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T

TACKING—The binding of Mulch fibers by mixing them with an adhesive chemical compound during land Restoration projects.

TAHOE-PROSSER EXCHANGE AGREEMENT—Also referred to as the "Agreement for Water Exchange Operations of Lake Tahoe and Prosser Creek Reservoir," this agreement was finalized in June 1959 and designated certain waters in Prosser Reservoir in the Truckee River Basin as "Tahoe Exchange Water." By this agreement, when waters were to be released from Lake Tahoe for a minimum instream flow (50 cfs winter; 70 cfs summer) and when such releases from Lake Tahoe were not necessary for Floriston Rates due to normal flows elsewhere in the river, then an equal amount of water (exchange water) could be stored in Prosser Reservoir and used for releases at other times. Also see Truckee River Agreement [Nevada and California].

TAIGA—A subarctic, evergreen coniferous forest of northern Eurasia located just south of the Tundra and dominated by firs and spruces. Also referred to as a Boreal Forest. Also see Biome.

TAILINGS—The waste material remaining after metal is extracted from ore.

TAILRACE—(1) The part of a Millrace below the water wheel through which the spent water flows; the channel which conducts water away from a water wheel. (2) A channel for floating away mine tailings and refuse. (3) A race for conveying water away from a point of industrial application (as a waterwheel or turbine) after use.

TAIL WATER—(1) In Hydraulics, water, in a river or channel, immediately downstream from a structure. (2) In Irrigation, water that reaches the lower end of a field; excess surface water draining especially from a field under cultivation. Tail water is not necessarily lost; it can be collected and reused on the same or adjacent fields.

TAILWATER RECOVERY—The process of collecting irrigation water runoff for reuse in the system.

TAILWATER RUNOFF—Refers to unused irrigation water or rain water that is collected at the base or at the end of an irrigation system or field in a ditch or other impoundment. This water may be reused again for irrigation purposes, left to evaporate, percolate into the ground, treated, and/or discharged to surface bodies of water.

TANK—An artificial pool, pond, reservoir, cistern, or large container for holding and storing water for drinking or irrigation.

TAP—A valve and spout used to regulate delivery of a fluid at the end of a pipe.

TAPERED AERATION—A modification of the activated sludge process wherein air is introduced at a higher rate at the head of the tank than in subsequent sections.

TAP WATER—Water withdrawn directly from a tap or faucet.

TAR BALLS—Non-volatile hydrocarbon clumps remaining in water after the volatile fractions have evaporated from crude oil that has been discharged or spilled into the marine environment. When washed ashore, these residues, which range in size from marbles to beach balls, spoil beaches and marine habitat.

TARN—A small steep-banked mountain lake or pool, generally formed by a glaciation process.

TAXONOMY—The science, laws, or principles of classifying living organisms in specially named categories based on shared characteristics and natural relationships.

TCID—See Truckee-Carson Irrigation District (TCID).

TDS (TOTAL DISSOLVED SOLIDS)—All the solids (usually mineral salts) that are dissolved in water. Used to evaluate water quality.

TECHNOLOGY-BASED—Describing emission or effluent limitations that are not defined in terms of allowable releases that achieve a desirably low ambient pollutant concentration, but instead are based on the pollutant control efficiency that is achievable using current levels of technology.

TECHNOLOGY-BASED LIMITATIONS—(EPA) Industry-specific effluent limitations applied to a discharge when it will not cause a violation of water quality standards at low stream flows. Usually applied to discharges into large rivers.

TECHNOLOGY-BASED STANDARDS—(EPA) Effluent limitations applicable to direct and indirect sources which are developed on a category-by-category basis using statutory factors, not including water-quality effects.

TECHNOLOGY-FORCING—Describing standards or levels of pollution and effluent control called for in environmental statutes or regulations for which existing technologies are inadequate and therefore require technical advancements to achieve.

TELECONNECTION—(Meteorology) A term which describes the influence of an aberration in weather patterns in one part of the world to cause strange weather in another area of the globe. Also see El Niño, El Niño/Southern Oscillation (ENSO), and Hurricane Forecasting.

TEMPERATE (DECIDUOUS) FOREST—Forested areas characterized by moderate temperatures, weather, or climate, and rainfall from 30 to 60 inches per year. These forests are found in eastern North America, eastern Australia, western, central, and eastern Europe, and parts of China and Japan. Typical deciduous trees in the North American deciduous forests are oak, hickory, maple, ash, and beech. Also see Biome.

TEMPERATURE—The degree of hotness or coldness. Also, a measure of the average energy of the molecular motion in a body or substance at a certain point.

TEMPERATURE GRADIENT—The rate of change of temperature with increase in height or decrease in depth.

TEMPERATURE INVERSION—A surface cooling at the earth's surface which sometimes leads to an increase in temperature with altitude.

TEMPERATURE REGULATION—The processes through which an organism's temperature is adjusted to certain metabolic requirements or conditions in its environment. For example, the act of human perspiration promotes surface skin evaporation which cools the body.

TEMPERATURE SCALE—The temperature scale adopted by a 1960 international conference was based on a fixed temperature point, the Triple Point of water, at which the solid, liquid, and gas are in equilibrium. The temperature of 273.16 K (Kelvin) was assigned to this point. The freezing point of water was designated as 273.15 K, equaling exactly 0 on the Celsius Temperature Scale. The Celsius scale, which is identical to the Centigrade Temperature Scale, is named for the 18th-century Swedish astronomer Anders Celsius, who first proposed the use of a scale in which the interval between the freezing and boiling points of water is divided into 100 degrees. By international agreement, the term Celsius has officially replaced Centigrade.

TEMPEST—A violent windstorm, frequently accompanied by rain, snow, or hail.

TEMPORARY HARDNESS—Water hardness that can be reduced or removed by heating the water. Heating drives off carbon dioxide, shifting the carbonate buffer system equilibrium so that carbonate ions combine with dissolved calcium or magnesium ions, form solids, and precipitate. This lowers the calcium/magnesium ion water concentration, lowering the hardness. Also referred to as Carbonate Hardness. Also see Ion Exchange.

TEMPORARY WETLAND—A type of Wetland in which water is present for only part of the year, usually during the wet or rainy seasons (e.g., spring). Also referred to as Vernal Pools.

TENAJA—Pools in seasonal streams that may support a flora similar to Vernal Pools upon desicca