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Biogeochemical Cycles - 2
Class Lecture Goals
1. Focus on the Water Cycle
2. Unique aspects of water
3. Understanding the behavior of water in
streams (floods, power, salmon)
4. Three case studies
1. Chehalis River Flood
2. Skagit Watershed: Loss of snow pack and
glaciers
3. Urban Watersheds
Reading
Science 2004
The concern about loss of snow pack is
because snow water makes up __% of
stream water in the west
1%
1.
2.
3.
4.
16%
82%
2
3
1%
25
33
75
100
1
4
Take-home messages
Premise: Glaciers, permanent snow fields and snow pack are
the ‘water towers’ of the mountains
• Decreased snow packs
• Biggest drops, lower elevations
• Biggest drops, PNW
• Snow is melting earlier in the spring
• Disagreement: Mote vs. Taylor/Mass
• Index year (1950)
• Role of PDOs vs. climate change
• Uncertainty
• Shifts in timing of runoff
• Impacts on summer water
1913
Glacier National Park 150 to 26
2005
http://www.msnbc.msn.com/id/6903014
Austrian Alps
Water Cycle
• Properties of
water
• Nature of stream
flow (critical
roles)
• Three cases
– Chehalis River
flood
– Skagit Watershed
– Urban watershed
http://ga.water.usgs.gov/edu/watercyclesummary.html
Quantities of Water
• Changes in Ice
– If all glaciers & icecaps melted today the seas would rise about
230 feet (70 meters).
– During the last ice age, the sea level was about 400 feet (122
meters) lower than today.
– During the last warm spell, 125,000 years ago, the seas were
about 18 feet (5.5 meters) higher than today.
Unique Properties of Water
-
O
+H
+H
-+H
H +-
O
O
H +-
O
-+ H
H+ O
H
• Small molecule
• Three states: liquid, solid,
gas
-
O
- +H
H ++H
H
• Liquid from 0 - 100oC
H+
O
-
• Takes lots of energy to
change state or change
temperature
• Transparent
H+
• Solvent (C as skeleton of life,
water as medium of life)
• Density of water (liquid vs.
Understand the behavior of a watershed
http://wa.water.usgs.gov/realtime/rt_latest_map.html
Behavior of Water in a Watershed
Rain
• Use of a hydrograph (stream gauge)
Agriculture
Urban
Forest-Ag
Discharge
Forest
0
Time
12
Behavior of Water in a Watershed
• Westside, little
or NO snow,
Calawah,
Forks
• Westside, lots
of snow,
Nooksack,
Glacier
Behavior of Water in a Watershed
• Eastside,
snow, NE WA
• Urban - suburban
stream
1. Chehalis River Flood
18
16
14
Effects of trees vs. no trees
• Assume 100”
• Amount & type of
precipitation (ppt) no difference.
• Trees intercept ppt
•
(5 - 15%)
• Forest soil is drier:
Trees transpire
(20%)
• Snow stays colder •
under forest
•
Snow
accumulates
more slowly
under forest
Roots provide
strength
Roads are bad
2. Skagit Watershed
• Third largest on the
west coast of US
• 3100 mile2 (about
1/6th in Canada)
• Major agriculture
• Ma jor salmon
• National Park
• Seattle City Light
Google Image of South
Cascade River Watershed
2005
South Cascade Glacier
from ~1850 (see blue
overlay) to 2005 (see
above photo).
1928
2000
South Cascade Glacier Data
Glacier Volume (km3)
Volume of South Cascade Glacier
from ~1850 to 2005. Data for
1850 is an estimate.
0.7
0.6
1890
0.5
Take home
lesson: snow
pack is less,
melting earlier,
stored water in
glaciers is being
depleted
1928
0.4
2001
0.3
2005
0.2
0.1
0
1850
1900
1950
Year
2000
2050
2100
3. Urban Watersheds - Thornton Creek
Alternatives
• Storage system
• Green roofs
• Example from Sea-Streets
Close-up a Sea-Street
In your view, which alternative
seems the most viable
1. Using cisterns
(tanks) to collect
runoff
2. Requiring green
roofs
3. Using the
S.E.A.-Street
model
66%
20%
14%
1
2
3
Major (Climate) Change Issues
Premise: Clean, fresh water is a rare resource
•
•
•
•
•
•
Quantity of water (+ in form of snow, ice)
Seasonal and spatial distribution
Rain on snow
Loss of forests and vegetation
Increases in impervious surfaces
Demand for fresh water
Summary: Water Cycle
• Water cycle: Quantity, Quality, Form, &
Timing
• Properties of water
• Watershed
• Climate, geographic location and water
• Three cases
– Chehalis Flood
– Skagit Watershed
– Urban Watersheds