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 reservoir
4. Water and climate change
Outline:
1. Reservoirs
2. Movement among
reservoirs
3. Storage and “Residence
time”
in a reservoir
A Simple overview of the hydrologic cycle
Ocean Storage
What percent of
Earth’s water is
stored in the
oceans?
Does the volume of
the world’s oceans
ever change?
20,000 years ago: LOWER
Sea level ~400 ft lower )
than today
120,000 years ago: HIGHER
Sea level 18 ft higher than today
3M years B.P.: HIGHER
Sea level 165 ft higher
ICE AND SNOW:
glaciers, ice fields, and snowfields
How much of
all freshwater?
• 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 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/15463/f07/proj2/www/aaiordac/images/clouds.jpg
Distribution of Earth’s Water
Outline:
1. Reservoirs
2. Movement among
reservoirs
3. Storage in a reservoir
4. Water and climate change
5. Environmental frameworks
The hydrologic cycle:
Active model
•http://www.in.gov/idem/water/kids/waterpix/watercycleimage2.gif
Processes moving water through the
cycle… key Atmosphere Transport
What percent of the
water in the
atmosphere comes
from evaporation?
•Evaporation
90%
•Transpiration
10%
Subsurface Water movement
Outline:
1. Reservoirs
2. Movement among
reservoirs
3. Storage in a reservoir
4. Water and climate change
5. Environmental frameworks
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.)
GLOBAL NET WATER BALANCE
mm/day
Tropics:
Subtropics:
Convergence Divergence
Evaporation
Precipitation
Evap-Precip
Latitude
High Latitude:
Convergence
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,
Lake Mead: May, 2000
26 26
Source: NASA Earth Observatory
Lake Mead: May, 2003
27 27
Source: NASA Earth Observatory
Outline:
1. Reservoirs
2. Movement among
reservoirs
3. Storage in a reservoir
4. Limitations:
Water and climate
Climate Change:
Increases Water Vapor in the atmosphere
8
Vapor Pressure (kPa)
7
6
5
4
3
Atmosphere can hold
more water
2
1
0
-20
-10

0
10
20
30
40
o
Temperature ( C)
29 29
Source: Chow et al., 1988
Climate Change: water balance
• Evaporation (E)
Evaporation
– generally increases across
the Earth
• Precipitation (P)
– more locations specific,
increases and decreases
• Runoff/recharge (P-E)
Runoff
CRB
Model predictions of change in runoff
Precipitation
for double CO2 concentrations.
30
Source: Held and Soden, 2006
Climate Change – Runoff
• Precipitation trends
controlled by wind
circulation
• Trends intensify due to
climate change:
– dry areas become drier
– wet areas become wetter
31
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
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
33
Outline:
1. Reservoirs
2. Movement among
reservoirs
3. Storage in a reservoir
4. Water and climate change
5. Environmental framework
A framework for thinking about
water issues
quantity
direct
human
health
environment
quality
The example of Grazing
Public supply, 11%
Domestic, >1%
Agriculture, 36%
Industrial, 5%
Mining, >1%
Thermoelectric, 48%
from USGS,
2000
A breakdown
of water use in
the US,
consumptive +
returned
US water withdrawals and
consumptive use, 1960-95
Consumptive use vs.
renewable water supply
1995
USGS
Irrigation in the US
Total withdrawals, 2000
USGS
Water use in Illinois
1950-1998, excluding power generation
Illinois State Water Survey
Regional
changes in
storage
1996-7
The Ogallala, the largest freshwater aquifer
in the world. Saturated thickness
1980-1997 
Teleconnections in the hydrologic cycle
4
before
after
2
Jan
Jul
Precip, mm/yr
Regional to global effects on precipitation:
model results from deforesting Amazonia
0
Dec
Forests
Grasslands
8
before
after
4
Jan
Jul
Precip, mm/yr
Croplands
0
Dec
Avissar and Werth (2004),
Journal of Hydrometeorology
Hydrological Cycle
http://watercycle.gsfc.nasa.gov/