DK See for Yourself Water

8/12/2019 DK See for Yourself Water

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See for yourself

H2O, NEUTRAL, LIQUID

atmosphere, steam, ice, flood

cloud, ocean, tide, river, life

science all around you





Written by Trevor DaySeries Consultant Dr Jon Woodcock

water



Senior editor Fran JonesSenior art editors Smiljka Surla, Jacqui SwanEditors Samone Bos, Sue Malyan, Andrea MillsArt editors Sheila Collins, Phil LetsuManaging editor Linda EspositoManaging art editor Diane ThistlethwaitePublishing manager Andrew MacintyreCategory publisher Laura Buller Design development manager Sophia M Tampakopoulos

Picture research Liz MooreDK picture library Claire BowersProduction controller Erica RosenDTP designer Andy Hilliard Jacket editor Mariza O'Keeffe Jacket designers Jacqui Swan, Smiljka Surla

Illustrations Dave Cockburn

First published in Great Britain in 2007 byDorling Kindersley Limited,80 Strand,London WC2R 0RL

Copyright © 2007 Dorling Kindersley Limited, LondonA Penguin Company

2 4 6 8 10 9 7 5 3 1TDA043 – 12/06

All rights reserved. No part of this publication may be reproduced,stored in a retrieval system, or transmitted in any form or by anymeans, electronic, mechanical, photocopying, recording orotherwise, without the prior written permission of the copyrightowner. A CIP catalogue record for this book is available fromthe British Library.

ISBN: 978-1-40531-874-7

Jacket colour reproduction by Colourscan, SingaporeInside colour reproduction by Wyndeham pre-press, London

Printed and bound in China by Hung Hing

Discover more at www.dk.com

LONDON, NEW YORK, MELBOURNE,MUNICH, AND DELHI



Wet stuff (H2O)

Water world

Salty or fresh

Frozen water

Water and plantsLife in water

Still waters

Rivers

Oceans

Tides and currents

Shaping the land

Weather

Clouds

Water cycle

On the move

Body water Water power

Under the ground

Urban water

Rural water

Water and industryDirty water

Flood and drought

Global warming

The future

Facts and figures

Timeline

Glossary

Index

4

6

8

10

1214

16

18

20

22

24

26

28

30

31

36

38

40

42

44

4648

50

52

54

56

58

60

62



Water is the most common – and most remarkable –substance on Earth’s surface. It is also the only

matter that is naturally abundant as a solid,a liquid, and a gas. The smallest amount ofwater that exists is a water molecule, which ismade up of two atoms of hydrogen (H

2) and one

of oxygen (O) bonded tightly together. A drop

of water contains more than one billion,billion water molecules.

Water as a solidWhen water freezes, its molecules

slow down and huddle together. Eachmolecule links with four others and pullsinto an arrangement of interconnected rings.Ice is hard because the water molecules arelocked into this crystal pattern.

Water as a gasIn steam, the water

molecules have too muchenergy and move too quicklyfor electrical attractions to hold themtogether. So steam has no shape – it justexpands to fill the available space.

Water as a liquidIn liquid water, the water

molecules are only looselyconnected by electrical attractions, andthe molecules are free to move around. This iswhy liquid water flows easily when poured andtakes on the shape of its container.

Sticky moleculesThe hydrogen atoms in a water molecule areslightly positively charged electrically and theoxygen atom is slightly negative. Opposite chargesattract, so water molecules tend to “stick” together.

Surface tensionWhen water molecules stick together

across the surface of water, they form a“skin” on the water. This effect is called

surface tension. Water’s surface tensioncan support the weight of insects,

such as this pond skater.

H

H

O

–

+

4

+



5

Universal solvent Sugar, salt, andsoluble aspirin are

just a few of the thingsthat dissolve in water.In fact, more chemicals

dissolve in water thanin any other liquid. This

is because the electricalcharges on water molecules

attract the atoms from othersubstances. This pulls the substances

apart and drags them into a solution.

Water and gravityThis water drop isbeing pulled off a leaf bygravity. As the drop falls,

it will become almostspherical in shape. Then airpushing against it will squash itinto a bun shape, or it might splitinto several droplets.

Water in spaceThe electrical forces

between watermolecules naturally

pull them inwards toform spheres. In

space there is hardlyany gravity, so waterdrops float. Here, an

astronaut is visiblethrough a perfectly

spherical drop of water,which is acting as a lens.

ExpandsFreezes

Boils

Water facts

At sea level, pure waterwill freeze at a temperatureof 0°C (32°F).

At sea level, pure waterwill boil at a temperatureof 100°C (212°F).

Water is unusual becauseit expands when it freezes.Other liquids get smaller.

ImpureFreshIf water has salt dissolved in it,then it has a lower freezing pointand a higher boiling point.

Pure water in a glass tumblerhas no smell, no colour, andno taste.

Water dissolves substances well,so when it flows through soil orrock, chemicals get picked up.

AltitudeMeltsBurning produces water. Whenmost substances burn in air,they release steam.

When ice melts, it absorbs heatenergy. This is why ice is goodfor cooling drinks.

At high altitude, pure waterboils at the lower temperatureof 86°C (186°F).

Salty

Burns



Absorbing light Sunlight contains all the colours of the

rainbow, but water absorbs some coloursof light more than others. Water absorbs

colours at the red end of the spectrummuch better than those at the blue-greenend, which penetrate much deeper.

6

The blue planet In photos taken from space, the Earth appearsmostly blue, because of the huge areas ofocean. The white swirls are clouds containingwater in the form of droplets and ice crystals.

The first oceansScientists think that thefirst oceans formednearly 4 billion yearsago. The ocean waterprobably came from

steam, which wasreleased by eruptingvolcanoes. The steamcooled and turnedto water in theatmosphere, then fellto Earth as rain. Thiscollected in low-lyingareas to create oceans.

5 m(16 ft)

10 m(32 ft)

100 m(326 ft)

Planet Earth is a watery place, with more than 70 per cent of its surface coveredin seawater. Most of this water is found in five oceans – giant hollows that have

filled with salty water. Of the remaining surface water, most is locked up in icearound the North and South Poles. The water in lakes, rivers, clouds, soils, andliving organisms is small by comparison, but very important.

Why is the sea blue?Water is slightly blue, but this is only

obvious when you see it in largeamounts, and when the water

is not stained by particles,such as sand or mud.

Clear seawater in brightsunshine, as around this

coral atoll, looks a richblue because the

water has absorbedother colours in

the light.

Light underwater Even the most beautiful, multi-coloured coral reefs can look

quite drab underwater. Everything looks very blue-greenbecause the water filters out red and yellow light.

However, if you shine a beam of white light underwaterthe full range of colours is magically revealed.

Light penetration

0

D e p t h o

f o c e a

n





OceansThe oceans are salty becausethe water in them is constantlyevaporating into the air, leavingsalts behind. Some inlandlakes have no outflows andcan become salty too.

EstuariesThe place where a river meetsthe sea is called an estuary. Here,fresh water and seawater mix.Water in estuaries is brackish –saltier than fresh water, but notas salty as seawater.

Anyone who has swallowed seawater while swimmingknows it tastes salty. In fact, most of the liquid water on

Earth’s surface lies in the oceans. The salt, called sodiumchloride, comes from soil and rocks on the land. Over

millions of years, rivers have gradually washed this salt intothe sea. Fresh water is found in most lakes and rivers, locked

up as ice, and in the atmosphere. It contains very little

dissolved salt. Seawater is not safe for people to drink,but fresh water – providing it lacks harmful

chemicals or microbes – is safe to swallow.

8

Fresh water At the start of a river, the freshwater it contains is usually cleanand clear. As it gradually flowsthrough the landscape, the riverpicks up more sediment anddissolved substances.

Staying afloat An object’s ability to float in water is knownas buoyancy. Water provides morebuoyancy when it contains dissolved salt orother substances. The symbol above, called aPlimsoll line, is used on cargo ships and marksthe level to which the ship can be safely loaded.The maximum load in seawater (T) would causethe ship to sink a bit lower if it sailed into freshwater (F). Warm water provides even less buoyancyso the boat would sink further (TF).

TF Tropical fresh water

F Fresh water

T Tropical seawater

S Summer (temperate) seawater

W Winter (temperate) seawater



9

Salty lakeThe Dead Sea is a lake betweenIsrael and Jordan. It contains theworld’s saltiest water – ninetimes saltier than seawater.Swimmers in the Dead Sea arevery buoyant and float easily.

Valuable salt Here in Vietnam, the Sun’sheat is being used to evaporatethe water from seawater inartificial ponds. Salt from theseawater is left behind andpeople gather it up to sell.

pH scaleAcids and alkalis

are chemicals thatcan cause strong

reactions. Strong acidsand alkalis can “burn”

skin. The pH scale is usedto show how strong an acid

or alkali is. Pure water isneutral – neither acid nor alkali.

It lies in the middle of the scalewith a pH of 7.

Salt of the EarthIf all the water in the oceans evaporated,and the salt that remained was piled ontothe land, it would form a layer more than

120 m (400 ft) deep. This is so muchsalt that it could cover the land with saltbuildings that averaged 30 storeys high.

Battery acid,sulphuric acid

Ammonia,household cleaners

Soap

Orange juice,fizzy drinks, wine

Bananas,black coffee

Laundry bleach

Baking soda

Milk of magnesia,

detergents

Seawater, eggs

Pure water,blood

Acid rain,tomatoes, beer

Lemon juice,vinegar

Rainwater,milk, urine

Strong drain bleach

p H S C A L E

E x t r e m e l y a c

i d i c

N e u t r a l

E x t r e m e l y

a l k a l i n e

1

2

3

4

5

6

7

0

8

9

10

11

12

13

14



Ice forms in the coldest parts of the planet – especially around

the North and South Poles and on mountain peaks. As we seefrom ice cubes in a glass, ice floats on water. If it didn’t, the

polar oceans would freeze solid, from the bottom up. The iceon top acts like a blanket, slowing the cooling of the water

below. More than three-quarters of all fresh water on Earth’ssurface is ice – about half lying on the land and the other

half floating on the sea.

Why ice floatsWhen water gets closeto freezing point, the

molecules in it moveslightly further apartas they start to formcrystals. As a result,freezing water contains

fewer molecules thanwarmer water, so it is

lighter. This is why ice andnear-frozen water always

float on top of warmer water.

Iceberg An iceberg is

a giant chunk offreshwater ice that

has broken away from aglacier or ice sheet and

floated out to sea. This

process of breaking awayis called calving. In a typicaliceberg, less than 20 per centof the ice can be seen abovethe surface of the water.



O p e n p o r e

L e a v e s h a v e p o

r e s c a l l e d

s t o m a t a ( s i n g u l a r s t o m a ) o n

t h e i r u n d e r s i d e

. T h e y

o p e n a n d c l o s e

t o

c o n t r o l t h e l o s s

o f w a t e r

f r o m t h e l e a f . T h e s t o m a

s h o w n h e r e i s o p e n .

T h i s a l l o w s t h e

g a s

c a r b o n d i o x i d e ,

w h i c h t h e p l a n t n e e d s f o r

p h o t o s y n t h e s i s

, t o e n t e r t h e l e a f f r o m

t h e a i r . A t t h e s a m e t i m e ,

w a t e r e x i t s t h e

l e a f t h r o u g h t h e p o r e .

T r e e

o f l i f e

D u r i n g

t h e w e t s e a s o n ,

t h i s

b a o b a b t r e e i n A f r i c a s t o r e s w a t e r

t o h e l p i t s u r v i v e t h e d r y

s e a s o n .

