Ch11 Sec1 Revised

7/17/2019 Ch11 Sec1 Revised

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DAY ONE

Chapter 11

Water

Section 1: Water Resources


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Water Resources Water is essentialto life on Earth. Humans

can live for more than month without food, but

we can live for onl a few das without water.

!wo "inds of water found on Earth:

Fresh water, the water that people candrin", contains little salt.

Salt water, the water in oceans, contains

a hi#her concentration of dissolved salts.

$ost human uses for water, such as drin"in#

and a#riculture, re%uire fresh water.


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The Water Cycle Water is a renewable resource because it is

circulated in the water ccle.

&n the water ccle, water molecules travel

between the Earth's surface and the

atos!here.

( Water e"a!oratesat the Earth's surface. Water vapor rises into the air.

( )s the vapor rises, it condensesto form

clouds. Eventuall the water in clouds

falls bac" to the Earth.

!he oceans are important because alost

all of the Earth's water is in the ocean.


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#ill Nye $ Water Cycle


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The Water Cycle


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%lobal Water Distribution

)lthou#h &1percent of the Earth's

surface is covered with water, nearl

'&percent of Earth's water is salt

waterin oceans and seas.

*f the fresh water on Earth, about

&&percent is fro(enin #laciers and

polar icecaps.

*nl a small percenta#e of the wateron Earth is li%uid fresh water that

humans can use.


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%lobal Water Distribution

!he fresh water we use comes mainl from la)es and

ri"ersand from a relativel narrow +one beneath the

Earth's surface.


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Surface Water

Surface wateris all the bodies of freshwater, salt water, ice, and snow, that are

found above the #round.

!he distribution of surface water has plaed

a vital role in the de"elo!entof human

societies.

!hrou#hout histor, people have built cities

and farms near reliable sources of water.

!oda, most lar#e cities depend on surface

water for drin"in# water, water to #row crops,

food such as fish, power for industr, and

transportation.


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Ri"er Systes Streams form as water from fallin# rain

and meltin# snow drains from mountains,hills, plateaus, and plains.

)s streams flow downhill, the combine

with other streams and form ri"ers.

) ri"er syste is a flowin# networ" ofrivers and streams drainin# a river basin.

!he Aa(on Ri"ersstem is the lar#est

river sstem in the world as it drains an

area of land that is nearl the si+e ofEurope.


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Watersheds

) watershedis the area of land that is

drained b a water sstem.

!he amount of water that enters a

watershed varies throu#hout the ear.

Rapidl meltin# snow as well as sprin#

and summer rains can dramaticall

increasethe amount of water in a

watershed.

)t other times of the ear, the river sstemthat drains a watershed ma be reduced

to a tric"le.


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Watersheds


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%roundwater $ost of the fresh water that is available

for human use cannotbe seen, as it

eists under#round.

When it rains, some of the water that

falls onto the land flows into la"es and

streams.

-ut much of the water percolates

throu#h the soil and down into the

roc"s beneath.

%roundwateris the water that is

beneath the Earth's surface.


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%roundwater

)s water travels beneath the Earth's surface, it eventuall

reaches a level where the roc"s and soil are saturated with

water.

( !his level is "nown as the water table.

&n wet re#ions, the water table ma be at the Earth'ssurface.

( &n deserts, the water table ma be hundreds of meters

beneath Earth's surface.

!he water table has !ea)s and "alleys that match the

shape of the land above. roundwater tends to flow slowl

from the pea"s to the valles.


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%roundWater *ideo


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A+uifers

)n a+uiferis a bod or roc" or sediment thatstores #roundwater and allows the flow of

#roundwater.

!he are an i!ortantwater source for man

cities.

!he water table forms the u!!er boundaryof an

a%uifer, and most a%uifers consist of materials

such as roc), sand, and -ra"elthat have a lot of

spaces where water can accumulate.

roundwater can also dissol"eroc" formations,fillin# vast caves with water, creatin# under#round

la"es.


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.orosity

.orosityis the percenta#e of

the total volume of a roc" or

sediment that consists of open

spaces.

Water in an a%uifer is stored in

the pore spaces and flows form

one pore space to another.

!he more porous a roc" is, themore water it can hold.


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.ereability

.ereabilityis the abilit of a roc" or sediment to let

fluids pass throu#h it open spaces or pores.

$aterials such as -ra"elthat allow the flow of water are

permeable. $aterials such as cla or #ranite that stop

the flow of water are impermeable.

!he most productive a%uifers usuall form in permeable

materials, such as sandstone, liestone, or layers of

sand and -ra"el.


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The Rechar-e /one !o reach an a%uifer, surface water must

travel down throu#h permeable laers ofsoil and roc".

Water cannot reach an a%uifer from places

where the a%uifer is covered b

impermeable materials.

!he rechar-e (oneis an area in which

water travels downward to become part of

an a%uifer.

Rechar#e +ones are environmentall

sensitive areas because an pollution inthe rechar#e +one can also enter the

a%uifer.


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The Rechar-e /one


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The Rechar-e /one

!he si+e of an a%uifer's rechar#e +one is affected b the!ereabilityof the surface above the a%uifer.

Structures such as buildin-s and !ar)in- lots can act

as impermeable laers and reduce the amount of water

enterin# an a%uifer.

Communities should carefull mana#e rechar#e +ones,

because surface water can ta"e a ver lon# time to refill

an a%uifer, even tens of thousands of ears.


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Wells

) hole that is du- or drilled toreach #roundwater is called a well.

Humans have du# wells to reach

#roundwater for thousands of ears.

We di# wells because #round water

ma be a more reliable source of

water than surface water and

because water is filtered andpurified as it travels under#round.


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!he hei#ht of the water table chan#es seasonall, sowells are drilled to e0tendbelow the water table.

&f the water tables falls below the bottom of the welldurin# a drou#ht, the well will dr up.

&n addition, if #roundwater is removed faster than it isrechar#ed, the water table ma fall below the bottom of awell.

!o continue supplin# water, the well must be drilleddeeper.

Wells


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Tic)et out the Door

1. What is the difference between fresh and salt water/

0. What is the percenta#e of Earth that is covered with

water/

. What is a river sstem/

2. What is #roundwater/

3. What is an a%uifer/

4. What is the difference between permeabilit and

porosit/

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Ch11 Sec1 Revised