835. 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.
2836. Top of Dam See crest elevation.
2837. Top of dead capacity The lowest elevation in the reservoir from which water can be drawn by gravity.
2838. 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…
2839. Top of inactive capacity The reservoir water surface elevation below which the reservoir will not be evacuated under normal conditions.
2840. 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.
2841. Top of surcharge capacity The maximum water surface of a reservoir.
2842. Top Thickness See "Crest Width".
2843. Top width or thickness The thickness or width of a dam at the level of the top of dam (excluding corbels or parapets).
2844. 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.
2845. Topography The shape of the Earth's surface; the relative position and elevations of natural and human-made features of an area.
2846. Topsoil The topmost layer of soil, usually containing organic matter. Usually refers to soil containing humus which is capable of supporting plant growth.
2847. 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…
2848. Total dissolved solids (TDS) (TDS) The dry weight of dissolved material, organic and inorganic, contained in water. The term is used to reflect salinity.
2849. 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…
2850. 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…
2851. Total maximum daily loads (TMDL) Estimates of the amount of specific pollutants that a body of water can safely take without threatening beneficial uses.
2852. Totalizer (integrator) A device or meter that continuously measures and calculates (adds) total flow.
2853. toxin (TOK-sin) A poison produced by certain animals, plants, or bacteria.
2854. Trace A hydrograph or similar plot for an extended-range time horizon showing one of many scenarios generated through an ensemble forecast process.
2855. Trace (of Precipitation) A rainfall amount less than 0.01 of an inch.
2856. 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…
2857. 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…
2858. 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.
2859. Training wall A wall built to confine or guide the flow of water.
2860. 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.
2861. transducer A device that converts electrical energy to sound energy, or the reverse. Typically associated with depth finders or fish finders.
2862. Transfer point. See turning point.
2863. Transferred works Facilities owned by Reclamation, but operated and maintained by an irrigation district or other entity.
2864. 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…
2865. Transformer An electromagnetic device that changes the voltage of alternating current electricity.
2866. Transit A surveying instrument that can measure both vertical and horizontal angles.
2867. 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…
2868. Transmission To cause spread of germs.
2869. Transmission line A set of electrical current conductors, insulators, supporting structures, and associated equipment used to move large quantities of power at high…
2870. Transmissivity The rate at which water of the prevailing kinematic viscosity is transmitted through a unit width of the aquifer under a unit hydraulic gradient.
2871. Transpiration The process by which water in plants is transferred into water vapor in the atmosphere. Evaporation of water through the leaves of plants.
2872. Transport capacity The capacity of a river to carry sediment in suspension or to move sediment along the riverbed. Usually expressed as mass per unit of time.
2873. Transverse Pertaining to or extending along the short axis, or width, of a structure. Perpendicular to or across the long axis, or length, of a structure.
2874. Trapezoidal weir. See Cipolletti weir.
2875. Trash Rack A screen located at an intake to prevent the ingress of debris.
2876. Trash rake A device that is used to remove debris which has collected on a trashrack to prevent blocking the associated intake.
2877. Trashrack A metal or reinforced concrete structure placed at the intake of a conduit, pipe, or tunnel that prevents entrance of debris over a certain size.
2878. Trashrake A device that is used to remove debris which has collected on a trashrack to prevent blocking the associated intake.
2879. Travel Time Time measured from the start of a dam breach to flooding at a particular location.
2880. Tremie A device used to place concrete or grout under water.
2881. Trench(es). See ditch.
2882. Trestle A bridge, usually of timber or steel, that has a number of closely spaced supports between the abutments.
2883. Triaxial shear test A test in which a specimen of soil or rock encased by an impervious membrane is subjected to a confining pressure and then loaded axially to failure.
2884. Tribe Term used to designate a federally recognized group of American Indians and their governing body. Tribes may be composed of more than one band.
2885. Tributary A creek, stream, or river that feeds a larger stream or river, or lake.
2886. Tripod A three-legged support for a surveying instrument.
2887. Trophic level Place of an animal in the food chain.
2888. Trunnion A heavy horizontal hinge.
2889. Tube valve A valve which is opened or closed by mechanically moving a tube upstream or downstream by an actuating screw.
2890. Tuff Volcanic rock made up of rock and mineral fragments in volcanic ash matrix. Tuffs commonly are composed of much shattered volcanic rock glass—chilled…
2891. Tunnel Covered portion of spillway between the gate or crest structure and the terminal structure, where open channel flow and/or pressure flow conditions may…
2892. Turbid Having a cloudy or muddy appearance.
2893. Turbidimeter A device that measures the amount of suspended solids in a liquid.
2894. Turbidity The relative clarity of water, which may be affected by material in suspension in the water.
2895. Turbine A device for converting the flow of a fluid (air, steam, water, or hot gases) into mechanical motion.
2896. Turbulent flow That type of flow in which any water particle may move in any direction with respect to any other particle, and in which the head loss is approximately…
2897. Turn angles To measure the angle between directions with a surveying instrument.
2898. Turning Point A temporary point whose elevation is determined by additions and subtractions of backsights and foresights respectively.
2899. Turning point (transfer point) A point whose elevation is taken from two or more instrument positions to determine their height in relation to each other.
2900. Turnout A structure used to divert water from a supply channel to a smaller channel.