Watershed Quiz 5

Question 1

Evaporation

Answer 1

Net loss of water from a surface due to
1.water going from liquid to vapor
2.net transfer or water vapir to atmosphere

Question 2

Conditions necessary for evaporation

Answer 2

Water + energy = evaporation
And must coincide at the same time

Question 3

Evaporation dominant controls

Answer 3

-High VPD = faster water vapor moves from evaporating surface
-Distance from ea to es drives evaporation
-wind drives evaporation rates
-atmospheric demand = (es-ea)

Question 4

Evaporation fomula

Answer 4

E=Cu(es-ea)
U= wind
C=constant

Question 5

VPD on windy day

Answer 5

Windy day keeps VPD large because wind keeps ea low

Question 6

Soil water evaporation

Answer 6

Saturated= similar rates to free water
Dry=rates slow but don’t stop

Unsaturated soils mean less evaporation

Question 7

Why do unsaturated soils have less evaporation

Answer 7

-disconnection of soil water from atmosphere
-adhesion of water to soil
-build-up of water vapor in pore spaces

Question 8

Do finer textured soils or coarse soils have faster evaporation rates?

Answer 8

Finer soils because soils can cling to surface

Question 9

What is evaporation like for soils under a canopy?

Answer 9

E is minor because
-interception from canopy
-understory and litter insulate
-reduced wind speed
-transportation of canopy increases ea

Question 10

Transpiration

Answer 10

Evaporation from within the leaves of plants
Aka the soil plant atmosphere continium = pathway soil water takes through a plant back to the atmosphere

Question 11

Stomata transpirstion

Answer 11

Inside stomata opening VPD is high outside is low VPD this causes transpiration. VPD and wind still relevant to transpiration

Question 12

Plant physiology for T

Answer 12

-hydrualic conductivity
-xylem dysfunction
-stomatal control

Question 13

Hydraulic conductivity

Answer 13

The ease at which water moves through porouos medians, it’s greater in hardwoods due to vessel elements

Question 14

Xylem

Answer 14

Transport tissue of vascular plants

Question 15

Tracheids and vessel elements

Answer 15

Tracheid = conifer + hardwood
Vessel element = hardwood only, more susceptible to xylem dysfunction

Question 16

Water potential

Answer 16

-Quantifies the forces causing water to move in plants
- units PA, force per unit area
-water moves from high to low water potential
-defined as a measure of the potential energy of water due to its position, configuration, or quantity

Question 17

Water potential - pressure potential

Answer 17

A measure of the outward pressure of water on a cell walls , thus usually positive in living cells
-negative in xylem because water column is under tension
-pull tension (neg)
-push tension (pos)

Question 18

Xylem dysfunction

Answer 18

Cavitation or embolism(gas bubble)
-decreases hydraulic conductivity increasing stress

Question 19

Stomatal control

Answer 19

-High VPD but low ground water can lead to xylem dysfunction
-dried out soil leads to change of tension in the water columns
-this xylem dysfunction can be avoided with stomatal closure

Question 20

Measurements of ET

Answer 20

-Evaporation pan
have to use a coefficient because pan is above ground
-lysimeters
Often used for soil E
-water balance
ET = P-Q

Question 21

PET (potential evapotranspiration)

Answer 21

The amount of water consumed in a unit of time by
-a short green crop
-completely shading the ground
-of uniform height
-AND NEVER SHORT OF WATER

Estimates of ET are trying to estimate for PET

Question 22

Two models of ET

Answer 22

-penma Monteith method(this model accounts for energy supply and mechanism of water movement and vegetation control over rate of T)
-Thorn waid method

Question 23

Estimates of PET

Answer 23

Calculated from meteorological data
-represents max ET possible
-actually ET is < or RARELY = PET