S p o n g y fi b e r s

i n s i d e t h e t r e e ’ s t r u n k s w e l l u p t o s t o r e m o r e

t h a n 2 6 , 0

0 0 g a l ( 1 0 0

, 0 0 0 l i t e r s ) o f w a t e r ,

w h i c h l o c a l s c a n u s e

i f t h e r e i s a d r o u g h t .

L e a f f a c t o r

T h i s s e c t i o n t h r

o u g h t h e t o p o f

a l e a f s h o w s a g

r o u p o f h i g h l y

m a g n i fi e d c e l l s .

T h e fl a t t e n e d c e l l s

a t t h e t o p h a v e

a w a x y c o a t i n g o n

t h e i r u p p e r s u r f a c e ,

w h i c h

p r e v e n t s w a t e r

f r o m e s c a p i n g .

P h o t o s y n t h e s i s

o c c u r s i n s i d e

s t r u c t u r e s c a l l e d c h l o r o p l a s t s .

T h e s e a r e s h o w

n a s f a l s e - c o l o r e d

g r e e n b l o b s i n s

i d e t h e l o n g c e l l s .

S o l i d w o o d

T h e w o o d i n

s i d e a t r e e t r u n k i s m a d e o f

t h o u s a n d s o

f w a t e r - t r a n s p o r t i n g v e s s e l s .

T h e w a l l s o f t h e s e v e s s e l s a r e l i n e d w i t h

a t o u g h s u b s t a n c e c a l l e d l i g n i n ,

w h i c h

g i v e s w o o d i t s i m m e n s e s t r e n g t h .

E a c h

t r e e “ r i n g ” r e

p r e s e n t s a y e a r ’ s g r o w t h .

I n l e a v e s , w a t e r i s u s e d t o

m a n u f a c t u r e f o o d u s i n g

s u n l i g h t ( p h o t o s y n t h e s i s ) .

W a t e r e v a p o r a t e s i n t o

t h e a i r f r o m p o r e s o n

t h e b o t t o m o f l e a v e s .



R o o t h a i r s

S m a l l e r r o o t s , s

u c h a s t h e o n e s o n

t h e s e s e e d l i n g s

, a r e c o v e r e d w i t h

h u n d r e d s o f t i n

y o u t g r o w t h s c a l l e d

r o o t h a i r s . T h e y c r e a t e a h u g e

s u r f a c e a r e a f o r a b s o r b i n g w a t e r .

E a c h r o o t h a i r i s o n l y a b o u t

0 . 0

0 3 i n ( 0 . 1 m

m ) w i d e a n d i s

c o v e r e d i n a s i n g l e l a y e r o f c e l l s s o

t h a t i t c a n s w i f t l y t a k e u p w a t e r a n d

n u t r i e n t s f r o m t h e s o i l .

W a t e r t r a n s

p o r t e r

T h e i n s i d e o f a

p l a n t s t e m i s p a c k e d

w i t h t h o u s a n d s

o f t i n y t u b e s c a l l e d

v e s s e l s . T h e y a r e m a d e f r o m c e l l s

t h a t c o n n e c t e n

d t o e n d t h e n d i e ,

l e a v i n g a h o l l o w

t u b e .

I n t h e s e t h i n

t u b e s , s u r f a c e t e n s i o n w o r k s t o

p u l l w a t e r u p t h

e s t e m .

T h i s i s

k n o w n a s c a p i l l a r y a c t i o n .

M i c r o s c o p i c v e s s

e l s

i n t h e s t e m t r a n s p o r t

w a t e r u p t o t h e l e

a v e s .

T r a n s p i r a t i o n

W a t e r e v a p o r a t e s f r o m

t h e s u r f a c e

o f c e l l s i n s i d e l e a v e s a

n d p a s s e s o u t t h r o u g h

p o r e s i n t o t h e a i r . T h i s l o s s o f w a t e r i s c a l l e d

t r a n s p i r a t i o n .

T h e p r o

c e s s h e l p s t h e p l a n t b y

“ p u l l i n g ” w a t e r a n d n

u t r i e n t s t h r o u g h i t .

H o w e v e r , i f t r a n s p i r e

d w a t e r c a n n o t b e

r e p l a c e d w i t h m o r e

w a t e r f r o m t h e s o i l ,

t h e p l a n t s o o n w i l t s .

13

T h e m a i n r o o t

c a r r i e s w a t e r u p

i n t o t h e s t e m .

S m a l l r o o t s t a k e u p

w a t e r a n d n u t r i e n t s

f r o m t h e s o i l .

P l a n t s o p e

r a t e l i k e m i n i - f a c t o r i e s ,

c a r r y i n g o u t a l l k i n d s

o f p r o c e s s

e s — a n d t h e y n e e d w a t e r f o r a l l o f t h e m .

W a t e r t r a n

s p o r t s s u b s t a n c e s a r o u n d t h e p l a n t , i n t h e

s a m e w a y

t h a t b l o o d m o v e s t h r o u g h a p e r s o n ’ s b o d y .

A l l t h e p l a n t ’ s c h e m i c a l r e a c t i o n s

, s u c h a s m a k i n g f o o d

u s i n g s u n l i g h t ( p h o t o s y n t h e s i s ) , t a k e p l a c e i n w a t e r . T h i s

w a t e r i s a b

s o r b e d f r o m t h e g r o u n d t h r o u g h t h e r o o t s a n d

m a k e s u p a t l e a s t 8 0 p e r c e n t o f e v e r y p l a n t . W a t e r p r e s

s u r e

k e e p s t h e

p l a n t ’ s s t e m a n d l e a v e s w e l l s u p p o r t e d .



SnowflakesWhen the air is cold, ice

crystals grow aroundspecks of dust inside

clouds to form snowflakes.

When they are large andheavy enough, the flakes fall.Each snowflake contains 50 ormore ice crystals, arranged in a

unique six-sided pattern.No two are identical.

Grease iceIn winter, the seawater in the

polar regions freezes, creatingvast areas of ice. When sea icebegins to form, ice crystalsgather at the sea surface.The winds and waves keep these

crystals in small clumps. This thinice looks like fat floating on thesea and is called grease ice.

Pancake iceAs grease ice thickens and isshaped by the wind and waves,

it breaks up into “pancakes” of ice

with turned-up edges. Ice crystalstrap little or no salt, so the saltfrom the seawater is pushed into

channels inside the ice andeventually trickles out. This

makes the seawater underthe ice even saltier.

Sea-ice sheetsPancake ice usually freezes

to form a continuous sheetof ice, which is about 1 m

(3 ft) thick in its first year.Each winter, huge sheets of

sea ice grow southwardsin the Arctic Ocean and

northwards in the SouthernOcean around Antarctica.

Ice floesSheets of sea ice up to 10 km(6 miles) across are called floes;larger sheets of ice are knownas ice fields. Many of the floesbreak up during the summer

months when the weatherwarms up. Winds, waves, andcurrents make the floes jostle

about and help to break themup more quickly.

Slippery as iceThis skater is actually skating

on a thin layer of liquid water, just a few molecules thick,

which forms on top of the iceunder the blades of his skates.When he moves on, the liquid

layer instantly freezes back into ice.Scientists still disagree about exactlyhow this layer forms.

Evidence from the iceAn ice core is a column of ice drilled out ofa glacier or an ice sheet. The ice containsair and particles of dust and pollen thatwere trapped in it hundreds, or thousands,

of years ago. When analyzed, the airreveals the balance of gases in theatmosphere at that time. The dust and

pollen give scientists valuable clues aboutthe climate long ago.

11



14

Scientists think that the first life forms may haveevolved at the edges of the oceans more than

3.5 billion years ago. Today, most waterteems with life, from microscopic planktonto the largest whale. For each, the wateraffects its shape and how it lives. Aswater is hundreds of times heavier andthicker than air, it supports organismsmore readily than air does. However,

water offers more resistance tomovement, so large marine animalshave a streamlined shape to helpthem slip easily through water.

Animal planktonThis is the skeleton of a radiolarian, atiny animal plankton (zooplankton).It eats smaller organisms, such as

coccolithophorids. The spikesenlarge its surface area and

increase friction with the water,

which helps it to float. Manytypes of radiolarian contain oil

droplets or air bubbles thathelp them stay afloat.

Plant planktonThese rings are chalky plates in the skeleton of

a coccolithophorid. This minute organism is a typeof plant plankton (phytoplankton) and is 10 times

smaller than a full stop. Being so tiny, it sinks veryslowly and does not have to swim hard to stay afloat

near the water surface.

Algal bloomsThere are so many phytoplankton in the sea thatthey can form great green patches, called algal blooms.The turquoise areas here are phytoplankton in theNorth Sea, off Scandinavia. These populations performthe same function that forests do on land. They take incarbon dioxide and give out oxygen in the process of

photosynthesis, refreshing the Earth’s atmosphere.



Breathing underwater This axolotl is a salamander that lives in Lake Xochimilico in

Mexico. Like many water-living animals, it absorbs oxygenfrom the water through its pink, feathery gills. Gills foldoutwards. If they folded inwards, like our lungs, they wouldquickly become clogged with stagnant water.

Bony fishThese fast-swimming

tuna are highlystreamlined to help them

cut through the water. A tunabreathes in water and takesoxygen from it using its gills,

which are hidden behind a flap ateach side of its head. An air sacinside its body buoys the fish up.

Tuna find prey using sensitive cellsalong the flanks that detect

vibrations in the water.

Cartilaginous fishWith a skeleton of light cartilage(gristle) rather than heavy bone,

and an oil-filled liver, a shark is wellbuoyed up in the water. Sharks havea very keen sense of smell and can

detect one drop of blood in aswimming pool full of water.

Special jelly-filled pores on the

shark’s snout enable it tolocate prey by sensing theirelectrical fields.

Marine mammalAlthough they look like fish,whales are mammals. They

have lungs and must come tothe surface regularly to breathe

air. Even a large whale has athin skeleton because the water

supports its body. If a whale

became stranded on the shore,the unsupported weight of its bodycould crush its internal organs and it

would be unlikely to survive.



16

Tree poolIn rainforests, pools

containing only a smallamount of water oftenform where bromeliad

plants grow on the trunks andbranches of trees. Thesepools teem with all kinds

of life, from plantand animal planktonto predators aslarge as frogs.

Ponds and lakes are like giant puddles, with lakes largerthan ponds. Most are fed by fresh water that runsoff the surrounding land, or flows into themfrom rivers. Ponds and lakes are unique,because they contain water that is stillrather than flowing. Lakes usually exist

for hundreds or thousands of years.This seems like a long time to us, butcompared to oceans and most rivers,lakes are short lived. Over the years,particles of sediment start to settle in alake, eventually filling it so it dries out.

The largest of the five North American Great Lakes,Superior is also the world’s largest lake by area.

Important lakes

BaikalThis Russian lake is the deepest in theworld and the largest lake by volume.

Constance Lying between Switzerland, Germany, and Austria,Lake Constance supplies water to 4.5 million people.

Superior Titicaca At an altitude of 3,812 m (12,516 ft),Titicaca is the highest big lake in the world.

WetlandsSwamps and other areas where the soilis waterlogged are known as wetlands.These areas are crucial water stores thatsupply water to rivers. Plants andmicrobes remove harmful substances

from the water as it passes throughthe wetlands.



Invaded by reedsWhen a lake starts to fill with sediment, reeds growaround its edges and the area of open water shrinks.Eventually, land plants grow where there were oncereeds, and what was once a lake becomes anarea of land.

Seasonal poolVernal pools fill with water in the wet season and turnto parched ground in the dry. When the rains return,dormant eggs hatch out and young (larvae) changeform. The pond is soon bursting with brine shrimpand tadpole shrimp.

