Download - Catalyst

Today’s Questions
What is the water or hydrological cycle?
What causes floods?
Review Monday
• System definition, illustration
• Biogeochemical Cycles
• Carbon cycle - Farm tour (this Thursday and
next Tuesday)
– Decomposition (C - cycle, detritus part of food
chains, foods webs)
– Food security
– Invasive plants
– Farming practices: organic, sustainable
– Urban agriculture - sustainable cities
Who cares about snow and ice?
What is an impervious surface and what
does it do water?
Are there alternatives to traditional ways
of handling urban water?
Question: Photosynthesis is a
flux or a pool?
Biogeochemical Cycles - 2
1. 1. Focus on the Water Cycle:
2. Issue of water supply: now, future
3. Understanding the behavior of water in
streams (floods, power, salmon)
4. Three case studies
1. Flux
2. Pool
3. Both
a) Floods


PNW
Pakistan flood of 2010 and US floods 2011
b) Snow and ice (mountain glaciers)
c) Urban Watersheds
Reading
Water security, supply or scarcity has
become a major topic because (pick
incorrect answer)
1.
2.
3.
4.
World’s population has
increased
As wealth increases,
consumption of meat
decreases
Agriculture depends
increasingly on
irrigation.
Glaciers and snow
coverage is
decreasing.
1
Water Cycle
Quantities of Water
• Learning about
stream flow
• Three cases
– Floods
• Washington
• Pakistan
– Role of snow &
glaciers
globally
– Urban
watershed
•
•
•
•
http://ga.water.usgs.gov/edu/watercyclesummary.html
Takehome Message: Lots of water!
Not much fresh
Not much clean fresh
Water quantity is variable!!
Water Scarcity
• Article in the Economist (& the NAS YouTube
Video) emphasized:
Stream Behavior & Floods (#1)
(1) Floods in Washington State
(2) Floods in Pakistan (2010)
(3) Floods in US (2011)
– Importance of having enough, clean water at
the right time
• Problems
– Too much or not enough
– Polluted (http://www.fic.nih.gov/News/Pages/2011climate-change-diarrheal.aspx)
– Conflicting uses
Anatomy of environmental events
of 2010 - 2011
• Key: understand how water and watersheds
behave
Understand the behavior of a watershed
http://www.klimadiagramme.de/
http://en.wikipedia.org/wiki/Pakistan
Behavior of Water in a Watershed
Rain
• Use of a hydrograph (stream gauge)
Lots
Peak Flow
0
% impervious surface
Lots
Peak Flow
Urban
Discharge
Forest
http://waterdata.usgs.gov/wa/nwis/rt
Base Flow
Base Flow
0
0
Time
12 hours
2
Floods on the Snoqualmie River
Nov 24, 1990
78,800 cfs
Jan 9, 2009
61,100 cfs
Summary: River
Behavior
Interior mountains:
• September low
• May - July high
Low elevation,
coastal mountains:
• September low
• Nov - Feb high
• Spikes with big
rain events
High elevation,
Cascade mountains:
• September low
• Nov - Dec high
• Jan - Feb low
• May - June high
• Spikes: Rain on snow
Pakistan 2010 Indus River
Floods: Reasons
• Changes in precipitation due to climate change
– Average increases slightly (warmer air holds more
water
– Increased intensity
• Rain-on-snow
– Role of clearcuts & young forests
• River system
– Land use changes
– % impervious surface
– River channel itself
• Removal of beavers
• Removal of structure (coarse woody debris)
• Channelization
Case # 2: Glaciers and Snow
• Example of a positive feedback as snow
and ice melts from warming, more
radiation is absorbed (vs. reflected
[albedo effect]): positive feedback.
• One of the most reliable indicators of
climate change
• Have a major influence on water
availability.
• North and South America, Europe, Asia
3
1913
Last 1000 years
Glacier National Park 150 to 26
Medieval
Optimum
Austrian Alps
Little Ice Age
1oC
2005
http://www.msnbc.msn.com/id/6903014
River Systems
Glaciers - Himalayas
7
2
3
4
5
6
1
Glaciers - Water Security
• Water towers of the mountains
• Supply water directly or indirectly to
billions of people
• Like aquifers, humans have been living
on capital for the last 100 plus years.
• Demand for water
– Population
– Agriculture
– Switch from eating cereals to things eating
cereals.
4
Take-home messages for PNW
3. Urban Watersheds - Thornton Creek
Glaciers, permanent snow fields and
snow pack are the ‘water towers’ of
the mountains
• Decreased snow packs
• Biggest decreases, lower elevations
• Big decreases in PNW
• Snow melts earlier in the spring
• Shifts in timing of runoff
• Impacts on summer water
• Increasing demands & uses of water
Alternatives
Close-up a Sea-Street
• Storage system
• Green roofs
• Example from Sea-Streets
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
4. All three
Major (Climate) Change Issues
Premise: Clean, fresh water is a rare resource
•
•
•
•
•
•
•
Quantity of water (+ in form of snow, ice)
Loss of mountain snow and ice
Seasonal and spatial distribution
Rainfall intensities
Loss of forests and vegetation
Increases in impervious surfaces
Demand for fresh, clean water
5
Summary: Water Cycle
• Water cycle: Quantity, Quality, Form, &
Timing
• Watershed - definition, behavior
• Climate, weather and watershed
properties
• Three cases
– Floods
– World-wide glaciers (Himalayas)
– Urban Watersheds
6