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skin diving, spearfishing, surfing, water polo, and water
skiing. The Olympic Games program includes swim-
ming, diving, and other water sports (see Olympic
Games). All water sports mentioned here have separate
articles in World Book. SamJ.Greller

WATER STRIDER. See Water Bug.



WATER SUPPLY. Our earth has life because it has
water. Wherever there is water, even in small amounts,
life is usually found. But where water supply is limited,
there is little life. Few places on earth have less life than
the desert sands and the polar icecaps.

People need only a small amount of water to live,
because they drink only a few quarts each day. This
amount would be more than enough if man used water
onlv for drinking purposes. But civilized man has many
uses for water besides drinking it. He uses it to bathe
himself, to cook his food, and to wash his dishes and
clothing. Water irrigates his crops and thereby increases
his food supply. Modern factories run on water. It takes
270 tons of water to make a ton of steel. 1,400 tons of
water to make a ton of rayon, and 4,700 tons of water
to make a ton of synthetic rubber. For cveiy gallon of
water used for cooking and drinking, 25 to 50 gallons
are used to wash and flush away dirt and human waste.
Without good water supplies, it would be impossible
for a modern city to meet all these human needs. Ameri-
can water systems produce enough water each day to
supply every person with about 1 50 gallons.

It is not surprising that cities have grown up near
large water supplies furnished by rivers and lakes. Na-
tions without adequate water supplies arc never pros-
perous. Early civilization flourished in Mesopotamia
near the Tigris and Euphrates rivers. These same civili-
zations disappeared when water reservoirs and canals
filled with silt and when the irrigation systems failed.

Sources of a Water Supply

Natural sources supply the cheapest water available.
In areas that have no other source of water, people get
water from wells. If the underground water is unsuit-
able, rain water from roofs can be collected and stored
in cisterns (storage tanks for water). Gro\\ing commu-
nities and indusuies soon use more water than wells can
provide. \Vhen this happens, they use the water sup-
plied by streams and lakes. Along seacoasts or on islands
where there is no supply of fresh water, people often
make fresh water from sea water.

Rain Wafer supplied most individual needs during
the early growth of the United .States. There were no
public water-supply systems, and wells had to be dug by
hand. The rain water drained from the roof into a cis-
tern that was usually built under the back porch or
kitchen. The water was then pumped from the cistern
into an old-fashioned sink. Today, only a few localities
depend on rain water for their water supplies.

Rain water is sojt. This means that it contains no
dissolved mineral salts from the ground. But it does
contain dust from the air and from the surfaces that it
touches. Dust particles can be removed by filtering rain
water through sand.

Underground Water exists even.-where beneath the
surface of the ground. It may be near the surface or
down ver)' deep. It may be salty or fresh, soft or hard.
The carbon dioxide in some tmderground water corrodes
metal pipes. Underground water seldom contains bac-
teria because it has been filtered through the soil.

Ground Water is rain water that has soaked into the
ground and slowly filtered downward. It eventually
comes to a zone where the soil and the rocks are satu-
rated with water. The top of this saturated zone is called
the water table. .See Ground Water.



W'







fta^.;



Chioap.t nridgo & Iron Co.

A 77-Foot-High Watersphere stores water for the village
of Colomo, Wis. It has a 40,000-gollon water capacity.

Wells that reach the water table yield large quantities
of water, provided the pores in the soil are large enough
to let the water pass through. In indusuial and irrigated
areas, the water is almost always taken from the ground
faster than it can filter down from the surface. This
depletes ground-water storage, and lowers the level of
the water table. The water level may fall so deep that
pumping out water becomes expensive. See Well.

Floodwaters are sometimes spread in large beisins to
increase the supply of ground water. The basins hold
the floodwater within a large area. They let the flood-
water filter slowly into the ground, instead of flowing
away rapidly (see Basin).

Surface Water supplies most of the water for large
cities and industries. These supplies consist of large lakes
and ri\ers, or smaller rivers on which dams have been
built to store floodwaters for future use (see Dam [What
Does a Dam Do?|). Chicago, Milwaukee, Cleveland,
and other cities get their water from the Great Lakes.
St. Louis and New Orleans use water from the Missis-
sippi River. New York Cit\-, Boston, and Baltimore
hav'e large storage reservoirs on upland streams.

Cities that depend on lake-water supplies build tun-
nels or pipelines and connect tlicm to an oflshore water
intake, where the water is relatively pure. Intakes are
usually towers equipped with screens to keep out debris.
They also have gates that contiol the depth at which
the water is withdrawn. The pumps and purification
plants are located on shore.

Cities remove river water in much the same v\'ay as
they remove lake water. They construct the intake up-
stream from the city to avoid taking in impurities from
water the cir>^ has already used. But the same river water
mav be used by several cities before it finally passes into
the ocean. For this reason, river water is often less
sanitan' than lake water.