Giant lakesThe biggest lakes are like inland seas. At 25 millionyears old, Lake Baikal in Russia is the world’s mostancient lake. Unusually, it has not silted up becauseground movement is causing its bedrock to sink asfast as sediment is added.

Victoria The world’s second largest lake by area isLake Victoria in Africa.

18



Most rivers begin life as a tiny stream running down a mountain slope. They arefed by melting snow and ice, or by rainwater running off the land. The waterfollows cracks and folds in the rock as it flows downhill. Streams meet and jointogether, growing larger and larger until the flow can be called a river. When theriver reaches lower ground, it usually slows, widens, and takes a winding route.Eventually, most rivers empty into the sea.

V-shaped valleyHigh in the mountains, the river isnarrow and fast flowing. Its watercarries pebbles and boulders thaterode the sides and bottom of theriverbed, cutting a V-shaped valley.

Meltwater A stream fed by melted ice, ormeltwater, shrinks and expands withthe seasons. The stream gushes overits rocky bed in spring, but in wintermay be reduced to just a trickle.

WaterfallFast-flowing water in a river’s upperreaches can carve out waterfalls. If theriverbed changes abruptly from hard tosoft rock, the river erodes the softerrock. This leaves a steep cliff of hardrock, which becomes a waterfall. Rapids

If a river flows over a bed of variedrocks, the softer rocks are worn away,leaving hard rocks poking up throughthe water. The water swirls aroundthese obstacles, creating rapids.

Indus Fed by snow in the Himalayas, the Induseventually flows into the Arabian Sea.

Swift This meltwater-fed river in Alaska, USA, shifts itscourse through the mountains from year to year.

Victoria Falls Mekong Along the border of Thailand and Laos, theMekong flows though spectacular rapids.

The rivers featured

These 108-m- (355-ft-) high falls on the Zambezi areknown as “Mosi-oa-tunya”, the smoke that thunders.

18



m

w n

y os h e n

te

s



T h

e o c e a n s a r e u n i m a g i n

a b l y v a s t . T o g e t h e r , t h

e y m a k e u p m o r e t h a n

9 5

p e r c e n t o f E a r t h ’ s l i v i n g s p a c e .

T h e d e e p e s t p a r t s o f t h e o c e a n

d e

s c e n d t o m o r e t h a n 1 0 k m ( a

b o u t 6 m i l e s ) a n d t h e c o l d ,

d a r k ,

h i g h - p r e s s u r e e n v i r o n m e n t a t t h e b o t t o m i s

v e r y d i f f e r e n t f r o m t h

e

c o

n d i t i o n s a t t h e s u r f a c e

. F i s h a n d o t h e r m a r i n e a n i m a l s h a v e e v o l v e d

b o

d y s h a p e s a n d h u n t i n g t e c h n i q u e s t h a t e n a b

l e t h e m

t o

s u r v i v e a t a p a r t i c u l a r

l e v e l .

T w i l i g h t z o n e

A t d e p t h s b e t w e e n 2 0 0 m

( 6 5 0 f t ) a n d 1 , 0

0 0 m

( 3 , 3

0 0 f t ) o n l y s p a r s e

s u n l i g h t p e n e t r a t e s . I n

t h i s t w i l i g h t w o r l d s o m e

c r e a t u r e s m a k e t h e i r o w

l i g h t ( b i o l u m i n e s c e n c e )

t o a t t r a c t p r e y ,

c o n f u s e

p r e d a t o r s , o r t o i d e n t i f y

e a c h o t h e r . M a n y

c r e a t u r e s r i s e c l o s e r t o

t h e s u r f a c e a t n i g h t t o

f e e d o n p l a n k t o n

( d r i f t i n g o r g a n i s m s ) .

C o r a l r e e f s

T

h e s e r o c k y s t r u c t u r e s

g

r o w i n w a r m ,

c l e a r ,

u

n p o l l u t e d s h a l l o w w a t e r .

T h e y a r e b u i l t b y c o r a l

p

o l y p s – m i n i a t u r e a n i m a l s

t h

a t a r e r e l a t e d t o s e a

a n e m o n e s a n d j e l l y fi s h .

A

b o u t o n e - t h i r d o f t h e

o c e a n ’ s a n i m a l a n d p l a n t

s p e c i e s l i v e s a m o n g t h e

n o o k s a n d c r a n n i e s o f

c o r a l r e e f s .

S

u n l i t z o n e

T h e s u n l i t z o n e l i e s i n t h e

u

p p e r 2 0 0 m ( 6

5 0 f t ) o f t h

s e a w h e r e t h e r e i s s u f fi c i e n

l i g h t f o r m a r i n e p l a n t s t o

p

h o t o s y n t h e s i z e ( m a k e

f o o d u s i n g l i g h t e n e r g y ) .

T

h e s u n l i t z o n e c o n t a i n s

m

o s t o f t h e s e a ’ s c r e a t u r e

t h a t a r e f a m i l i a r t o u s .

M a r i n e t u r t l e

T h e

e i g h t s p e c i e s o f m a r i n e

t u r t l e a r e a i r - b r e a t h i n g

r e p

t i l e s .

T h e i r v a r i e d d i e t

i n c l u d e s j e l l y fi s h .

F e m a l e s

d i g

n e s t s o n s a n d y b e a c h e s

i n w

h i c h t o l a y t h e i r e g g s .

J e l l y fi s h

T h e s e a

r e i n v e r t e b r a t e s

( a n i m a l s w i t h o u t b a c k b o n e s ) .

M o s t s w i m s

l u g g i s h l y i n t h e

s u r f a c e

w a t e r s .

T h e y u s e

s t i n g i n g t e n t a c l e s t o c a p t u r e

s m a l l e r

a n i m a l s .

M a r l i n

T h e m a r l i n h u n t s fi s h a t h i g h

s p e e d u s i n g i t s s w o r d - l i k e

u p p e r j a w t o s w i p e a n d d i s a b l e

p r e y .

I t i s t h e w o r l d ’ s f a s t e s t

fi s h w i t h s p e e d s o f m o r e t h a

n

1 1 0 k m / h ( 6 8 m p h ) .

V i p e

r fi s h

T h i s

fi s h h a s a l a r g e

m o u

t h a r m e d w i t h

l o n g

c u r v e d f a n g s .

A v i p e r fi s h w i g g l e s a

s p i n

e o n i t s d o r s a l fi n

t o a t t r a c t p r e y c l o s e t o

i t s fi

e r c e s o m e m o u t h .

L a n t e r n fi s h

L a r g

e e y e s h e l p l a n t e r n fi s h t o

l o c a

t e a n i m a l p l a n k t o n p r e y .

T h e

l i g h t - e m i t t i n g p a t c h e s

o n t h e h e a d ,

fl a n k s ,

a n d

u n d

e r s i d e h e l p t h e m t o

r e c o g n i z e o t h e r m e m b e r s

o f t h e i r s p e c i e s .

S p e r m w

h a l e

T h i s w h a l e ,

a n a i r - b r e a t h i n g

m a m m a l , c a n r e a c h u p t o

1 8 m ( 6

0 f t ) l o n g .

S o m e a d u l t s

m a k e a m a z i n g l y d e e p d i v e s

i n t o t h e t w i l i g h t a n d d a r k

z o n e s i n s e a r c h o f s q u i d .

Scuba diver can go downto depths of up to 282 m(925 ft).

s t v e s

ln h i l l y

h e

h t

w n

m e s

d s

m t o



D a r k z o n e

N o s u n l i g h t r e a c h e s

t h e o c e a n d e p t h s

b e y o n d a b o u t

1 , 0

0 0 m ( 3 , 3

0 0 f t ) .

T h e o n l y l i g h t i s t h a t

p r o d u c e d b y t h e

o r g a n i s m s t h e m s e l v

o r b y t h e o c c a s i o n a

g l o w o f v o l c a n i c

a c t i v i t y . T h e w a t e r i n

t h e d a r k z o n e i s a c h

0 – 4 ° C ( 3 2 – 3 9 ° F ) . T h

p r e s s u r e o f t h e w e i g h

o f w a t e r p r e s s i n g d o w

i s m o r e t h a n 1 0 0 t i m

t h a t a t t h e s u r f a c e .

O

c e a n f l o o r

T h e b o t t o m o

f t h e o c e a n

r e c e i v e s a s t e a d y “ r a i n f a l l ”

o f p a r t i c l e s f r o m t h

e w a t e r s

a b o

v e .

T h i s i n c l u d e s d e a d

o r g a n i s m s , t h e w a s t e f r o m

m a r i n e c r e a t u r e s , a n d a l l k i n d

o f p a r t i c l e s , f r o m m

u d a n d

s a n d

t o o b j e c t s d u m p e d f r o m

s h i p s

. M u c h o f t h e w o r l d ’ s

w a s t e

e v e n t u a l l y fi n d s i t s w a y t

t h e o c

e a n fl o o r .

A n g l e r fi s

h

I t g o t i t s n a m e f r o m t h

e

l u m i n o u s

l u r e o n a s t a l k o n

t o p o f t h e h e a d .

T h i s a t t r a c t s

u n s u s p e c t i n g p r e y s o c l o s e t o

t h e fi s h ’ s

m o u t h i t c a n b e

s n a p p e d

u p w i t h o u t a c h a s e .

G u l p e r e e l

T h i s e e l s w i m s s l o w l y ,

l y i n g

i n w a i t f o r p r e y .

F o o d i s

s c a r c e i n t h e d e e p o c e a n ,

s o

a l a r g e m o u t h a n d e x p a n d i n g

s t o m a c h e n s u r e s t h a t a l m o s t

a n y s i z e p r e y c a n b e c a p t u r e d .

S m o k e r s

S o m e v e n t s h a v e t a l l

c h i m n e y s ,

f o r m e d f r o m

m i n e r a l s t h a t s e t t l e o u t

w h e n h o t v e n t w a t e r

m e e t s s e a w a t e r . B l a c k

“ s m o k e ” i s f o r m e d a

s h o t

w a t e r e x i t s t h e c h i m n e y .

G i a n t s q u i d

C l o s e r e l a t i v e

o f o c t o p u s a n d

c u t t l e fi s h ,

t h i s s q u i d c a n g r o w

u p t o 1 8 m ( 6

0 f t ) l o n g – t h e

w o r l d ’ s l a r g e s t i n v e r t e b r a t e .

A s p e c i m e n w

a s fi l m e d f o r

t h e fi r s t t i m e

i n 2 0 0 4 .

S a b r e t o o t h fi s h

N a m e d b e c a u s e o f i t s c u r v e d

t e e t h ,

t h i s fi s h l o o k s u p w a r d s

t o s p o t p r e y s i l h o u e t t e d

a g a i n s t t h e l i g h t c o m i n g f r o m

a b o v e .

I t h a s a s t o m a c h t h a t

c a n e x p a n d t o a c c o m m o d a t e

p r e y e v e n l a r g e r t h a n i t s e l f .

Nautile – a submersible –can reach depths of up to6,000 m (19,685 ft).

Trieste – a bathyscaphe –can travel down to theseabed at depths of11,500 m (37,730 ft).

H y d r o t h e r m a l v e n t s

T h e s e a r e l i k e g e y s e r s o n

t h e s e a fl o o r t h a t s p e w o u t

h o t w a t e r . T h i s c h e m i c a l -

r i c h w a t e r p r o v i d e s e n e r g y

t o m i c r o b e s .

T h e y ,

i n t u r n ,

a r e f o o d f o r g i a n t w o r m s ,

c l a m s ,

a n d m u s s e l s .



The water in the oceans is constantly on the move. Thepull of the Moon drags water across the Earth’s surface,producing surges called tides. Winds blowing acrossEarth’s surface stir and steer seawater, creating flows ofwater called currents, and whipping up its surface to makewaves. And the Earth spinning on its axis turns the surgesand currents, a feature called the Coriolis effect.

