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

- -

++

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