751 articles
Thermal regime
A thermal regime, in stream ecology, is the characteristic pattern of water temperature in a river or stream through time, described by magnitude, variability, frequency, duration, and timing of temperatures.
Thermocline
The thermocline, also called the metalimnion in lakes, is the water layer where temperature drops fastest with depth, separating warm surface water from the deep ocean.
Thermohaline circulation
Thermohaline circulation, also called the global conveyor belt, is the global system of deep-ocean currents driven by density differences from temperature and salinity, turning over all deep water roughly every 600 years.
Thermosalinograph
A thermosalinograph (TSG) is a shipboard instrument that continuously measures sea surface temperature and salinity along a ship's track, using seawater drawn through a pumped intake while the vessel is underway.
Throughfall
Throughfall is the portion of precipitation that reaches the ground beneath a vegetation canopy, passing through gaps or dripping and splashing from leaves, branches, and stems.
Throughflow
Throughflow, also called interflow or subsurface stormflow, is the lateral movement of water through soil above a less permeable layer during storms, dominating steep catchments and contributing to streamflow.
Tidal asymmetry
Tidal asymmetry is the inequality between the flood and ebb phases of a tidal cycle, arising when tidal waves distort in shallow water and shaping estuary sediment transport.
Tidal bore
A tidal bore, also called a mascaret or bore tide, is a moving wave that travels upstream when the rising tide enters a shallow, converging estuary, reaching up to 6 meters.
Tidal harmonic constants
Tidal harmonic constants (THCs) are the amplitude and phase lag of each tidal constituent at a location; once known, they let the tide be predicted far into the future.
Tidal prism
The tidal prism is the volume of tidal water exchanged between an estuary and the sea over one tidal cycle, a central quantity in estuarine hydrodynamics.
Tidal range
Tidal range is the vertical difference in height between consecutive high and low tides at a location, varying from centimeters on lakes to 16 meters in Canadian bays.
Tidal Waves
Tidal waves: the very long-period ocean waves caused by the Moon's and Sun's gravity, seen as tides; also a common but incorrect name for tsunamis, which are unrelated to tides.
Tide
The tide is the periodic rise and fall of sea level, caused by the gravitational pull of the Moon and Sun, giving coasts two high waters most days.
Tide gauge
A tide gauge, also called a mareograph, is an instrument that continuously records water level relative to a fixed land reference, supporting navigation, tsunami warning, and sea level studies.
Tide pool
A tide pool, also called a rock pool or tidal pool, is a pocket of seawater left in a rocky shore depression when the tide recedes, sheltering dense marine life.
Tide table
A tide table is a published or electronic listing of predicted times and heights of high and low water at a port, used by mariners and coastal engineers.
Time of concentration
The time of concentration is the time runoff takes to travel from a watershed's hydraulically most distant point to the outlet, a measure dating to 1851.
Top-down control
Top-down control is the regulation of a food web by predators and grazers, notably zooplankton grazing on phytoplankton in lakes, contrasted with bottom-up nutrient control.
TOPEX/Poseidon
TOPEX/Poseidon was a joint NASA and CNES satellite mission launched in 1992 that used radar altimetry to measure sea-surface height across the global ocean, beginning the precise satellite record of sea-level rise.
TOPMODEL
TOPMODEL, a physically based semi-distributed rainfall-runoff model proposed by Keith Beven and Mike Kirkby in 1979, predicts streamflow using a topographic index and remains widely used in hydrology.
Topographic wetness index
The topographic wetness index (TWI) is a terrain-derived quantity, ln(a/tanβ), combining upslope contributing area and slope, developed by Keith Beven and M. J. Kirkby in 1979.
Total nitrogen
Total nitrogen (TN) is the sum of all forms of nitrogen in a water sample, including nitrate, nitrite, ammonia, and organic nitrogen, and a core indicator in lake monitoring.
Total phosphorus
Total phosphorus (TP) is a water-quality measurement of all phosphorus in a water sample regardless of chemical form, obtained by converting every phosphorus compound to orthophosphate before analysis.
TR-55 (hydrology)
TR-55, Technical Release 55, is a USDA publication presenting simplified procedures for estimating storm runoff volume, peak discharge, and storage volumes in small United States watersheds.
Tracer test
A tracer test introduces a tracer such as a fluorescent dye, salt, or isotope into water and monitors its arrival downstream to characterize groundwater flow paths, velocities, and connectivity.
Transient storage
Transient storage is the temporary detainment of stream solutes in slow-moving zones like eddies and porous gravel, forming the basis of the transient storage model introduced by Bencala and Walters in 1983.
Transmissivity (hydrogeology)
Transmissivity is an aquifer property measuring the rate water is transmitted through a unit width under a unit hydraulic gradient; it equals hydraulic conductivity times aquifer thickness.
Transpiration
Transpiration: movement of water vapor from soil through plants out of leaf stomata; dominant terrestrial water flux, over 60% of evapotranspiration, driven by cohesion-tension, studied since Stephen Hales (1727).
Trieste (bathyscaphe)
Trieste was a deep-diving research bathyscaphe designed by Auguste Piccard, built in Italy, and launched in 1953; in 1960 Jacques Piccard and Don Walsh piloted it to the Challenger Deep.
Triple divide
A triple divide, also called a triple watershed or hydrological apex, is where two continental divides intersect, letting water drain into three different watersheds, as at Montana's Triple Divide Peak.