Tidal bulgeThe Moon’s pull causes theocean tides. Water that is closestto the Moon is pulled outwards,creating a bulge. A similar bulgeappears on the opposite side of theEarth as here the water is furthest away

and only weakly attracted. Where the bulgelies it is high tide, and in places where waterhas been withdrawn it is low tide. Mostcoastal areas have two high tides and twolow tides each day as the Earth turns.

High tide occurs whereseawater bulges due to

the pull of the Moon.

Gravitational attractionLike all large, dense objects in space, theMoon pulls other objects towards it. This iscalled its gravitational attraction. As the Moonorbits the Earth, it pulls the water on Earth’ssurface towards it. This creates a bulge ofwater travelling around the Earth.

High tideThe Bay of Fundy in Canada funnels water toa narrow point where the world’s largest tidesoccur. During the biggest tides of the year,the difference in level between high water(shown here) and low water can be anastonishing 17 m (56 ft).

Low tide occurs wherewater has been pulledaway into the bulge.

12

6

39

23Earth’s spin causes mostThe warm Gulf Stream keepsthe climate in northwest ntic

D r i f t

ARCTIC



Ocean currentsCurrents near the surface ofthe oceans are caused bywinds, and by cold watersinking and warm waterrising. Cold surface currents(shown in blue) carry coolwater from the polestowards the Equator, whilewarm currents (red) carryheat from the Equatortowards the poles.

Earth s spin causes mostcurrents to flow in circular

patterns, called gyres.

Low tide Just over six hours later, it is low tide. Thewater has drawn away from the shore and theseabed is exposed. Shore creatures, such asworms that live in the mud and snails that liveamong the seaweed, must cope withdrastically changing conditions.

Island hopping Some plants producefloating seeds, whichcan travel on oceancurrents to faraway

destinations. Thiscoconut is sproutingon a beach that may

be hundreds, oreven thousands, of

kilometres (miles) away

from the palm tree onwhich it originally grew.

Waves at seaMost sea waves are

made by winddisturbing the water

surface. The strongerthe wind, and the

longer it blows in onedirection, the biggerthe waves it creates.The water beneath a

wave is not carriedalong, except when thewave reaches shallow

water and “breaks”.

the climate in northwestEurope unusually warm.

G u l f S

t r e a m

N o r t h A

t l a n t i c

H u m b

o l d

t C

u r r e

n t

W est W i n d D r i f t

K u r o s h

i o C

u r r e n t

12

6

39

B e n g u e

l a C

u r r e n t

B r a z i l C

u r r e

n t

C a l i f o r n

i a C u

r r e n t

W e s t A

u s t r

a l i

a n

C u r

r e n

t

ANTARCTIC

PacificOcean

AtlanticOcean

IndianOcean C

u r r e n t

E a s t A

u s t r a

l i a n

24 Cut by a river I th A i USA l f di t



Water is one of the most powerful forces scraping and shapingthe Earth’s surface. Whether in its liquid form or as ice, watercarves out valleys, wears away coastlines, and carriesparticles of rock down rivers and across oceans. If water

breaks rock down into particles where it stands, theprocess is called weathering. If water wears rockaway and carries its particles from one place toanother, the process is known as erosion.

Coastal erosionWhen a storm wave crashes against a rocky shore its force can beas strong as the thrust of the space shuttle’s main engines. Overthe years, the waves erode the edge of the land, opening upcracks, dislodging chunks of rock, and often creating a natural arch.

In northern Arizona, USA, layers of sediment,deposited on the bottom of ancient seas, have beenraised onto land by great forces underground. In thelast few million years, the mighty Colorado River hascut a 1.6-km (1-mile) deep valley, the Grand Canyon,through this plateau.



Pillars of weathered rock These strangely shaped pillars are known as hoodoos.Made of soft limestone rock, capped by harder rock, they

are shaped by frost and rain. In winter, frost and ice crackthe rocks. In warmer weather, rainwater, which is slightlyacidic, slowly dissolves the limestone and rounds thehoodoo’s edges to create this shape.

Rivers of snow and iceWhen snow and ice settle on high ground, gravity

gradually pulls them down along any valleys. This formsa flowing “river” of ice, called a glacier. The moving iceenters cracks in the rock, dislodges rocky chunks, andwears away the bottom and sides of the valley.

Ice and frost Rainwater or melting snow seep into cracksin any exposed rock. If this water freezes, itexpands and creates wedges of ice. Thesecan cause enormous damage, prising anycracks wider and splitting the rock.

Glacier depth Glacier loss

G l a c i e r f a c t s Ice age

About 18,000 years ago, atthe height of the last ice age,almost a third of all land wascovered by snow and ice.

Glacier speed

Chemical weathering This limestone carving of a bird ona French church has been wornaway by centuries of rainfall. The

acid in rainwater has dissolved thestone. In recent years, sulphurdioxide from power stationemissions and other air pollutantshave made rain much more acidic.

Biological weathering

Plants contain lots of water. Asthey grow, their expanding rootsand branches have the power tocrack open and dislodge rock.This disused temple in Cambodiais gradually being ripped apart byinvading trees.

A typical glacier creeps alongeven more slowly than a snail.It advances only about 10 m(33 ft) in a year.

Ice in a glacier can be 3,000 m(10,000 ft) deep. It may hide amaze of meltwater streams thatcarve through the ice.

At one time, there were 150glaciers in Glacier NationalPark in the USA, but now only27 remain.

26 Air moves in giant circuits,called cells. There are three



On a hot summer day or a wet winter night, when thereare high winds or snow storms, it is always the relationship

between air, water, and heat that is responsible.Ever-changing quantities of these three elements

produce the wide variety of weather systemsexperienced around the world. Our weather occurs

in the lowest part of the atmosphere, whichextends about 12 km (7 miles) above Earth.

Weather patterns Climate is the pattern of weather in a particular area

over many years. At the Equator, the weather is always

warm and often wet. Near the poles, conditions arecold and often dry. In between, weather conditions vary.But whatever the climate, it shapes the lives of local plants

and animals. The African savannah, shown here, has a hotclimate where rainfall is highly seasonal.

cells in each hemisphere. Thisis the north polar cell.

In this tropical cell,warm air is rising

near the Equator,

then flowing north.

Warm, moist air (shown red) rises,then starts to cool down. Cool air(shown blue) warms up as it sinks

towards the ground.

The cells distribute heat overthe globe. Overall, they carry

cold air away from the polesand warm air towards them.

Global air circulationWhen air warms up, its gas molecules

spread out and occupy more space.This makes warm air lighter, so it rises.

In cool air, the molecules huddle closertogether, and take up less space.

Cool air is heavier, so it sinks. The risingof warm air and sinking of cool air is

called convection. It helps to generatethe big circulations of air across the globe.

This cell lies over themid-latitude region. Itcarries warm air northover southern Europe.

Equator

Tropic of Cancer

Tropic of Capricorn

In this polar cell, cool air issinking over Antarctica. It flows

back towards the Equator at a lowerlevel, then warms slightly and rises again.

27Frontal systems

The rapid uplift Sheets of rainclouds graduallyf d i t d

COLD FRONT WARM FRONT



Frontal systemsAn air mass is a large chunk of air in thelower atmosphere. It could be warm or

cold, and wet or dry. An air mass is largelyresponsible for the weather on the ground below

it. Where two air masses meet, at places calledfronts, they bring changeable weather. If cold air

flows under warm air, it creates a cold front, and itproduces violent weather. Warm air flowing over

cold air creates a warm front, and brings steady rain.

A steady downpour Raindrops form when water vapour in rising air

changes from a gas to a liquid (condenses). This formstiny water droplets, which gradually join together tomake raindrops. The uplift that makes air rise and create

rain clouds can occur where water or moist land warmsup, where winds collide, at fronts, or where moving air is

forced upwards to pass over higher ground. A downpourcan unload 2–5 cm (0.8–2 in) of rain in a single hour.

Wild weatherHurricanes form above warm tropical seas, where water is evaporating

rapidly from the sea surface. The water condenses higher in theatmosphere, releasing heat. This creates great instability, with windsblowing at more than 119 km/h (74 mph) and storm clouds that drop

torrential rain. In 2005, Hurricane Katrina forced millions of people toevacuate the southeastern USA, and killed at least 1,300 people.

HailstonesPellets of ice that fall from

clouds are called hailstones.They form when ice crystals

rise and fall repeatedly insidestorm clouds. The hailstonesgradually accumulate more

and more ice, growing largeruntil they are heavy enough to

fall from the sky. In someplaces, hailstones the size

of tennis balls can fall.

Warm air slowly overrides acold air mass.

creates toweringclouds, often bringing

thunder and heavy showers.

Cold air undercuts a warm air mass,forcing it to rise sharply.

form, producing steadyrain or drizzle.

10



CumulusIf the sky is full of giant puffs of cotton balls,cumulus clouds have gathered. Meaning “heap” inLatin, cumulus clouds are seen mostly on sunny days.They form by the process of convection—the land warmsair that rises as “thermals,” which cool to form the cloud.

It is unusual to look up into a cloudless sky. Most of thetime, there are clouds floating high above us. They arethe result of moisture in the air condensing to form minutewater droplets or ice crystals. These droplets or crystalsare so tiny that they stay suspended in the air. But whengroups of droplets or crystals combine, they becomeheavier. At this point, water droplets fall to the ground asrain, while ice crystals fall as snow or hail.

NimbostratusClouds are named after their shape, their height inthe atmosphere (altitude), and other key features.In Latin, nimbus means “rain” and stratus means “layered,”so these are flat, layered rainclouds. Usually dark in color,nimbostratus clouds cause prolonged heavy rain.

Cloud formationA cumulus cloud starts life as a pocket of especially warm,

moist air. Being warmer than the surrounding air, it is alsolighter, so it starts to rise, like a helium balloon. This risingair, called a thermal, expands and cools as it gets higher.When its temperature reaches the dew point, it starts to

condense into liquid water droplets, which form the cloud.

10,000 ft (3,000 m)

0

A pocket of warm air breaksaway from the ground and

rises because it is lighter thanthe surrounding, cooler air.

Air rises as swirling bubble,expanding and cooling.

Air cooled to temperatureof surroundings, so no longerrises. This is the top of the cloud.

6,500 ft (2,000 m)

3,300 ft (1,000 m)

Air has cooled to dew point.Water condenses toform cloud droplets.

Cloud facts



CumulonimbusA thunderstorm is brewing when fullydeveloped cumulonimbus clouds gatherin the sky. These giant versions ofcumulus clouds can be 5 miles (8 km)in height. The biggest cumulonimbusclouds can create hurricanes andtornadoes in warmer parts of the world.

Cloudy groundMist and fog are simply clouds that form

at ground level. Fog is thicker than mistbecause it contains more water droplets.If visibility is less than 0.6 miles (1 km),

it is classed as fog. As the sun comes up,fog usually clears.

CirrusThese feathery, white clouds are aptly namedcirrus—the Latin for “wisp of hair.” Made up of icecrystals, cirrus clouds streak the sky at high altitude.A type of cirrus, called cirrus uncinus, are known asmares’ tails because the clouds resemble horses’ tails.

AltostratusThese clouds form a midheight gray layer higher thancumulus, but below cirrus, and can often cover vastsections of sky. Altostratus is made up of a mixtureof ice and water. When the layer is thin, a ghostlySun shines through.

90% Of water in the air comes from the oceans

1801 The year cloud forms were first classified

Contrail The cloudlike trail from an airplane’s exhaust

100Lightning flashes occur every single second

10 The number of basic cloud types

Cloud facts

Dew point The temperature at which

water vapor in the air beginsto condense and form dropletsis called the dew point. If water

vapor condenses directlyonto the ground, it forms dew.

