biogeochemical cycles - 2
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Biogeochemical Cycles - 2Class Lecture Goals1. Focus on the Water Cycle2. Unique aspects of water3. Understanding the behavior of water in
streams (floods, power, salmon)4. Three case studies
1. Chehalis River Flood2. Skagit Watershed: Loss of snow pack and
glaciers3. 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 2 3 4
1% 1%82%16%
1. 252. 333. 754. 100
Take-home messages
• 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
Premise: Glaciers, permanent snow fields and snow pack are the ‘water towers’ of the mountains
Glacier National Park Austrian Alps
1913
2005
150 to 26
http://www.msnbc.msn.com/id/6903014
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
HH
- -
++
O
HH
- -
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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 (C as skeleton of life, water as medium of life)
• Density of water (liquid vs. solid)
Understand the behavior of a watershed
http://wa.water.usgs.gov/realtime/rt_latest_map.html
Behavior of Water in a Watershed• Use of a hydrograph (stream gauge)
Time0 12
Dis
char
geR
ain
Agriculture
Forest
Forest-AgUrban
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
141618
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• Major salmon• National Park• Seattle City Light
Google Image of South Cascade River Watershed
1928 2000
South Cascade Glacier from ~1850 (see blue overlay) to 2005 (see above photo).
2005
South Cascade Glacier DataVolume 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
Take home lesson: snow pack is less, melting earlier, stored water in glaciers is being depleted
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 2 3
20%
66%
14%
1. Using cisterns (tanks) to collect runoff
2. Requiring green roofs
3. Using the S.E.A.-Street model
Major (Climate) Change Issues
• 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
Premise: Clean, fresh water is a rare resource
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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