3.Evaporation

Question 1

Simplest form of evaporation is..

Answer 1

freewater evaporation

• when water molecules are only in contact with other water molecules
• ex: S Sask River

Question 2

Evaporation from free water surfaces is promoted by:2

Answer 2

– External or meteorological factors

– Internal or lake factors

Question 3

Evaporation from bare soil surfaces is promoted by :2

Answer 3

– External or meteorological factors

– Soil factors

Question 4

Evaporation from vegetated surfaces is promoted by:3

Answer 4

– External or meteorological factors
– Soil factors
– Vegetation factor

Question 5

3 External Factors promoting evap

3 Internap Factors Promoting Evap

Answer 5

• External factors
– Solar energy
– Humidity
– Diffusion and advection

• Internal factors – Salinity
– Water depth
– Surface area

Question 6

.water vapour is constantly experiencing both upforce by _______ and downforce by _______
-how big they are relative to each other determines evaporation

Answer 6

vapourization

condensation

Question 7

(Solar Radiation/Temperature) _______ is the best way to predict evaporation over time

Answer 7

Insolation

• radiation gives you the amount of available energy
• temperature does not drive evaporation

Question 8

Why are the great lakes not as dependent on insolation for evaporation?

Answer 8

The great lakes store a lot of energy

-it means that they are not as dependent on incoming energy

Question 9

Why do evaporation lines extend south over the cordillera?

Answer 9

lines of evaporation over cordillera bend south because of the mountains’ altitude
-higher altitude means lower evap

Question 10

______ determines insolation which determines _____

Answer 10

latitude

evaporation

Question 11

.water evaporates _____ in dry air

.water evaporates _____ into humid air

Answer 11

fastslow

Question 12

Southern most points of canada experience about ___klyper year of insolation

Answer 12

40

Question 13

Relative humidity has an _____ pattern to temperature

Answer 13

inverse

Question 14

Evaporation from free water surfaces is affected by 3 external and 3 internal factors: be specific

Answer 14

• External factors – Solar energy – Humidity – Diffusion and advection
• Internal factors – Salinity – Water depth – Surface area

Question 15

Dalton’s Law of Evaporation

Answer 15

E = f(u) (esat – eact)

E is the evaporation rate (cm day-1) f(u) is a function of the wind speed u esat is the saturated vapour pressure at the temperature of the water surface (mb) eact is the actual vapour pressure at the at thetemperature of the air (mb) u is the windspeed (km day-1) f(u) = 1.46 x 10-4 u

Question 16

How does wind allow for more evaporation?

Answer 16

Advection takes place with wind
-it DISPERSES the humid air from the surface allowing for more evaporation
– Redistribution of large volumes of air
– Mixing of high humidity and low humidity air

Question 17

diffusion

Answer 17

the movement of particles from an area of high concentration to an area of low concentration. For diffusion to work, the particles must be able to move around. This means that diffusion does not happen in solids – the particles in a solid can only vibrate and cannot move from place to place

– Redistribution at molecular level
– Random movement of molecules
– From high to low concentration – Can take place in still air

Question 18

How does the depth of a large water body compare to a small water body over a year?

Answer 18

Large water body:
Evaporation is at about 50mm and jumps to 125 over the winteras stored energy in used

Small water body evaporates about 125mm rate over the warmer months and then dops to 20mm over the winter as it has no stored energy to use

Question 19

.if we are looking at saline water, it is __% less evaporation because of salt vs fresh

Answer 19

3

Question 20

______ of water determines the amount of energy stored in a water body

Answer 20

volume

Question 21

Class A eVAPORATION pAN

Answer 21

has no vapour blanket and cannot store energy as it is too small in termsofvolume

– Pan receives energy through radiation and conduction through base and sides

Question 22

Vapour Blankets

Answer 22

Vapour blankets on large water bodies limits evaporation unless there is HIGH wind
-surface area determines whether vapour blankets can develop

Question 23

Pan Coeffecient

Answer 23

• The ratio of the amount of evaporation from a large body of water to that measured in an evaporation pan
• to relate pan evaporation to lake evaporation you must use the “pan coefficient”

Figure 7-6:

• pan coefficient is less than average during rainy season (Feb,March,Apr)
• pan coefficient is higher than average after the summer season as the lake gained and held energy over the summer and uses it when the temperature start to drop(sep,oct,nov,dec). The pan however, gets colder as it cannot store energy in such a small amount of water.