30



EvaporationPrecipitation

Percolation

Groundwater flow

Precipitationis the word used todescribe the different

forms of water that fall orsettle from the sky. Thisincludes rain, snow, sleet (icyrain), hail (ice pellets), frost, anddew. Precipitation is how water inthe air returns to Earth’s surface.

Percolationis the movement ofwater through soiland rocks as groundwater. It begins withinfiltration – watersoaking into the

ground. Water can take

from hours to thousandsof years to gather in

water-supplying layers of rockunderground, called aquifers.

Condensation

The world’s water circulates between sea, air,and land. As it moves, it often changes from



EvaporationTranspiration

Water vapour transport

Ocean

and land. As it moves, it often changes fromone state – solid, liquid, or gas – to another.The water cycle is powered by the Sun’s heat,which evaporates water from sea and land.Some of the moisture in the air then condenses

into water droplets or freezes into ice particles,which may fall as precipitation. Water gathers inrivers and lakes, and percolates through rockand soil, eventually moving downhill to the sea.

Runoff from the land

Condensationis the process of a gas

turning to a liquid, as seenin the dew on this spider’sweb. When air becomes

cold, its water vapour

separates out as droplets,which can form clouds.

When the droplets in cloudsmerge, they can becomeraindrops, large enough to

fall out of the sky.

Evaporationoccurs when molecules

of a liquid break free andbecome gas (steam).

Water evaporates all thetime from the sea, lakes,rivers, and wet surfaces

on land, such as a roof.This adds moisture tothe air, which travelsaround the planet on

winds and eventually fallsas precipitation.

Transpirationis the evaporation ofwater from plants.

By channellingwater through their

extensive system ofroots and leaves,plants make the

evaporation processfaster than evaporation

directly from the soil.Dense tropical forests release

so much water vapour thatthey become cloaked in mist.

31



In cities moist air gushes from officeair-conditioning systems and steambelches from car exhausts.

In towns water evaporates fromall wet surfaces including roofs andgardens. Steam enters the airthrough chimneys.

A hot shower usesabout 15 litres(4 gal) of water perminute. The usedwater goes downthe drain and into awastewater pipe.

A car wash uses atleast 120 litres (32 gal)of water per car. Theused water goes downthe drain and soonreaches a sewer.

Underground reservoir storeswater before it is distributed tohomes and businesses.

Washing line evaporation is greatest

on hot, dry, windy days.This is when water from

damp clothes evaporates

the fastest.

Waste from toilets isknown as foul waste and

is removed from homesvia pipes to a sewage plantfor treatment.

On Earth, there is a finite supply of water. It constantly moves around the planetin mini water cycles that may take hours or thousands of years to complete.

It travels through pipes, rivers, oceans, forests, deserts, rocks, animals, people,the food we eat, and the air that we breathe. It is even possible that oceancurrents still carry tiny amounts of Julius Caesar’s bathwater. This artworkshows the many ways water moves aroundan imaginary landscape.

Sewage plant treats waste water fromhomes and businesses to make it safe

to release into a river.

Acid rain occurs when chemicalsin the atmosphere mix with rain.



Crops are oftensupplied with riverwater through irrigationchannels. Some wateris lost by evaporationalong the way.

Brackish water from a desalinationplant may be used to grow salt-tolerant crops.

Wetlands, such as swamps, bogs, and marshesact like giant sponges that store water. They alsoclean the water and provide a habitat for wildlife.

Rivers receive water thatruns off the land. Most riversdischarge their water intothe sea.

In power stations some used water isreleased into the air through cooling

towers. Most is put back into rivers.

Many factories use water to

dissolve and dilute substances,wash products, and cool itemsduring their manufacture.

An estuary is where a riverempties into the sea and freshwater mixes with seawater.

Water treatment can take poor-quality waterand convert it into high-quality output.

A dam holds back water tostore it. A controlled flow ofwater through the dam cangenerate electricity.

Aircraft flying at highaltitudes can pick up froston their wings. They may

thi t di tThe Sun’s heat powers the

l b



Desalination plant removessalt from seawater, allowing

the water to be used forirrigation or even

for drinking.

The oceans hold 97 per centof the world’s surface water.Their heat and moisture,transferred to the air, fuelsthe world’s weather.

The iceberg that sankthe “Titanic” came from aGreenland ice sheet, whereit had lain for thousands ofyears. The collision released

water vapour into the air.

Breath of a blue whalecontains several litres (gal)of water. All air-breathinganimals lose water into the airthrough their breath.

Hurricanes develop in thetropics above warm seas.These giant storms cyclemillions of tonnes of water

each day.

Water evaporating from the seaaccounts for about 80 per cent oftotal evaporation.

Meltwater from thawing iceand snow in the mountainsfeeds many of the world’slargest rivers.

carry this vast distancesbefore it melts.

Clouds may form as air rises andits moisture condenses into waterdroplets or freezes into ice crystals.

water cycle by evaporatingwater and making it rise bymeans of convection.

Glaciers and ice sheetson land, and sea ice and

icebergs in the sea, containmost of the world’sfresh water.





Water weight Adult males are at least 60 per centwater, while adult females are at least50 per cent. Young babies are 70 per centwater and they become ill within a few

hours if the water they lose is notreplaced by drinking milk.

Blood Water content

Waterproof skinThe skin and its underlying tissue is the

largest organ in the body. It stays protected andwaterproof thanks to two substances – sebum and

keratin. Produced under the skin in the sebaceousglands, sebum is a natural oil that keeps the skin’s

outer layer, the epidermis, lubricated andwater-repellent. Also present is the

tough protein keratin, which acts as abarrier, preventing liquid from

entering the skin.

Water is essential to human life –it makes up more than halfyour body weight, is the maincomponent of each of your 100billion body cells, and without it, you

would die in just a few days. The amount of water insideyour body must remain almost constant for good health.

Losing even 10 per cent of your body weight in water isenough to make you seriously ill. The amount of waterleaving your body through sweating and weeing must bereplaced by regular drinking and eating. If the body’swater content drops, a part of the brain calledthe hypothalamus detects the change

and triggers the thirst response.

Muscle 83% 75%

Fat Bone

50%

60%

25% 22%

Blood armyThe blood flowing throughyour body consists of red and

hi bl d ll d d

37



white blood cells suspendedin a liquid called plasma, whichis 90 per cent water. As wellas transporting oxygen, food, andwastes, blood is also responsible forfighting disease and sealingdamaged skin.

Digestive juicesDuring a meal, these “pits”in the stomach lining pour0.5 litres (0.9 pt) of juice ontoyour food. This juice containsdigestive enzymes that break

down food. Deep in the intestines,digestive juices further break

down food. Almost all the waterfound in these juices is recovered

in the large intestine.

Working up a sweat Water leaves the body in four ways.About 1.5 litres (2.6 pt) of water aday exit the body in the form of

urine, 0.4 litre (0.7 pt) getsbreathed out, and about

0.1 litre (0.2 pt) is lost in solidwaste, or faeces. A further

0.5 litre (0.9 pt) of waterescapes through the skin as

sweat. By evaporating on theskin, sweat helps to coolus down. Exercise, stress,

and heat often increasesweat production.

Flexible jointsThe freedom to move easily comesfrom joints in the skeleton and the

muscles used to bend them. Boneswould grind together and wear away atthe joint without watery synovial fluid.This is secreted by a membrane tolubricate joints. The gaps on this X-ray ofa knee joint are full of synovial fluid.

38



Hydroelectric power The Grand Coulee dam on the Colorado River, USA is a barrier builtacross a valley to trap and temporarily store the moving water in ariver. As in other hydroelectric dams, water flows through tunnelsor tubes in the dam, turning propeller-like structures calledturbines. These generate electricity.

Water is heavy, there are vast amounts of it onEarth’s surface, and it can move with considerableforce. It has the power to do work, making it anexcellent source of energy. People use dams to

capture a river’s kinetic energy (energy of movement)and potential energy (such as energy released bya change in height). Hydroelectric dams convertwater’s energy into electrical power to supplyhomes, offices, and industry.

Power of the tidesIn some places, the tides can be harnessed to

generate electricity. This requires a big tidalsurge with a difference between water levels



Giant turbineThis is one of Grand Coulee’s

33 turbines being fitted. Wheninstalled, water flows past the

turbine blades, turning a shaftconnected to an electricitygenerator. The huge pressureof the water stored in thereservoir behind the dampushes water through theturbine blades at high speed.

Falkirk WheelScotland’s Falkirk Wheel is cleverly designed

to raise or lower barges to a height of 24 m(79 ft) using very little energy. When a barge

enters one of the wheel’s two containers,it pushes out an equal weight of water, so

the overall weight of the container doesnot change. The two containers are

counterbalanced, so as one rises, the otherdescends. Turning the wheel uses onlythe same amount of energy as

boiling eight kettles of water.

Indian dam protest Hydroelectric dams are a clean source

of energy and cheap to run. However,they can have huge disadvantages.

To build the reservoirs, it is necessary toflood large areas, often destroying

people’s homes. Changing the river’s flowcan also spread water-related diseases.These villagers in India are protesting

because a proposed dam will flood theirneighbourhood, forcing them to move.

surge, with a difference between water levelsat high and low tide of 7.5 m (25 ft) or more.

Modern tidal barrages work in a similarway to hydroelectric dams. Some are

two-directional, generating power from boththe rising and the falling tide. The Rance

Tidal Barrage in Brittany, northern France,operates in this way and supplies

electricity to more than 150,000 homes.

s e r s

c k f r o m d e e p

o u n d c a n r i s e

t o E a r t h ’ s

n d w a r m t h e

t h a t g a t h e r s

h i s c a u s e s

n d h o t w a t e r

a t r e g u l a r

t h r o u g h

s c a l l e d

a s s h o w n

o w s t o n e

r k , U S A .

40



W e l l i n g u p

I n s o m e p l a c e s , p e o p l e c a

n

d i g o r d r i l l a w e l l d o w n

t o t h e w a t e r t a b l e a n d

r e a c h s u p p l i e s o f f r e s h

w a t e r . M a n y w e l l s a r e

f e d b y a q u i f e r s –

l a y e r s

o f u n d e r g r o u n d r o c k s

t h r o u g h w h i c h w a t e r

m o v e s e a s i l y . I n m o s t

w e l l s , w a t e r h a s t o b e

p u m p e d t o t h e s u r f a c e ,

b u t

i n

a n a r t e s i a n w e l l , w a t e r r i s e s

n a t u r a l l y u n d e r p r e s s u r e .

G u s h i n g g e y

H o t m o l t e n r o c

u n d e r t h e g r o

q u i t e c l o s e

s u r f a c e a n

r a i n w a t e r

t h e r e .

T h

s t e a m a n

t o e r u p t a

i n t e r v a l s

o p e n i n g s

g e y s e r s , a

h e r e i n Y e l l

N a t i o n a l P a r

W a t e r t a b

l e

G r o u n d w a t e

r r i s e s t o a

l e v e l c a l l e d t h e w a t e r t a b l e .

B e l o w t h i s l e v e l , a n y s p a c e s

b e t w e e n t h e

r o c k a n d s o i l

p a r t i c l e s a r e f u l l o f w a t e r , s o t h e

g r o u n d i s s a t u r a t e d .

T h e w a t e r

t a b l e u s u a l l y

r i s e s a n d f a l l s w i t h

t h e s e a s o n s ,

g e t t i n g h i g h e r

d u r i n g t h e w e t s e a s o n a n d

l o w e r d u r i n g

t h e d r y s e a s o n .

