Hydrologic CycleEstimated Lesson Time: 20 minutes

Introduction

The hydrological cycle involves the continuous circulation of water in the Earth-Atmosphere system. At its core, the water cycle is the motion of the water from the ground, to the atmosphere, and back again. Of the many pro-cesses involved in the hydrologic cycle the most important are:

• Evaporation (number 1 on next page) - Transformation of liquid into gas, in this case water into water vapor. When solids (snow/ice) are converted directly to gas (water vapor), this process is called sublimation (number 3).

• Transpiration (number 2) – Water that moves through the leaves of plants. Water evaporates from leaves.

• Condensation (number 4) – Conversion of water vapor into water drop-lets. Most common are clouds and rain (also fog, mist, dew, or frost).

• Precipitation (number 6) – Coalescence (sticking together) of tiny water droplets creates larger drops which fall to Earth.

• Infiltration (number 8) – Precipitation that moves into the soil.• Runoff (number 9) – Precipitation that does not infiltrate into the soil,

and runs off into streams, lakes, rivers, and oceans.

Prepared by:Stephanie Bowen, Extension Assistant,Oklahoma MesonetOklahoma State University

Reviewed by:Cathy Allen, Assistant Extension Specialist, 4-HOklahoma State University

Oklahoma State University, U. S. Department of Agriculture, State and Local governments co-operating. Oklahoma State University in compliance with Title VI and VII of the Civil Rights Act of 1964, Executive Order 11246 as amended, Title IX of the Education Amendments of 1972, Americans with Disabilities Act of 1990, and other federal and state laws and regula-tions, does not discriminate on the basis of race, color, national origin, gender, age, religion, disability, or status as a veteran in any ofits policies, practices, or procedures.

Lesson 3 - Hydrologic CycleOklahoma’s Weather Network

1. E

vapo

ratio

n

4. C

onde

nsat

ion

6. P

reci

pita

tion

2. T

rans

pira

tion

4. C

onde

nsat

ion

1. E

vapo

ratio

n

9. S

now

mel

tR

unof

f

The

Wat

er C

ycle

10. P

lant

Upt

ake

9. G

roun

dwat

er F

low

8. P

erco

latio

n

9. S

urfa

ce F

low

9. S

urfa

ce F

low

8. In

filtr

atio

n

3. S

ublim

atio

n

7. D

epos

ition

1. E

vapo

ratio

n is

the

c

hang

e of

sta

te o

f wat

er

(a li

quid

) to

wat

er v

apor

(a

gas

). O

n av

erag

e,

abo

ut 4

7 in

ches

(120

c

m) i

s ev

apor

ated

into

th

e at

mos

pher

e fro

m

the

ocea

n ea

ch y

ear.

2. T

rans

pira

tion

is e

vap-

o

ratio

n of

liqu

id w

ater

from

pla

nts

and

trees

into

the

atm

osph

ere.

N

early

all

(99%

) of a

ll

wat

er th

at e

nter

s th

e

root

s tra

nspi

res

into

the

a

tmos

pher

e.

3. S

ublim

atio

n is

the

p

roce

ss w

here

ice

and

s

now

(a s

olid

) cha

nges

in

to w

ater

vap

or (a

gas

)

with

out m

ovin

g th

roug

h

the

liqui

d ph

ase.

4. C

onde

nsat

ion

is th

e

pro

cess

whe

re w

ater

v

apor

(a g

as) c

hang

es

into

wat

er d

ropl

ets

(a

liqu

id).

This

is w

hen

w

e be

gin

to s

ee c

loud

s.

5. T

rans

porta

tion

is th

e

mov

emen

t of s

olid

,

liqu

id a

nd g

aseo

us

wat

er th

roug

h th

e

atm

osph

ere.

With

out

th

is m

ovem

ent,

the

w

ater

eva

pora

ted

over

th

e oc

ean

wou

ld n

ot

pre

cipi

tate

ove

r lan

d.

6. P

reci

pita

tion

is w

ater

th

at fa

lls to

the

earth

.