Question 24

The discharge is 4.2 l s-1 at 7:05 pm, and 9.6 l s-1 at 7:12 pm. The average discharge during this period is ____________ l s-1. In this period, there are __________ seconds. Every second, the volume of water flowing by is ______________ l. Over this entire period, the total volume of water flowing by is ______________ l.

Answer 24

6.9

420

6.9

2898

Question 25

Evaporation from bare soil surfaces 2 Major Factors and 2 minor factors

Answer 25

``` • Major factors – Moisture content – Capillary characteristics • Minor factors – Albedo – Seasonality of bare soil conditions ```

Question 26

Evaporation from bare soil surfaces 2 Major Factors and 2 minor factors

Answer 26

``` • Major factors – Moisture content – Capillary characteristics • Minor factors – Albedo – Seasonality of bare soil conditions ``` .Biggest difference between free water surface and soil surface is moisture supply and its replenishment

Question 27

3 phases of soil

Answer 27

Soil consists of 3 different phases(see picture of microscopic soil): a) solid particles, b) Pore Space(water)(soil solution) c) Gaseous (soil air)

Question 28

2 Important soil characteristics:

Answer 28

.particle size distribution: distribution of solid particles like clay, silt, and sand .pore size distribution: distribution of small, medium, and large pores

Question 29

= < 2 microns = >2 microns but <64 microns = >64 microns but < 2mm = >2mm

Answer 29

Clay= finer then 2 microns Silt=64 microns is boundary between silt and sand sand= gravel=>2mm

Question 30

_____microns in a mm

Answer 30

1000

Question 31

Volumetric Soil Moisture content Versus Gravimetric Soil Moisture content in terms of units

Answer 31

= m3 water/m3 soil or % =kg water/kg dry soil or %

Question 32

What allows for more capillary rise..

Answer 32

.capillary rise is affected by space, the narrower the space the farther it can move

Question 33

Capillary Rise

Answer 33

the only thing that changes and effects change in the capillary rise equation is the radius of the space it is within

Question 34

bigger the pore size means the _____(faster/slower) the water will move

Answer 34

faster

Question 35

Deep ground water table= Shallow Ground Water table= In terms of capillary rise

Answer 35

Deep ground water table= means only specific(smaller) pore sizes can move water to surface -evaporation would be low Shallow ground water table= means all pore sizes can move water to surface -evaporation would be high

Question 36

Evaporation from Vegetation External factors:3 Soil Factors:1 Plant Factors:1

Answer 36

• External factors – Available energy – Humidity – Diffusion and advection • Soil factors – Control flow of water to plant • Plant factors – Control transpiration of plant to atmosphere

Question 37

Describe a diagram of plant transpiration starting with water in the soil

Answer 37

1. Water taken up by plant hairs 2. Taken up and transported by XYLEM 3. In the leaves water in held in the air spaces where transpiration occurs out of the STOMA - plant can control water levels by opening and closing STOMA

Question 38

Potential Evapotranspiration

Answer 38

Common Theme from the 2 definitions belowis that there is NO LACK OF WATER – The water loss which will occur if at no time there is a deficiency of water in the soil for use of vegetation – Evaporation from an extended surface of short green crop, actively growing, completely shading the ground, of uniform height, and not short of water

Question 39

Define Field Capacity and Wilting Point

Answer 39

* Field capacity – Soil moisture content when soil has been drained by gravity (e.g. for 48 hours) * Wilting point – Moisture content at which vegetation can no longer extract water from the soil

Question 40

Albedo of Water= Snow(old and new)= Deciduous Forest= Coniferuous Forest=

Answer 40

0. 05-0.15 0. 30-0.90 0. 15-0.20 0. 05-0.15 - absorves more then reflects so it would appear darker

Question 41

Lysimeter

Answer 41

is put underground at water table level and uses afloat to always know at what level the water table is

Question 42

Eddy Covariance Measurements

Answer 42

used o measure water vapour movement from and to atmosphere | -sonic waves