Water & Transpiration
or
Water, water everywhere and all the boards did shrink.
Water, water everywhere and not a drop to drink.
J.G. Mexal
A/H 100
Middle Rio Grande Surface Water Budget
/Alb.J. 1999
Water & Transpiration
Irrigation & Water Management
• Big Water Users/ Alb. J. 9/17/96
–
–
–
–
–
–
–
City Parks
Tanoan G.C.
Arroyo del Oso G.C.
Ladera G.C.
UNM
Los Altos G.C.
NMSU
4.7 KK L/day
2.8
2.6
2.3
2.2 + 7.2(private)
1.9
6.8
The Mystery and The Magic!
• Trees can ‘pull’ water up from
the soil through the bole of the
tree into the leaves and out
into the atmosphere.
• In some cases, this is a
distance of over 300 ft!
• How do they do that????
Water is truly magical!
Which one of these is different?
• Molecule
–
–
–
–
–
–
–
–
Hydrogen (H2)
Methane (CH4)
Water (H2O)
Nitrogen (N2)
Ethane (CH3-CH3)
Oxygen (O2)
Carbon Dioxide (CO2)
Propane (CH3-CH2-CH3)
• Molecular Weight
–
–
–
–
–
–
–
–
2
16
18
28
30
32
44
44
Water is truly magical!
Which one of these is different?
• Molecule
–
–
–
–
–
–
–
–
Hydrogen (H2)
Methane (CH4)
Water (H2O)
Nitrogen (N2)
Ethane (CH3-CH3)
Oxygen (O2)
Carbon Dioxide (CO2)
Propane (CH3-CH2-CH3)
• Molecular Weight
–
–
–
–
–
–
–
–
2
16
18
28
30
32
44
44
Water is a
liquid at
room
temperature!
Hydrogen Bonding
Hydrogen weakly bonds to Oxygen, Nitrogen, and
Fluorine (you can ignore this one)
http://www.lsbu.ac.uk/water/molecule.html
http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page3.html
Chemistry for Aggies—Water Properties
• Water is a liquid at room temperature
• Water freezes at 0oC (32oF)
– Technically this is not true: water actually freezes at
about -3 to -8oC, and ‘bounces’ up to 0oC
– Water and ice can exist only at 0oC
– Freezing point reduced by the addition of other
molecules
– Gives off energy (heat)
• Water boils at 100oC (212oF)
– Boiling point increased by the addition of other
molecules
– Required input of energy (heat)
Chemistry for Aggies—Water Properties
• Water is the ‘Universal Solvent’
– Transports ions (Ca++, K+, NH4+, H2PO4-) in
transpiration stream
– Transports organic compounds (carbohydrates,
amino acids)
– Maintains complex organic compounds in
solution (DNA, proteins)
Chemistry for Aggies—Water Properties
• Have you ever used a straw to drink?
• Cohesion: Water molecules stick to each
other because of hydrogen bonding.
– This allows the giant redwoods to pull water up
through the transpiration stream.
– This gives ice its structure.
Chemistry for Aggies—Water Properties
• Have you ever blotted up a spill with a
paper napkin?
• Adhesion: Water molecules stick to other
molecules because of hydrogen bonding and
the polar nature
of the molecule.
http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page3.html
Water & Transpiration
Colligative Properties of Water
Adhesive Properties
Water & Transpiration
Colligative Properties of Water
• Boiling Point and Freezing Point of Water
Boiling point
Freezing point
Osmotic pressure
Water potential
Pure H20
100
0
0
0
1 Molal Sol’n*
100.52 OC
- 1.86 OC
- 2.27 MPa
- 2.27 MPa
1 Avogadro’s number = 6 X 1023 molecules
Chemistry for Aggies—Water Properties
• Have you ever made ice cream?
• Heat of fusion: When water changes to ice,
80 cal/g of heat is given off.
Hydrogen bonding of water
Hydrogen bonding of ice
http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page3.html
Chemistry for Aggies—Water Properties
• Have you ever made ice cream?
• Heat of fusion: When water changes to ice,
80 cal/g of heat is given off.
Ice is less
dense than
water
Hydrogen bonding of water
Hydrogen bonding of ice
http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page3.html
Water & Transpiration
Colligative Properties of Water
Cohesive Properties
Chemistry for Aggies—Water Properties
• Colligative Properties of Water
– Freezing Point of Water
• Pure water freezes at 0oC
• Molal solution freezes at -1.86oC
• Phase change requires 6 kJ/mol
– Boiling Point of Water
• Pure water boils at 100oC
• Molal solution boils at 100.52oC
• Phase change requires 41 kJ/mol
Most plant can
tolerate exposure
to ~-2oC
Chemistry for Aggies—Water
Properties
Water changing to
ice gives up heat
• Have you ever made ice cream?
• Heat of fusion: When water changes to ice, 80
cal/g (6 kJ/mol) of heat is given off.
• Pure water and ice can only
exist at one temperature (0oC or
32oF)—frost protection in the
Fall
• Adding salt reduces the
freezing point [this is why
milk+sugar+strawberries does
not freeze at 0oC and why
leaves do not freeze at 0oC]
Chemistry for Aggies—Water Properties
• Colligative Properties of Water
– Freezing Point of Water
• Pure water freezes at 0oC
• Molal solution freezes at -1.86oC
• Phase change requires 6 kJ/mol
– Boiling Point of Water
Water changing to
vapor absorbs heat
• Pure water boils at 100oC
• Molal solution boils at 100.52oC
• Phase change requires 41 kJ/mol [Vaporization]
Chemistry for Aggies—Water Properties
• Have you ever used a swamp cooler?
• Heat of vaporization: when water changes
to vapor, 540 cal/g is removed.
– Leaves are ~10oC cooler than ambient air
because of transpiration
– Misting buds in the Spring can delay heat
accumulation (GDD) and thus bud break–
providing frost protection in the Spring.
Infrared Surface Temperature Influenced
by Surface Cover
Temperature (oF)
160
Turf
Asphalt
Artificial Turf
140
120
100
80
60
40
6
8
10
12
14
16
18
Military Time (hr)
20
22
24
Infrared Surface Temperature of Artificial
Turf Influenced by Irrigation
Temperature (oF)
160
No Water
0.07" Water
0.13" Water
0.20" Water
0.26" Water
140
120
100
80
60
40
6
8
10
12
14
16
18
Military Time (hr)
20
22
24