the water cycle… from clouds to sea.. from sea to clouds…

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/