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The Water Cycle… from clouds to sea.. from sea to clouds…
The hydrologic cycle: Water cycle as an active model
• Active processes
– Precipitation events: rain, fog, mist, snow
– Infiltration and ground and surface water flow events
– eventual discharge into creeks and rivers
– root adsorption– Water enters back into the
atmosphere in the form of water vapor
– Vapors condense, form clouds, and result in another precipitation event
Animation from: http://www.nps.gov/olym/hand/process/wcycle.gif
The Water Cycle on the Coast…. from sea to land …….. is a microcosm of the global cycle
http://www.hko.gov.hk/education/edu01met/wxphe/ele_fog_fig2e.png
The Water Cycle Globally
Outline:1. Reservoirs 2. Movement among
reservoirs
3. Storage and “Residence time”
in a reservoir4. Water and climate change5. Environmental frameworks
for thinking about water
Outline:1. Reservoirs 2. Movement among
reservoirs
3. Storage and “Residence time”
in a reservoir4. Water and climate change5. Environmental frameworks
for thinking about water
A Simple overview of the hydrologic cycle
Ocean Storage
What percent of Earth’s water is stored in the oceans?
20,000 years ago: LOWER20,000 years ago: LOWERSea level ~400 ft lower )Sea level ~400 ft lower )than todaythan today
120,000 years ago: HIGHER 120,000 years ago: HIGHER Sea level 18 ft higher than todaySea level 18 ft higher than today
3M years B.P.: HIGHER3M years B.P.: HIGHERSea level 165 ft higherSea level 165 ft higher
Does the volume of the world’s oceans
ever change?
ICE AND SNOW:glaciers, ice fields, and snowfields
• Glacial ice covers 11% of all land• Represents a large % of all freshwater• Mountain snowfields are “reservoirs” for many
water-supply systems– 75% in Western States
How much of How much of all freshwater?all freshwater?
How much ground water?
• Ground water occurs only close to the surface
Surface Water:Lakes & Swamps & Rivers
• Lakes swamps account for less than 0.3% of all fresswater:
- 20% is in the Great Lakes
- 20% is in Lake Baikal in Siberia
Storage in the atmosphere:
• 0.001%
• Water vapor • Clouds,
condensed water vapor
http://www.cs.cmu.edu/afs/andrew/scs/cs/15-463/f07/proj2/www/aaiordac/images/clouds.jpg
Distribution of Earth’s Water
Outline:1. Reservoirs 2. Movement among
reservoirs
3. Storage in a reservoir4. Water and climate change5. Environmental frameworks
for thinking about water
•http://www.in.gov/idem/water/kids/waterpix/watercycleimage2.gif
The hydrologic cycle: Active model
Processes moving water through the cycle… key Atmosphere Transport
•EvaporationEvaporation
•TranspirationTranspiration
90%90%
10%10%
What percent of the What percent of the water in the water in the atmosphere comes atmosphere comes from evaporation?from evaporation?
Subsurface Water movement
Outline:1. Reservoirs 2. Movement among
reservoirs
3. Storage in a reservoir4. Water and climate change5. Environmental frameworks
for thinking about water
Mass Balance: Storage, a consequence of movements
Generally:Inflow (I) – Outflow (O) = Net balance
Globally, we turn this around::Outflow (O) – Inflow (I) = Net balance Evaporation (E) - Precipitation (P)E – P = Net Balance
(Also called the continuity equation,conservation of mass.)
mm
/d
ay
EvaporationPrecipitatio
n
Evap-Precip
Latitude
Tropics:Convergence
Subtropics:Divergence
High Latitude:Convergence
GLOBAL NET WATER BALANCE
Mass Balance: Storage, a consequence of movements
When thinking on a local scale of land use:Inflow (I) – Outflow (O) =
± Change in storage (S)
I - O = ± ∆S
(Also called the continuity equation,conservation of mass.)
26 26
Source: NASA Earth Observatory
Lake Mead: May, 2000
27 27
Source: NASA Earth Observatory
Lake Mead: May, 2003
Outline:1. Reservoirs 2. Movement among
reservoirs
3. Storage in a reservoir4. Limitations:
Water and climate change
5. Framework for thinking about water
29 29
Climate Change: Increases Water Vapor in the atmosphere
0
1
2
3
4
5
6
7
8
-20 -10 0 10 20 30 40
Temperature (oC)
Va
po
r P
ress
ure
(kP
a)
Source: Chow et al., 1988
Atmosphere can hold more water
30
Climate Change: water balance
• Evaporation (E)– generally increases across
the Earth • Precipitation (P)
– more locations specific, increases and decreases
• Runoff/recharge (P-E)
Source: Held and Soden, 2006
CRBModel predictions of change in runoff for double CO2 concentrations.
Runoff
Evaporation
Precipitation
31
Climate Change – Runoff
• Precipitation trends controlled by wind circulation
• Trends intensify due to climate change:– dry areas become drier– wet areas become wetter
Source: Maidment CE 394K.2 class notes, 2008
Climate Change: Modeled runoff
Annual average of change in runoff compared to the global modeling average.
Source: Milly et al., 2008
33
Climate Change: Water Vapor• The atmosphere can “hold more water vapor” at
higher temperatures• This produces more clouds, which can act to both
warming• Therefore, increased water vapor in the
atmosphere will further act to increase surface temperature and evaporation
• This will further increase atmospheric water vapor concentrations
• BUT, same amount of water, redistributed in reservoirs
Outline:1. Reservoirs 2. Movement among
reservoirs
3. Storage in a reservoir4. Water and climate change5. Environmental framework
for thinking about water
A framework for thinking about water issues
quantity quality
directhumanhealth
environment
The example of Grazing
A breakdown of water use in
the US,consumptive +
returned
Public supply, 11%
from USGS, 2000
Domestic, >1%
Agriculture, 36%
Mining, >1%
Industrial, 5%
Thermoelectric, 48%
US water withdrawals and consumptive use, 1960-95
Consumptive use vs. renewable water supply
1995
USGS
Irrigation in the USTotal withdrawals, 2000
USGS
Water use in Illinois
1950-1998, excluding power generation
Illinois State Water Survey
The Ogallala, the largest freshwater aquifer in the world. Saturated thickness
1980-1997 1996-7
Regional changes in
storage
Regional to global effects on precipitation: model results from deforesting Amazonia
before after
Teleconnections in the hydrologic cycle
2
4
0Jan DecJul
4
8
0Jan DecJul
Pre
cip
, m
m/y
rP
reci
p,
mm
/yr
before after
Avissar and Werth (2004), Journal of Hydrometeorology
Grasslands
Croplands
Forests
Hydrological Cycle
http://watercycle.gsfc.nasa.gov/