Biogeochemical Cycles - 2
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Transcript of Biogeochemical Cycles - 2
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Biogeochemical Cycles - 2
Class Lecture Goals
1. Focus on the Water Cycle
2. Unique aspects of water
3. Three case studies1. Chehalis River Flood
2. Skagit Watershed: Loss of snow pack and glaciers
3. Urban Watersheds
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Environmental Issues• Seattle Times - PI Sunday: Gravel pits as a
a non-renewal resource
• National Geographic
Magazine - January
(Recyling)
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Reading
Science 2004
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The concern about loss of snow pack is because snow water makes up __% of
stream water in the west
1 2 3 4
0% 0%0%0%
1. 25
2. 33
3. 75
4. 100
Answer Now!
10
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Take-home messages
• Decreased snow packs
• Biggest drops, lower elevations
• Biggest drops, PNW
• Snow is melting earlier in the spring
• Disagreement: Mote vs. Taylor
• Index year (1950)
• Role of PDOs vs. climate change
• Uncertainty
• Shifts in timing of runoff
• Impacts on summer water
Premise: Glaciers, permanent snow fields and snow pack are the ‘water towers’ of the mountains
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Water Cycle
Image/Text/Data from the University of Illinois WW2010 Project
http://ga.water.usgs.gov/edu/watercyclesummary.html
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Water Cycle Details
• Properties of water
• Nature of stream flow (critical roles)
• Three cases– Chehalis River
flood– Skagit
Watershed– Urban watershed
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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.
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Unique Properties of Water
O
HH
- -
++
O
HH
- -
++
O
HH- -
++
O
HH
- -
++
O
HH
- -
++
O
HH
- -
++
O
HH
• Small molecule
• Three states: liquid, solid, gas
• Liquid from 0 - 100oC
• Takes lots of energy to change state or change temperature
• Transparent
• Solvent
• Solid vs. liquid
• Movement in plants
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Understand the behavior of a watershed
http://wa.water.usgs.gov/realtime/rt_latest_map.html
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Behavior of Water in a Watershed• Use of a hydrograph (stream gauge)
Time0 12
Dis
char
geR
ain
Agriculture
Forest
Forest-AgUrban
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Behavior of Water in a Watershed
• Westside, little or no snow
• Westside, lots of snow
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Behavior of Water in a Watershed
• Eastside, snow, NE WA
• Urban - suburban stream
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1. Chehalis River Flood
141618
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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
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2. Skagit Watershed
• Third largest on the west coast of US
• 3100 mile2 (about 1/6th in Canada)
• Major agriculture
• Major salmon
• National Park
• Seattle City Light
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Google Image of South Cascade River Watershed
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1928 2000
South Cascade Glacier from ~1850 (see blue overlay) to 2005 (see above photo).
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South Cascade Glacier Data
Volume of South Cascade Glacier from ~1850 to 2005. Data for 1850 is an estimate.
Gla
cier
Vol
ume
(km
3)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1850 1900 1950 2000 2050 2100
Year
1928
2001
1890
2005
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3. Urban Watersheds - Thornton Creek
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Alternatives• Storage system
• Green roofs
• Example from Sea-Streets
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Close-up a Sea-Street
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In your view, which alternative seems the most viable
1 2 3
17%
59%
24%
1. Using cisterns (tanks) to collect runoff
2. Requiring green roofs
3. Using the S.E.A.-Street model
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Major (Climate) Change Issues
• Quantity of water
• Seasonal and spatial distribution
• Form of water/rain on snow
• Cloud and fog formation and spatial distribution
• Uses of water
• Loss of forests and vegetation
• Increases in impervious surfaces
Premise: Clean, fresh water is a rare resource
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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
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