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Water use and the water cycle
Water use and the water cycle

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Monday, 8 Aug 2022, 08:58
Site: Open Learning
Course: Water use and the water cycle (S278_12)
Glossary: S278_12 Glossary


The combined effects of evaporation and transpiration.


A measure of how close air is to saturation with water vapour.

Hydraulic conductivity

A measure of the volume of water that will flow through a unit cross-sectional area of rock per unit time, under a unit hydraulic gradient and at a specified temperature: K in the

Darcy’s law equation.

Hydraulic gradient

The slope of a water table.

Hydrological cycle

Another name for the water cycle.


Hydrologically effective precipitation

The quantity of water available from underground or from rivers in an area, given by the excess of precipitation over actual evapotranspiration.


The study of water movement on and beneath the ground, and the physics and chemistry of water.


The parts of the Earth that are mainly composed of water.



The managed watering of crops so they can be grown in areas where they could otherwise not be grown, or to improve the yield.



Meteoric water

Fresh water derived by condensation from the atmosphere and which accumulates as surface water or underground water.


Potential evapotranspiration

The maximum evapotranspiration that could take place given an unlimited supply of moisture.


The process involved or the water that is transferred in solid or liquid form from the atmosphere to the Earth’s surface.


When used in connection with the water cycle, this is a part of the hydrosphere that stores water temporarily. Also a means of artificial water storage.

Residence time

The average time that water stays in a reservoir before moving to another reservoir; e.g. the average time that a water molecule spends in the atmosphere before falling to the ground as rain or snow.


Saline intrusion

A wedge of seawater under fresh groundwater near a coastline, caused by excessive groundwater extraction.

Saline water

Surface water with a high TDS; this is seawater in the oceans and some lakes.


The accumulation of salts in the soil that may occur with irrigated agriculture.


The process by which plants draw water from the soil and transfer it to their leaves, from which it evaporates through pores in the leaf system.

Water cycle

The natural cycle by which water is circulated between the Earth’s surface (on or under it) and the atmosphere. In essence, water is evaporated from the oceans, forms clouds, is precipitated on land as rain, hail or snow, and then flows in rivers, glaciers or underground to the sea, where it is evaporated again.