107



HOW CITY WATER IS PURIFIED





LIME



ALUM

ACTIVATED CARBON

CHLORINE



City wafer is often purified by the Filtration method. First, if is
pumped to the chemical building where lime, activated carbon, alum,
and chlorine are added. From there, it passes to the coagvlation
basin where the chemicals are thoroughly mixed with the water.
The chemical reaction causes most impurities to coagulate, the
solid particles settling to the bottom as the water passes through
the sedimentation basin. To do away with bad tastes or odors which
remain, activated carbon is added before the water passes through
a bed of floe (gelatin mat), sand, and gravel in the filter basin. As
the water leaves the filtered water reservoir, chlorine and aluminum
sulfate are added to complete the purifying process before it is
pumped into the distributing main for daily use in homes and factories.




TUNNEL TO OTHER PUMPING STATIONS



Sea Water. Most of the water on earth is the salty
water of the oceans. The supph- of usable water would
be almost limitless if the salt could be removed easily
from sea water. On seacoasts or islands that have no
fresh water, it is sometimes cheaper to remove the salt
from the sea water than to bring in fresh water by ship.
But it is not cheap to remo\-e salt from sea water. The
process is complicated and requires much expensi\c
equipment (see Water [Converting Sea Water]).

Stored Water. Streams sometimes have to be regu-
lated in order to have a sufficient supply of water when
and where it is needed. Man>- communities store flood-
water behind dams and release it during the summer to
keep the streams from getting too low. The regulation
of stieams may not supply enough water to meet the
needs of cities and factories. In such cases, pipelines and
tunnels must be built to bring additional water from
other rivers (see Aqueduct).

Cities often build reserx'oirs in tlie hills and moun-
tains some distance from the city, where land is cheaper
and the water purer. Reservoir water resembles lake
water and is much purer than river water. Because of
the high elevation, water can often be brought to the
cit\' without pumping it. Pipelines, tunnels, and canals
cariT the water from the reservoir to the city. The dams
that form the reservoir usually have built-in intakes.
See Reservoir.

How Water Is Purified

As commonly used, the term pure water means that
the water is satisfactor>- for the use that it serves. Thus,
pure water for industry may not be pure water for
drinking. Drinking water must be clear, cool, and free
of any special taste or odor. It should contain some, but
not much, mineral salt. It should also be free of all
harmful bacteria and chemicals. But industrial water
may also have to meet more rigid specifications. For
example, water used in high-pressure steam boilers must
be completely free of dissolved oxygen, and it should
contain only a small amount of dissolved salts. The
parts in some pieces of electronic equipment must be
washed with water that is almost entirely free of dis-
solved substances. This water must be distilled several
times before it is pure enough to be used (see Distilla-
tion).

Most cities use three basic processes to purify water:
(1) coagulation and sedimentation, (2) filtration, and
(3) disinfection.

Coagulation and Sedimentation. A coagulant is a
chemical that forms a small, fluffy mass called floe in
natural water. Floe particles are about the size of snow-
flakes, and they help remove the suspended sediment
from water. They gather the suspended matter in water
and carry it to the bottom of large sedimentation tanks.
-Aluminum sulfate, also called fl/ter alum, is the most
common coagulant.

\ feeding machine continually measures out the
amount of alum needed. A stream of water carries the
alum to the point at which raw (natural) water enters
the purification plant. After about 30 minutes, the
coagulant has been thoroughly mi.xed into the incoming
water and the floe has formed. The coagulated water
then passes slowly through sedimentation plants where
the floe settles to the bottom along with the suspended
particles. Large scraping machines periodically remove



WATER SUPPLY

the mud or sludge that forms on the bottom of the sedi-
mentation tank. In some places, the sedimentation tank
is emptied about twice a year.

The process of coagulation and sedimentation re-
moves most of the bacteria and suspended matter from
water. But to produce a completely clear water and to
remo\-e all bacteria, the water must pass from the sedi-
mentation tanks to filters.

Filtration. \Vater filters consist of fine sand placed in
concrete or steel tanks. The sand forms a bed about 30
inches thick. The water filters down through the sand
to an underdrainage system that collects the water and
carries it to a clear water-storage basin. Eveiy minute
2 or 3 gallons pass through each square foot of the bed.

The first few inches of die sand bed trap the floe and
bacteria that remain in the water after coagulation and
sedimentation. The filter must be \vashed every day or
so because the floe clogs the sand bed. Washing is done
by forcing clean water up through the sand. \Vater
gutters above the sand bed collect the dirty water and
carry it off to a drain.

Disinfection is designed to keep water from carrying
infectious diseases. Disinfection can be accomplished
in a number of ways. Heating is the most reliable method,
but it is not practical for large quantities of drinking
water. Most water departments use chlorine because it is
cheap and acts rapidly (see Chlorine). Chemists find
it easy to detect and measure the amoimt of chlorine in
any given water supply. A very small amount of chlorine
quickly disinfects large quantities of water. One pound
of chlorine can disinfect 200.000 gallons of water. This
is more water than one person could drink in a thousand
years. Chlorine may be added to the water either before
coagulation and sedimentation or after the water has
been filtered.

