HYDROTEK NA YAN

Evaporation from water bodies and soil masses together with transpiration from vegetation is termed as

evapotranspiration

is the process in which a liquid

change to the gaseous state at the free

surface, below the boiling point through the

transfer of heat energy.

Evaporation

The rate of evaporation increases with an increase in the water temperature

Temperature

helps to remove the evaporated water vapor from the zone of evaporation,

thereby creating greater scope for evaporation.

Wind

Other factors remaining the same, a decrease in atmospheric pressure (as in high altitudes areas) increases the evaporation rate.

Atmospheric Pressure

When a solute is dissolved in water, the vapor pressure of the solution is less than that of pure water and hence it causes reduction in the rate of evaporation. Under identical conditions evaporation from sea water is about 2-3% less than that from fresh water.

Soluble Salts

Deep water bodies have more heat storage capacity than shallow water bodies.

The effect of heat storage is to change the seasonal evaporation rates and the

annual evaporation remains more or less unaltered.

Heat Storage in water bodies

are water-containing pans which are exposed to the atmosphere

and the loss of water by evaporation measured in them at regular intervals.

Meteorological data, such as humidity, wind movement, air and water temperatures and

precipitation are also noted along with evaporation measurement.

Evaporimeters

simplest but the least reliable. If the unit of time is kept

very large, estimates of evaporation will be more accurate.

Water Budget Method

is application of law of conservation of energy. The energy available for evaporation is determined by considering the incoming energy, outgoing energy and energy stored in the water body over a known time interval.

Energy Budget Method

is the process by which water leaves the

body of a living plant and reaches the atmosphere as water

vapor. The water is taken up by the plant-root system and

escapes through the leaves.

Transpiration

The total amount of water loss in the form of

water vapors into the atmosphere from

surface of the soil, canopy interception,

water bodies as well as from the aerial parts

of the plants in a process known as

evapotranspiration.

The term ____ use is also used to

denote this loss by evapotranspiration.

consumptive

If sufficient moisture is always available to completely meet the needs of vegetation full covering the area, the resulting evapotranspiration is called

potential evapotranspiration (PET).

The real evapotranspiration occurring in a specific situation is called

actual evapotranspiration (AET).

is the maximum quantity of water that the soil can retain against the

force of gravity.

Field capacity

is the moisture content of a soil at which the moisture is

no longer available in sufficient quantity to sustain the plants.

Permanent wilting point

The field capacity and permanent wilting point depend upon the soil

characteristics. The difference between this two-moisture content is called

available water

is a special watertight tank

containing a block of soil and set in a field of

growing plants

lysimeters