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

Environmental Issues• Seattle Times - PI Sunday: Gravel pits as a

a non-renewal resource

• National Geographic

Magazine - January

(Recyling)

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

0% 0%0%0%

1. 25

2. 33

3. 75

4. 100

Answer Now!

10

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

Water Cycle

Image/Text/Data from the University of Illinois WW2010 Project

http://ga.water.usgs.gov/edu/watercyclesummary.html

Water Cycle Details

• Properties of water

• Nature of stream flow (critical roles)

• Three cases– Chehalis River

flood– Skagit

Watershed– Urban watershed

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

• Solid vs. liquid

• Movement in plants

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

• Westside, lots of snow

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).

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

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

17%

59%

24%

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

• 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

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