Terms of Hydrology (T)

tailrace :

Channel which conducts water away from a water-wheel or turbine.

tailwater :

Water located just downstream from a hydraulic structure on a str ...

telemetering :

Recording at a distance of indications from instruments.

temperature lapse rate :

Decrease of the air temperature in degrees Celsius per 100 m of a ...

tensiometer :

Instrument that consists essentially of a porous cup inserted in ...

thalweg :

Line following the deepest part of a streambed or channel or of a ...

thaw :

Melting of snow and ice at the earth's surface, following a tempe ...

thermal infrared :

Preferred term for the middle wavelength ranges of the infrared r ...

thermal load :

(1) Amount of heat transported by a river or canal per unit of ti ...

thermal spring :

Spring, the temperature of which is above the mean annual tempera ...

thermocline :

Layer in thermally stratified body of water in which the temperat ...

thermo-mineral spring :

Thermal spring of a high mineral content.

thermo-osmosis :

Flow through porous media caused by differences of temperature.

Thiessen polygon :

Polygons formed by the perpendicular bisectors of the straight li ...

thixotropic :

Description of a substance that acts like a gel when stationary b ...

throat :

Minimum cross-sectional area within a flume. It may have any shap ...

throughfall :

Part of rainfall that reaches the ground directly through the veg ...

tidal piezometric efficiency :

Ratio of the range of the fluctuations of the piezometric level i ...

tidal prism :

Volume of water that flows with the movement of the tide into a t ...

tidal range :

Difference in height between high tide and a consecutive low tide ...

tidal river :

River in which the flow and water-level are affected by tides.

tide :

Periodic rise and fall of water in the seas or in large lakes due ...

time of concentration :

Period of time required for storm runoff to flow to the outlet fr ...

time series :

Set of observations, in order, taken at successive points of time ...

toe of interface :

Line of intersection between the bottom of an estuary or a coasta ...

tolerance :

Permissible variation of the specified value of a quantity. (TR)

tolerance limit :

Limiting lower or upper value specified for a quantitative charac ...

torrent :

Watercourse having a steep slope, flowing in general with great v ...

tortuosity :

(1) Ratio of the actual length of a stream channel measured betwe ...

total acidity :

Amount of both weak and strong acids in water, usually expressed ...

total dissolved solids (tds) :

Total weight of dissolved mineral constituents in water per unit ...

total head :

Sum of the elevation of the free surface of a stream above a hori ...

total storage :

Volume of a reservoir including dead storage below the maximum co ...

trace element :

Chemical element present in a minor amount in water.

tracer :

Easily detectable material which may be added in small quantities ...

tractive force :

Force parallel to the bed exerted by flowing water on a sediment ...

translatory wave :

Gravity wave that propagates in an open channel in a direction pa ...

transmissivity :

Rate at which water is transferred through a unit width of an aqu ...

transpiration :

Process by which water from vegetation is transferred into the at ...

trap efficiency :

Ability of a reservoir to trap and retain sediment, expressed as ...

travel time :

Time elapsing between the passage of a water parcel or packet bet ...

trend :

Long-term smooth movement in a time series.

triangular-profile weir :

Long-base weir having a longitudinal triangular profile. (ISO/772 ...

tributary :

Watercourse flowing into a larger watercourse or into a lake.

tritium unit (T.U.) :

Unit used to express tritium concentrations. One tritium unit is ...

tropical cyclone :

Cyclone of tropical origin of small diameter (some hundreds of ki ...

true value :

Value which characterizes a quantity in the conditions which exis ...

tsunami :

Great sea wave produced by a submarine earthquake or volcanic eru ...

Turbidity :

Condition of a liquid due to fine, visible material in suspension ...

turbulent flow :

Flow with turbulence. In channel flow, it occurs at Reynolds numb ...

Turnover :

(1) Action of turning over of a water body, e.g. a lake, whether ...

turnover rate :

Ratio of the annual average groundwater recharge, expressed in vo ...

turnover time :

Time required for supplying a volume equal to the total water res ...

twin-gauge station; twin-gage station (A) :

Gauging station at which two water level gauges define a reach fo ...