T h e w a t e r s u

r f a c e o f r i v e r s a n d

l a k e s u s u a l l y

l i e s l e v e l w i t h t h e

w a t e r t a b l e .

W a t e r t a b l e

S u r f a c e

w a t e r

B e l o w t h e w a t e r t a b l e

w a t e r fi l l s t h e s p a c e s

b e t w e e n p a r t i c l e s .

U n s a t u r a t e d z o n e

S a t u r a t e d z o n e





Down the plugholeThe water that empties down the sink runs

to a main wastewater pipe that leaves thet Thi i t j i ith l



property. This, in turn, joins up with a largerpipe or underground channel called a sewer.Networks of sewers carry waste water, which

flows downhill under gravity or is pushed alongby pumps. Sewers receive all kinds of waste

water, including water that runs off the streetsand water from offices and factories.

Sewer robot Sewer pipes often run deep underground.

Workers enter sewers through vertical shaftsto inspect them for damage or blockages.Intelligent robots, armed with lights and a

video camera, make these inspections easier.Some robots are operated by remote

control, but the control cables can gettangled round bends. The latest high-techrobots, such as this German version, onlyneed a digital map of the sewers to get to

any point and examine the pipes.

Emergency water Fire hydrants are a crucial part of the emergency

water systems. The water that supplieshydrants comes from large tanks usually

located on hilltops. These tanks oftenconnect to hydrants by a system of pipes

laid out in a grid pattern. This allows water totravel from any tank to any hydrant via

several routes. Firefighters, such as thesein New York, attach a hose to a hydrant

and open the valve with a wrench.Water then runs down from the tank,

through the pipes, and blasts out of thehose at high pressure.



Water for livestockLivestock, such as these beef cattle, need plenty of water if they

are to thrive. They drink water daily, and the grass and other plantsthey eat need water to grow. Extra cattle feed – such as pellets made

from barley – need water to produce them too. If the cattle are broughtinto sheds, these must be washed down regularly. All in all, a single

animal requires tens of litres of water a day to keep it healthy.

Worldwide, more than 60 per cent of supplied water is used foragriculture – to feed crops and to provide drinking water andfood plants for domestic animals. Irrigation, which controls thesupply of water to farmland, can be an efficient way for farmersto use water. However, the demand for water from towns andcities, as well as for the land, almost exceeds supply, and peopleneed to find ways to get “more crop from each drop”.

Greening the desert It is possible to grow crops in deserts, as long as there is some rainfall or dewthat can be harvested. Alternatively, water can be brought in from elsewhere.By growing plants close together, as here in Chile, it creates a region of moistair around the plants, which cuts down evaporation.

MicroirrigationWhen water is sprayed onto the land, a quarter of it may never reach the plantroots because it evaporates from the soil surface. Microirrigation isa system of piping water directly to the plants, with only as much wateras needed trickling out. Here, onion plants are being irrigated in this way.



Sewage reed beds

Waste water from farms is usually rich in nutrients but may alsocontain waste matter and organisms from domestic animals.This water can be harmful to people and wildlife if emptied

into the sea or a river. Beds planted with reeds, such asthis one in Scotland, can naturally clean waste water.

Bacteria (microbes) in the soil beneath the reedsdigest the sewage and help to purify the water.

Rice paddy terraceFarmers in southeast Asia make the best use of the land by cutting terracesinto the sides of the hills. Rain fills these thin strips of land, which makes themideal for growing rice. More than half the world’s population relies on rice as amajor part of their diet.

GreenhouseCultivating plants in a greenhouse is one way of conserving water while controllingthe conditions under which they grow. Water that evaporates from the soil ortranspires from the plants stays longer within a greenhouse. High-value crops,such as tomatoes, are often grown this way.

need

Water for food productionIt is surprising how much water is used to produce food – and

how widely that requirement varies. For plants, it takes almost twiceas much water to grow rice than it does the equivalent weight oforanges. Animal produce, such as chicken and beef, requireseven greater amounts. This is because domestic animals eat plantsthat have already been grown using water, and the animalsthen need their own supply of water as well. Thischart compares how much water is needed toproduce 1 kg (2.2 lb) of some popular foods.

15,000 litres(26,396 pt)

beef

needs

chicken

needs

needs needs

1,000 litres(1,760 pt)

6,000 litres(10,558 pt)

1,200 litres(2,112 pt)

2,000 litres(3,520 pt)

oranges

ricewheat



From food to fabric, crayons to cars,and petrol to paper, virtually everythingwe use or consume needs water to makeit. Water can be involved in chemicalreactions, such as producing hydrogen ormaking plastics. In many cases, water acts as asolvent, dissolving and diluting chemicals. For the

metal and electrics industries, water transfers heat,cools objects down, and cleans products. In somedeveloped countries, more than half of the entirewater supply is used by industries.

Cooling towersIn power stations, the process of burning fossil

fuels releases heat. This turns large amounts ofliquid water into steam, which drives turbines togenerate electricity. Inside a power station’scooling towers, evaporation cools waste waterso that it can be returned to the river from whereit originally came.

Petrochemical worksDeep below the seabed and some parts of

the ground lie petroleum oil and naturalgas. These fossil fuels are drilled out

for the petrochemical industry.



for the petrochemical industry.They are used in the productionof organic (carbon-containing)chemicals, involved in makingplastics, paints, detergents,

and other household items.Water plays an essential

part – 10 litres (18 pt)is needed to produce just

1 litre (1.8 pt) of petrol.

Sand blasting Water blasted at high

pressure has tremendous

cutting power. If particles ofhard sand or gemstones (called“abrasives”) are mixed with this

water, the spray can cut likea knife or chisel. Here, a

water and abrasive jet isbeing blasted out to cut

through sandstone rock.

Silk dyeing These colourful Indian saris

are made of silk. The fibres arefirst washed, untangled, and

spun using large amounts ofwater, then they are woven

into cloth. More wateris involved in dyeing,

printing, and washing thesilk before it is cut and

sewn into clothing.

Waste water All industries produce waste water,which contains chemicals that

can be harmful to wildlifeand people. This wastewater is usually treated beforeit can be released safely intothe environment. Here,

waste water from

a chemical plant is beingemptied onto a beach.

Paper making As much as 1 litre (1.8 pt)of water is used to make

each A4 sheet of paper youwrite upon. Paper making

begins with wood chips beingbroken down into fibres byvarious stages of washing,

heating, and treating. Floatingwood fibres are then caught on

a perforated flat surface and thewater is squeezed out to leave a

large sheet of paper.

Our rivers and seas are becoming more polluted –by people and industries releasing high levels ofharmful substances into the environment. Almosteverything we spill throw away burn or bury



everything we spill, throw away, burn, or burywill eventually find its way to the sea. Evenfumes that float as air particles finally settle on

water, while falling rain can carry pollutionout of the air or off the land.

Too many nutrientsThis river in Thailand is rich in nutrients, such as nitrates and phosphates, thathave been washed into the water from fields. People have also put untreatedsewage into the river. The nutrient-rich water has caused microscopic plants calledphytoplankton to bloom, staining the river green. But few other organisms cansurvive in these conditions, and microbes from the sewage are a health hazard.

Waste from minesThis copper mine emptied its polluted waste water into a river. The waste wateris laden with particles of rock, called sediment, along with traces of copperand other heavy metals. The particles smother any water-living plants and smallanimals, and the heavy metals can be poisonous to plants and wildlife. In mostdeveloped countries, this type of pollution is now illegal.

Tainted watersIn November 2002 the oil tanker “Prestige” broke

49



Threatened whalesHarmful chemicals in the St Lawrence River, Canada, are threatening the localpopulation of beluga (white) whales. Heavy metals and pesticides wash orempty into the river and are taken in by the fish and shellfish on which the belugasfeed. When these substances get into the whales’ tissues, they can cause cancersand other life-threatening conditions.

Clean-up operationIt is better to prevent pollution in the first place, rather than clean up after ithas happened. Here, an oil spill is being contained within floating boomsbefore it is sucked up onto a vessel. However, in most cases of pollutionthere is no way of retrieving harmful substances once they have made theirway into the environment.

In November 2002, the oil tanker Prestige brokeup and sank off the coast of Spain. More than halfthe ship’s cargo of fuel oil spilled into the AtlanticOcean. Fuel oil contains poisonous substances that

can be taken in by plankton and fish, then passedon to any creatures that eat them. After this spill, alllocal fishing had to be halted.

50



Water ratioElectric charges fasten water molecules together like

people linking arms. When molecules join across thesurface of water, they form a “skin”, called surfacetension. It can support the weight of insects like thispond skater.

Too much or too little water can have devastating consequences.When rivers burst their banks, or a tsunami hits, the resulting floodscan sweep away buildings, crops, cattle, and people. At the otherextreme, a temporary shortage of water can kill crops and cattle.During droughts in poorer countries, people die from lack offood and clean water. The extent to which people areaffected by flood or drought depends on local climate

and the resources available to combat the effects.

Hurricane hitsIn some places, floods are

such rare events that emergencyservices are not prepared. On 29th August, 2005,

Hurricane Katrina slammed into the US city of New Orleans.It created a storm surge nearly 9 m (30 ft) high. The water

overwhelmed the levees (large embankments) built to protect the cityfrom floods. Helicopters dropped sandbags in an effort to seal the break.

Monsoon floodsIn many Asian countries, from India to

Japan, floods happen every year. In summer,monsoon winds bring torrential rain that

drenches towns and cities. The areasof highest flood risk lie around

the mouths of mighty rivers suchas the Ganges and Yangtze.

51

3 millionFlood & drought facts

people a year lose homes in floods



500–2,000 mm

(20–80 in)

Less than500 mm (20 in)

Desert advancesThe spread of desert into surrounding farmlandis known as desertification, and it is a growingproblem. Although this is partly due to global climate

change, a lack of moisture-rich vegetation is alsoto blame. When cattle overgraze or farmers burn

vegetation, desertification speeds up. Here in China,workers are planting suitable crops to help bind the soil.

Precipitation around the worldAverage precipitation varies greatly, asthis map shows. Near the coast, wheremoist winds blow, rainfall is often high.Conditions are drier inland – such asin North America and Asia. Near theEquator, rising warm, moist air createsheavy rainfall. Where dry air descends,

as in parts of South America, southernAfrica, and Australia, there are deserts.These are places with less than 250 mm(10 in) of rain a year.

1 in 12

30%

Annual precipitation

More than2,000 mm (80 in)

NORTH AMERICA ASIA

AFRICA

SOUTH AMERICAAUSTRALASIA

EUROPE

AtlanticOcean

Pacific Ocean

On dry landA water shortage occurs regularly in many places,including southeast Australia, southern California inthe USA, and Sudan in Africa. A slight shift in aircirculation is all it takes for the moisture-laden windsthat arrive one year not to return the next. While richcountries make up for this by bringing in water fromother parts of the country, in poorer countriesa water shortage can mean huge loss of life.

IndianOcean

13 m (43 ft)people a year lose homes in floods

of rain a year in Lloro, Columbia,

makes it the wettest place on Earth

people is chronically short of water

of the world’s land may facedrought by the end of this century



MeltdownOne effect of global warming is melting icearound the North and South Poles. Already,the expanse of sea ice in the Arctic appears tobe shrinking. Sea ice that melts will not affect

sea level because it is already in the water.However, ice on land that melts and runs intothe sea will raise sea level. This Alaskan glacieris shedding ice into the sea.

