LESSON 5

Question 1

It’s the water returned to the air, from a liquid to gaseous state

Answer 1

Evaporation

Question 2

Evaporation from plants

Answer 2

Transpiration

Question 3

Combination of evaporation and transpiration

Answer 3

Evapotranspiration

Question 4

Used interchangeably with evapotranspiration

Answer 4

Consumptive Use

Question 5

It refers to the sum of evapotranspiration and water used by the plants for tissue building processes

Answer 5

Consumptive Use

Question 6

Importance of Evapotranspiration

Answer 6

For water conservation
For determining irrigation requirements for crops
For determining water storage in reservoir

Question 7

Factors affecting Evaporation

Answer 7

1. Meteorological Factors
2. Nature of the evaporating surface
3. Effects of water quality

Question 8

Meteorological Factors

Answer 8

Solar radiation directly affects temperature.

Evaporation is directly proportional to air temperature.

Vapor pressure affects the degree of air saturation.

Evaporation is fast in dry air.

Evaporation is directly proportional to wind speed.

Question 9

TRUE OR FALSE

All surface exposed to precipitation are
potentially evaporating surfaces

Answer 9

True

Question 10

TRUE OR FALSE

The larger the area exposed to evaporation, the slower the rate of evaporation.

Answer 10

False; Faster

Question 11

Evaporation varies ____________ with salinity of water

Answer 11

Inversely

Question 12

TRUE OR FALSE

Evaporation rate is faster in fresh water due to low vapor pressure.

Answer 12

False; High vapor pressure

Question 13

For saturated soils, evaporation may be similar to that from an ____________. As soil moisture decreases, the rate of evaporation ___________.

Answer 13

open free-water surface,
also decreases

Question 14

Helps in moisture conservation
because they decrease the rate of
evaporation.

Answer 14

Mulches

Question 15

Measurement of Evaporation

Answer 15

Evaporation pan
Lysimeter or Evapotranspirimeters

Question 16

In order to make a measurement that takes these factors into account, it is possible to physically isolate a portion of land from its surroundings and continuously weigh it to monitor changes in water content.

Answer 16

Lysimeter or Evapotranspirimeters

Question 17

Methods of Determining ET

Answer 17

1. Field Experimental Plots
2. Soil Water Studies
3. Integration Method
4. Inflow-outflow method

Question 18

the quantity of water applied in these plots is kept small to avoid deep percolation losses and surface runoff is measured

Answer 18

Field Experimental Plots

Question 19

samples are taken at various depths in the root zone

Answer 19

Soil Water Studies

Question 20

the water used by plants and evaporation from the water and soil surfaces are combined for the entire area involved

Answer 20

Integration Method

Question 21

inflow into the area (precipitation), outflow from the area and change in groundwater level are evaluated

Answer 21

Inflow-outflow method

Question 22

Categories of Methods of Predicting Evaporation and Evapotranspiration

Answer 22

1. Mass transfer
   2 Energy of Balance
2. Empirica Methods

Question 23

water moves away from evaporating and transpiring surfaces in response to the combined phenomena of turbulent mixing of the air and the vapor pressure gradient

Answer 23

Mass transfer

Question 24

requires measurements of wind and humidity at two or more elevations

Answer 24

Mass transfer

Question 25

heat is required for evaporation of water, so if there is no change in water temperature, the net radiation or heat supplied is a measure of evaporation

Answer 25

Energy balance

Question 26

developed from experience and field research based on assumption that the energy available for evaporation is proportional to temperature

Answer 26

Empirical Methods