Mos

t pre

cipi

tatio

n fa

lls

as

rain

but

incl

udes

s

now

, sle

et, d

rizzl

e, a

nd

hai

l. O

n av

erag

e, a

bout

3

9 in

ches

(980

mm

) of

ra

in, s

now

and

sle

et

fall

each

yea

r aro

und

th

e w

orld

.

7. D

epos

ition

is th

e

reve

rse

of s

ublim

atio

n.

Wat

er v

apor

(a g

as)

c

hang

es in

to ic

e (a

sol

id) w

ithou

t goi

ng

thro

ugh

the

liqui

d

pha

se. T

his

is m

ost

o

ften

seen

on

clea

r, co

ld

nig

hts

whe

n fro

st

form

s on

the

grou

nd.

8. In

filtra

tion

is th

e

mov

emen

t of w

ater

in

to th

e gr

ound

from

th

e su

rface

.

Per

cola

tion

is

m

ovem

ent o

f wat

er

pas

t the

soi

l goi

ng

dee

p in

to th

e

gro

undw

ater

.

9. S

urfa

ce fl

ow is

the

river

,

lake

, and

stre

am

tr

ansp

ort o

f wat

er to

the

o

cean

s. G

roun

dwat

er is

th

e flo

w o

f wat

er u

nder

-

gro

und

in a

quife

rs. T

he

wat

er m

ay re

turn

to th

e

sur

face

in s

prin

gs o

r

eve

ntua

lly s

eep

into

the

o

cean

s.

10. P

lant

upt

ake

is w

ater

take

n fro

m th

e

gr

ound

wat

er fl

ow a

nd

so

il m

oist

ure.

Onl

y 1%

of w

ater

the

plan

t

dr

aws

up is

use

d by

the

plan

t. Th

e

re

mai

ning

99%

is

pa

ssed

bac

k in

to th

e

at

mos

pher

e.

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w.s

rh.n

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jets

trea

m

5. T

rans

port

atio

n

5. T

rans

port

atio

n

6. P

reci

pita

tion

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Activity - Sweatin’ to the Coldies

Materials

Glass cups or jars - 1 per personIce cubes

Construction

1. Fill the cups/jars half full with ice.2. Add cold water to fill up the cups/jars to approximately half an inch below the rim.3. Let the cups/jars sit for about 30 minutes.4. Observe the outside of the glass.

Objective and Overview

Demonstrate the change from water vapor to liquid. Using some ice and a glass, students will chill the glass to the point where water from the atmosphere condenses on the outside of the glass.

Discussion

Ask the students where the water on the outside of the glass came from. The answer is from the atmosphere. As the water vapor molecules come into contact with the cold side of the glass, the temperature lowered to the dewpoint, condensing into a liquid.

The amount of water on the side of the glass depends upon the humidity, which is the ratio of dry air to moist air. The higher the humidity, the more moisture that air contains. The greater the moisture, the greater the water that can condense.

Relative humidity has a big impact on farming and ranching. Higher humidity can cause leaf wetting from night-time dews and lead to plant disease outbreaks. It also slows harvest and can make hay too wet to bale. Cattle and people’s heat stress in the summer is increased by high humidity, and in the winter, it makes animals and people feel colder. On the other hand, low humidity can increase fire risk. Also, plants in low humidity lose more water from their leaves.

Background

There are three states of matter: gas, liquid and solid. Water in our atmosphere exists in these three states constant-ly. As the temperature of water vapor (a gas) decreases, it will reach the point at which it turns into a liquid (called the dewpoint or the point at which dew forms). This change of state from a gas to a liquid is called condensation.

Fast Facts

It takes about one million cloud droplets to provide enough water for one raindrop.Greatest rainfall in a year was 1,041” in Assam, India (August 1880-1881).World’s one minute rainfall record is 1.23” which fell in Unionville, Maryland on July 4, 1956.Greatest snowfall in a day is 75.8” which fell in Silver Lake, Colorado, April 14-15, 1921.