In the last century, the temperature of Earth’s surface has risen by 0.6°C(1.1°F). Meanwhile, carbon dioxide levels in the atmosphere have risenby almost 25 per cent. Many scientists link these changes. Carbon dioxide isa greenhouse gas, which means it absorbs infrared radiation – heat radiatingfrom Earth. Extra carbon dioxide comes from people burning coal, oil, and gasin their homes, offices, vehicles, and for industry. With more of this gas in the

air, more heat gets trapped in the atmosphere, and theplanet’s surface warms up. This may be the cause of

the current global warming, which is changingthe distribution of water on the planet.

Island floodsSurrounded by the Indian Ocean, the smallcity of Male in the Maldives is little more than1 m (3 ft) above sea level. Climate expertsestimate that global warming might raise the

level of the world’s oceans by about 0.5 m

(20 in) in the next 100 years. Most of this risewill come from seawater expanding slightly as

it gets hotter. Low-lying tropical islands, suchas the Maldives, would be at great risk of flooding.



Weather alert With global warming,weather across much ofthe world will become moreunpredictable. Extreme weather,including hurricanes and snowstorms, such

as this one in New York, USA, are expected tooccur more often.

Crop failureThis maize crop in Texas, USA, is wiltingfrom the heat of the Sun. Global warmingwill cause droughts (lack of water) in placeswhere droughts do not currently occur.

Farmers in such regions may have togrow different crops or cultivate specialdrought-resistant strains of the cropsthey grow at present.

Pastures newIf global warming continues, parts of the world will

become warmer and wetter, while otherswill turn cooler and drier. These changes will

cause the distribution of animals to shift,

as they relocate to the climates that suitthem best. For example, swarms

of locusts that currently eatcrops in northwest Africa may

move north into southernEurope and western Asia.

Traffic pollutionThese New York taxis are releasingcarbon dioxide into the atmospherethrough their exhausts. In the USA, about33 per cent of carbon dioxide emissions comefrom cars burning petrol or diesel. Another 40 per centcomes from burning fossil fuels to generate electricity. One wayto combat global warming would be to find alternatives to burningfossil fuels. This would help counter the rising levels of carbondioxide in the atmosphere.



To face the future with some hopeabout water supplies, scientistsand engineers are developingtechnologies that will makethe best use of this essentialresource. However, thereare grave imbalances –many developed countries

are wasteful, while somedeveloping countries do nothave enough water. Peopleacross the world will have torecycle and conserve water moreefficiently than they do at present, if everyone is to geta fair share and the global environment is not put in peril.

Eden Project This environmental complex in Cornwall, England, centres on a seriesof bubble-like greenhouses that grow plants from several climaticregions. Studying these plant communitieshelps scientists understand how wateris used and recycled in nature.This, in turn, provides ideas forways people can work inharmony with nature to

maximize recyclingand minimizewastage.

Increased demandsAs the world’s population continues to rise, more

people are chasing fewer natural resources. Inmany areas, fresh water for drinking, irrigatingcrops, and safe sanitation is becomingincreasingly scarce.

Eyes in the skySatellites can relay crucialinformation to expertson the ground. In 2007,European scientists launch

the first satellite that willmeasure the salinity (saltiness)

of the sea surface. This ENVISAT

satellite image of the Aral Seashows how this giant lake has shrunk

to a patchwork of smaller lakes.

Ocean technologyEngineers are learning how to tap previously

unused sources of water. Here, in theMediterranean Sea, fresh water is beingpiped to the surface from a spring that is36 m (118 ft) down on the seabed.

55



A world with safe water In March 2005, the United Nationslaunched its Decade of Water for

Life (2005–2015). At the momentabout one person in every six

worldwide has no access to safedrinking water. One of the aims ofthe campaign is to greatly improve

this figure by helping communities toset up facilities for digging wells

and pumping up waterfrom aquifers.

( )The water flows naturally undergoundfrom the mountainous Alps onmainland Europe. Passing ships

can stop and collect the water.

Fish farming Today, more than 30 per centof the fish people eat is farmed

in ponds or cages. Thispercentage will rise as peoplecontinue to overfish the open sea.With coastal waters becominglyincreasingly overcrowded – largely dueto recreation – technologies are beingdeveloped to locate fish farms furtherout to sea.

56



The WorldHealth Organizationestimates that three

people a minute die dueto unsafe water and

poor sanitation. Mostare children.

The amount of waterthat arrives on Earth each

year, carried by comets andmeteorites, is about the

same amount that escapesback into space.

A tap thatdrips once every

10 seconds wastesmore than 1,000 litres

(264 gal) of watera year.

The Three GorgesDam in China should protect

about 300 million people fromfloods. However, two million

people have had to movebecause of the lake that

feeds the dam.

Today, more than

90 per cent of theworld’s glaciers areretreating due toglobal warming.

Canada hasthe longest marine

coastline inthe world.

Some Greekislands get their

drinking water fromships that tow giant bagsfull of 2,000,000 litres

(528,346 gal)of water.

Most homes in theworld do not have a tapfor drinking water. The

majority of people have toget their water from acommunity supply.

In someindustrialized

countries, about30 per cent of the

water used at homeis flushed down

the toilet.

In Namibia, Nepal,and Norway, morethan 90 per cent of

electricity is generatedby hydroelectric dams.

When lightningstrikes a tree, thewater inside mayboil, blowing the

tree apart.

Fruit andvegetables aremainly water –tomatoes are

95 per cent andapples are

85 per cent.

In the USA,

farm animals produce130 times moresolid and liquid waste

than the humanpopulation.

The Ogallala Aquifer

in the USA contains“fossil water” thatis tens of thousands

of years old.

One of theplanet Jupiter’s

moons, Europa, may

have giant oceansbeneath itssurface.

In the last200 years, about halfthe world’s wetlands

have been lost, mainlyto draining foragricultural use.

More thanhalf the populationof the USA relieson ground waterfor their water

supplies.

57

When electricityis passed through

water in a controlledprocess, it splits water

The amount ofwater on Earth has

stayed roughly constantfor millions, perhaps

billions, of years.

The waterfrom the equivalent of350,000,000 Olympic

swimming poolsevaporates from



In the UK, an averagehousehold spends lessthan 0.02 per cent of

income on water. In Ugandaa household spends morethan 3 per cent, while inTanzania, it is more than

5 per cent.

The humankidneys filter about170 litres (300 pt)of blood for everylitre of urine they

produce.

The roof of thebuilding at Frankfurt

Airport captures more

than 15,000,000 litres(3,962,593 gal) of rain ayear. This water supplies

gardens, toilets, andother facilities.

Australia isthe world’s driest

inhabited continentwith rainfall averagingonly 455 mm (17.7 in)

per year.

The wettest24 hours was on

16th March 1970,when 1.9 m (74 in)

of rain fell on ReunionIsland in the Indian

Ocean.

p pinto its basic elements –hydrogen and oxygen.

These gases can becollected.

In parts of China,India, and the USA, groundwater is being used more

quickly than it is beingreplaced. As a result,water tables are falling

dramatically.

In some rivers,such as China’s

Yellow River, so muchwater is used by people

that the river runs drybefore reachingthe sea.

Scientists calculatethat if Earth had been8 per cent nearer the

Sun, life would not haveevolved. It would have

been too warm for

liquid water.

The Dead Sea is likea lake with no link toopen sea. It is 415 m(1,362 ft) below sea

level, the lowest bodyof water on Earth.

The surface ofMars is markedwith trenches, whichmay once have been

rivers. The wateron Mars today

is frozen.

In developingcountries, more than

two-thirds of industrialwaste water is dumpedinto the environment

without beingtreated.

Since 1957, theAral Sea in Kazakhstanhas shrunk in volume

by two-thirds as itswater has been used

to irrigate land.

On 3rd September1970, a hailstone

weighing 0.77 kg(1lb 11 oz) fell inKansas, USA.

About 80 per centof the sickness and

disease in developingcountries is

water-related.

y pEarth’s surface

each day.

Each time youbrush your teethwith the tap running

it uses up to 7.5 litres(2 gal) of water.

An oak treetranspires about

1,000 litres (264 gal)of water a day – theequivalent of three

baths full ofwater.

If all the water inthe Great Lakes was

spread across the USA,the ground would be

covered with 3 m(10 ft) of water.





60 Glacier Large mass of snow and ice on

land that builds up by repeatedsnowfalls. It flows slowly downhillunder its own weight.

Global warming



Condensation

Process of a gas turning intoa liquid, such as water vapourcondensing into water droplets.

ConvectionVertical circulation of a liquid orgas due to warm regions risingand cool regions sinking.

Coral reef

Limestone rock produced inwarm, shallow sea water by smallanimals called hard coral polyps.

Coriolis effect Effect of Earth’s rotation to turna wind or ocean current. Thiseffect turns ocean currentsclockwise in the NorthernHemisphere and anticlockwisein the Southern Hemisphere.

Dark zone Lower region in an ocean,deeper than 1,000 m (3,300 ft),where no sunlight reaches.

Delta Plain formed by the mouth ofa river depositing sediment.

Displacement Mass of water pushed asideby an object floating, sinking,or settling in the water.

DissolveTo make a substance disperseand disappear in a liquid.

Drought An extended period of little or

no rainfall.

Element Single substance that cannot

Acid rain

Rain made more acidic by airpollution, especially from burningfossil fuels in homes, powerstations, and motor vehicles.

Air massBody of air with fairly uniformtemperature and humiditystretched over many miles withinthe lowest part of the atmosphere.

Aquifer Region of rock or soil beneaththe land surface that is saturatedwith water and through whichwater can move to supply wells.

Artesian wellWell that receives water underpressure from an aquifer. Waterrises to a ground level without

being pumped.

AtmosphereLayer of gases surrounding Earth.

AtomSmallest part of a chemicalelement.

Buoyancy

Upward pressure on a floatingobject produced by the waterit pushes aside.

CellTiny unit that makes up an animalor plant body. A cell contains acentre, called the nucleus, andhas an outer boundary, the cellmembrane. Most animals andplants contain millions of cells.

ClimateGeneral pattern of weather in a

specific region over many years.

Global warming Gradual increase in the averagetemperature across the world.

Gravitational attractionForce of attraction between largemasses. Heavier masses havegreater gravitational attraction.

Greenhouse effect Trapping of infrared radiation fromEarth’s surface by greenhousegases in the atmosphere,

producing a warming effect.Greenhouse gas Gas that absorbs infraredradiation, so trapping heat inthe atmosphere. Carbon dioxide,methane, and water vapour aregreenhouse gases.

Ground water Water lying in soil or rock that

may seep through it. Groundwater supplies wells and springs.

GyreLarge circular system of currentsin an ocean.

Hard water Fresh water that containshigh levels of dissolved calcium

and magnesium.

Humidity Amount of water vapour in theair. The greater the humidity, thehigher the water vapour content.

Hurricane Violent, spiralling tropical stormwith wind speeds in excess of119 km/h (74 mph).

Hydrogen bondForce of attraction between

water molecules.

be split into other substances

by normal chemical means.

Energy Ability to cause an action. Energyis not destroyed, but it changesfrom one form to another.

Erosion Processes by which rock or soilare loosened and transported byglaciers, rivers, wind, and waves.

EstuaryWhere a river meets the sea andfresh water mixes with sea water.

Evaporation Process of liquid turning intoa gas (vapour).

Flood

Water flowing onto ground thatis normally dry.

Floodplain Area of flat land over which thelower river floods naturally.

Fossil fuelFuel such as coal, oil, or naturalgas that forms from the remains

of long-dead organisms.

Fresh water Water low in dissolved salts. It isdefined as water containing lessthan 0.1 per cent dissolved salts.

Front Forward moving edge of an airmass, such as a cold or hot front.

Geyser Vent in the ground from which

erupts volcanically heated waterand steam.

Hydrothermal vent Seabed opening that releases

volcanically heated water.

Ice age Cold period in Earth’s historywhen glaciers and ice sheets

Ocean current Major flow of seawater. Surface

currents are normally driven bywinds or temperature differences,

with warm sea water rising andcool sea water sinking.

Sea Water in an ocean. It is also the

name for part of an ocean, suchas the Caribbean Sea.

Sea ice Ice forming as sea water freezes.

Synovial fluidFluid that lubricates human

joints, reducing wear and tearon bones.

Tide Rise and fall of sea water produced

61



when glaciers and ice sheetscovered much of the land.The most recent ice age ended

about 15,000 years ago.

Ice sheet Large, thick layer of ice coveringa landmass. Ice sheets covermost of Greenland and Antarctica.

IrrigationSystem for supplying farmlandwith water by channels or pipes.

Levee Raised bank along the lowerreaches of a river, built fromsediment deposited during floods.

Meteorite A rock that falls from space andstrikes the Earth.

Micro-organisms (microbes)Microscopic organisms.

MineralSubstance that is found in rockand may dissolve in water.

Molecule Smallest amount of a substancewith the properties of thatsubstance. It normally consists

of two or more atoms heldtogether by chemical bonds,as in water (H

2O).

Monsoon Seasonal winds that blow acrosssouthern and eastern Asia.Summer monsoon winds bringheavy rains from moist air abovethe Indian and Pacific Oceans.

NutrientsThese are substances such as

nitrate and phosphate that plantsneed supplied in order to grow.

Organism A living thing.

Photosynthesis Process by which plants, andplant-like micro-organisms,make food by trapping sunlight.

Phytoplankton Plant-like micro-organisms thatlive in the sea and in fresh water.

Plankton

Organisms that float in the sea,lakes, or slow rivers and getpushed along by currents.

PollutionPeople releasing substances, orfactors such as heat or sound,into the environment at levelsthat could be harmful to wildlife.

Precipitation Water falling or settling from theair onto land or sea. Rain, snow,sleet, hail, frost, and dew aretypes of precipitation.

Salt Substance commonly formed bythe reaction between an acidand an alkali or an acid and a

metal. The most common saltis sodium chloride, which goeson food and is the main typeof salt found in sea water.

Saltwater Water that contains high levels ofdissolved salts. Saltwater is foundin the sea and some inland lakes.

Satellite Object that orbits a planet.

Artificial remote-sensing satellitesorbit Earth monitoring the weather

and land and sea conditions.

Ice forming as sea water freezes.

Sea wave

Vertical disturbance that travelsalong the sea surface. Most seawaves are wind driven. Thelargest waves (tsunamis) comefrom earthquakes, volcanoes,landslides, or meteorites.

Sediment Loose material eroded from theland and deposited elsewhere.

Sewer System of underground pipesthat carry waste water away fromhouses, businesses, factories,and to water treatment works.

Soft water Fresh water that contains lowlevels of dissolved calciumand magnesium.

Stalactite Hanging, icicle-like structuremade of calcium carbonate.

Stalagmite Rising, candle-like structuremade of calcium carbonate.

Stomata (stomatal pores)

Openings on the stem and leavesof plants. Water vapour escapesthrough stomata and other gasesenter and leave through them.

Sunlit zone Upper region in an ocean, definedas shallower than 200 m (660 ft).Here, enough sunlight reachesthe plants and plant-like micro-organisms for photosynthesis.

Surface tensionAttraction between water

molecules at water’s surface.

Rise and fall of sea water producedby the gravitational attraction ofthe Moon and the Sun.

Transpiration Loss of water from plants byevaporation.

Tsunami (harbour wave)Large, fast-moving wave, or seriesof waves, that moves acrossthe ocean. It is created by thedisturbance from an earthquake,volcanic eruption, or large massstriking the water surface.

Twilight zone Region in an ocean, at a depthbetween 200 m (660 ft) and1,000 m (3,300 ft). Sunlightreaches this zone but not enoughfor plants or plant-like micro-organisms to photosynthesize.

Waste water Water that has been used inhomes, businesses, or industry.

Water cycleConstant cycling of waterbetween sea, air, and land.It involves evaporation,condensation, precipitation,and percolation.

Water table Level below which soil or rockis saturated with ground water.

Weathering Breakdown of rocks byphysical, chemical, andbiological processes ator near Earth’s surface.

Zooplankton Drifting animals and animal-like

micro-organisms that live in thesea and fresh water.

62

Great Lakes 16, 57greenhouse gas 52, 60greenhouses 45ground water 7, 30, 40, 41,

56, 57, 60



Aacid rainwater 25, 32, 60acids 9agriculture 44air circulation 26air mass 27, 60algal blooms 14alkalis 9altostratus 28animal plankton 14animals distribution of 53 streamlined shape 14, 15aqueducts 58aquifers 30, 34, 60Aral Sea 57artesian wells 40, 60atmosphere 8, 11, 26, 52, 60atoms 4, 60axolotl 15

B bacteria, see microbesBay of Fundy 22, 23blood 37, 57blue colour of seawater 6body water 36–37boiling point 5brackish water 8, 32

breathing underwater 15brushing teeth 57buoyancy 8, 9, 15, 60burning 5, 52

C calcium carbonate 41carbon dioxide 12, 14, 52caves 34, 41Celsius temperature scale 5

chlorine 58cirrus 29climate 26, 60

clouds 7, 11, 28–29 facts 29 formation 28coal, oil and gas, see fossil fuelscoastline, longest marine 56coccolithophorids 14cold fronts 27condensation 27,

35, 60contrail 29convection 26, 28, 60cooling towers 32, 46copper mine 48coral reefs 20, 60Coriolis effect 22, 60crops 32, 44, 45, 58 failure 53currents, ocean 22–23cumulonimbus 29cumulus 28

Ddams 32, 38, 39, 58, 59Dead Sea 9Decade of Water for Life 55delta 19, 33, 60desalination plant 32, 33, 59desertification 51deserts 34, 44, 51dew point 29

digestive juices 37dirty water 42, 48–49, 57diseases 42, 59dissolving in water 5, 60drinking water 42, 55, 56droughts 50–51, 53, 60

EEarth 6–7, 57 amount of water 31, 57

surface temperature 52 water evaporation 57Eden Project 54

electrical charge 5electricity generation 38, 39, 46emergency water system 43energy of water 38, 60erosion 18, 24, 60estuary 8, 32, 60Europa 56evaporation 31, 33, 35, 57, 60

Ffacts and figures 56–57Falkirk Wheel 39farming 44, 45, 53, 58fire hydrants 43fish 15, 20, 21fish farming 55floating on water 8, 9, 10floodplain 19, 60floods 50–51, 52, 60fog 29

food production 45forests 34fossil fuels 47, 52, 53, 60fossil water 56freezing 4, 5, 25freezing point 5, 10fresh water 8–9, 10, 16, 41,

44, 55, 60fronts, frontal systems 27, 60frost, and weathering 25

frozen water 10–11fruit and vegetables 56

Ggas 4, 58geysers 40, 60glaciers 7, 10, 25, 56, 59, 60 facts 25global warming 52–53, 60Grand Canyon 24

gravitational attraction 22, 60gravity 5grease ice 11

Gulf Stream 23

HH2O 4–5

hailstones 27, 57heavy metals 48, 49household spend on water 57humans kidneys 57Hurricane Katrina 27, 50hurricanes 27, 50, 60hydraulic ram 58hydroelectric power 38, 59hydrogen 4, 57, 58, 60hydrothermal vents 21, 61

I, J, Kice 4, 5, 10–11 and weathering 25ice caps 7ice cores 11

ice crystals 4, 11, 27, 28ice floes 11ice sheets/ice fields 10, 11, 61icebergs 10, 33industry 32, 46–47irrigation 32, 44, 61

LLake Baikal 16, 17

lakes 7, 8, 16–17 important 16, 17Law of the Sea 59leaves 12life in water 14–15, 20–21light, underwater 6, 21limestone 25, 34, 41liquid water 4livestock 44living organisms 6, 7locks 58

MMale, Maldives 52meanders 19melting 5, 52

l 18 39

Plimsoll line 8Poles (North and South)6, 10, 52, 59pollution 48, 53, 61 and weathering 25

l 49

sewage reed beds 45sewers 31, 42, 43, 58, 61 robots 43sharks 15silk dyeing 47k i 11

industrial 47, 48, 57water 4–5 amounts on Earth

6–7, 31, 57 capturing 57f 5

63



meltwater 18, 39microbes 16, 42, 45

microirrigation 44mineral water 59mist 29monsoons 50, 51, 61Moon, and tides 22mountains 18, 33

N nimbostratus 28nitrates 48nutrients 48, 61

Ooasis 34ocean floor 21oceans 6, 7, 8, 20–21, 55 deepest point 59 exploration 20, 21, 59 first 6, 57, 58

pressure/temperature 58 rise in levels 52 zones 20, 21oil spills 49, 59ox-bow lake 19oxygen 4, 14, 57, 58

P,Qpancake ice 11

paper making 47Panthalassa 58percolation 30pesticides 49petrochemical works 47pH scale 9photosynthesis 12, 13,

14, 61phytoplankton 14, 48, 61plant plankton 14plants 12–13, 16

and weathering 25 floating seeds 23plasma (blood) 37

clean-up 49ponds 16–17

pools tree (rainforest) 16 vernal 17population, and water needs 54power stations 32, 46precipitation 30, 61pure water 5, 9

Rradiolarians 14rain 6, 27, 28, 34 and weathering 25 wettest 24 hours 57raindrops 27, 35rainfall, average 51, 57rainforests 51 pools 16rapids 18recycling water 54reeds 17, 45

reservoirs 39rice growing 45rivers 7, 8, 18–19, 24, 32 longest 19 run dry 57rock, weathered 25roots, plant 13rural water 44–45

Ssafe drinking water 55salt 5, 8–9, 11, 61saltiness (salinity), measuring 54salty water 8–9, 61sand blasting 47sanitation 56, 57satellites 54, 61sea ice 11, 52, 61sea level 52seawater 6, 8–9, see also oceans

sediment 16, 17, 19, 24, 48, 61sewage 42, 48sewage plants 31, 42

skating 11skin 36

smokers, undersea 21snow 25, 28, 34snowflakes 11sodium chloride 8solid water 4stalactites 41, 61stalagmites 41, 61steam 5, 6, 35, 57steam engine 58still water 16–17stomata 12, 61streams 18sunlight 6surface tension 4, 61swamps 16sweat, sweating 36, 37synovial fluid 37, 61

Ttap water 42

taps dripping 56 running 57Three Gorges Dam 56, 59tidal barrages 39, 59tides 22–23, 39, 61timeline 58–59toilets 31, 56, 58traffic pollution 53transpiration 13, 35, 61

trees 12, 56, 57tsunami 59, 61

U, Vunder the ground, water 40–41underground reservoir 31urban water 42–43

Wwarm fronts 27waste from animals 56waste water 31, 42, 43, 45, 61

facts 5first life forms in 14

future demand for 54gas 4, 35in Space 5, 56liquid 4, 35on the move 31–34shortages 51, 54solid 4, 35water cycle 30,33, 35, 61 mini 31water drops/droplets 5, 28water molecule 4, 5, 13water power 38–39water purification 59water supply tunnel 59water table 40, 57, 61water treatment 32, 42water use in industry 32, 46–47 in towns/cities 31,

42–43water vapour 27, 28, 33

waterfalls 18waves 22, 23, 24weather 26–27 extreme 53weathering 24, 25, 61wells 34, 40wetlands 16, 32, 56whales 15, 49winds 22, 23, 27wood 12

World Health Organization 56

X,Y,Zzooplankton 14, 61





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