Water may also be disinfected by processes using silver,
iodine, ozone, and ultraviolet light. But these processes
are not as cheap as chlorination. They also tend to be
less safe and must be carefully controlled.

Softening water can be done in a number of ways,
but the purpose of every method is to make soap easier
to use, to protect metal that comes in contact with the
water, and to make water generally more suitable for
home and industrial use. City water plants usually
soften water with lime or lime and soda. Water can also
be softened by a process of ion exchange (see Ioniza-
tion). A filter bed of zeolite, a claylike material, gives
up its sodium in exchange for the calcium in water (see
Zeolite). This softens the water that passes through
the zeolite bed.

Other Methods of Purification are used to remove
undesirable tastes, odors, and minerals from water, or to
give the water a special quality. After the water has
passed through the filters, lime is sometimes added to
keep the water from rusting pipes and the various me-
tallic parts of household plumbing systems. Odors can
be removed from water b\' aeration (forcing the water
into air in a fine spray). Many dues fluoridate drinking
water to help reduce tooth decay (see Fluorid.^tion).

Distributing Water

After the water has been purified, it must be dis-
tributed to homes, businesses, and industries. Water

io8a



A WORLD BOOK SCIENCE PROJECT MAKING PURE WATER

The purpose of this project is to learn how water from lakes and other sources
is treated to make it pure enough to drink. You can get the materials you need
to build a model purification plant from a hardware store and lumber yard.



PURIFICATION
PLANT

^CHEMICAL BUILDING




Most large cities use purification plants similar to the model,
above, to make water from lakes and other sources pure enough
to drink. The water first flows into cribs, which strain out large
particles of sand and other impurities. Pipes carry the water to
a mixing basin where it is thoroughly mixed with chemicals. The



chemicals cause fine impurities to clump together and settle to
the bottom of the sed/mentof/on basin. Finally, the water flows
slowly through filters mode mostly of thick layers of sand and
gravel, and collects in a reservoir. To complete the purification,
chlorine is added as the water moves from the reservoir to homes.



MATERIALS




Clear Plastic Tubing and Adhesive Tape



Tin Plate, Plastic,
Cork, Screw, and Nuts



Small Electric Water Pump



Lumber needed to make the display board, shelves, and stand is shown, below. You will also
need several different colors of paints to represent the chemicals added to the water.



1 in. X 6 in. lumber
(stielves)




24 in. X 36 in, plywood (display board) l\^



2^




4 bolts and nuts



Paint



1 in. X 2 in. tomber
(stand)




Illustrated by Kaymond Feilman for WORLD BOOK



ASSEMBLY



The Lake and Crib. Drill a hole near one corner of the rectangu-
lar pan as shown, be/ow. Push the funnel spout through the hole
and solder it in place. Solder the strainer basket to the top of
(he funnel. Put mounds of sand at the other end of the pan.



Tea strainer basket
Funnel



The Mixer. Cut and fold a tin plate as shown, be/ow. Drill a
hole above the fold. Put plastic fins in slits in a cork. Use a
screw as an axle. Push it through holes tn the cork and tin plate.
A nut on each side of the tin piate holds the axle in place.



Fine sand




The Filter is a plastic container with layers of ingredients
that filter impurities out of the water. Make a hole in the
bottom of the container and insert a plastic tubing drain.
Then put in layers of cotton, pebbles, coarse sand, fine
sand, and charcoal paste.



The Filtered Water Reservoir

in a real plant holds water ready
to be piped out to users. But in
the model, it sends water back to
the starting basin for use again.



The Display Board and Stand

are assembled as shown, obove.
Draw a plan on the board showing
where each piece goes. Point the
chemical building and consumer sec-
tion. Install braces for the shelves.
Put the containers in place and string
the plastic tubing from one to an-
other. Use adhesive tape to hold
the tubing in place on the board.



109




The Reservoir and Tanks

at West Seattle, Wash., can
store 8,500,000 gallons of
water. The water is delivered
to the city through pipelines
and tunnels.



II Water Works



distribution is the most expensive part of a water-supply
system, because it requires a vast network of pipes.

Distribution systems consist of four parts: (1) pumping
stations, (2) street mains, (3) reservoirs or tanks, and
(4) the plumbing and pipes in buildings.

Pumping stations lift the water to various heights and
maintain enough pressure to force the water through
the system to the fixtures or hydrants where it is used.
Water mains run beneath the streets and connect at
each intersection. They form a network of pipes that
carries the water to every consumer and every fire
hydrant.

At various times a city will use an excess of water,
because of a large fire or some other drain on the water
supply. In such cases, the pumping stations cannot
pump enough water. For this reason, a city must have
storage tanks to supply the additional amount of water.
The tanks help keep a uniform water pressure through-
out the city. During the day, the water level in the tanks
falls, but the tanks are refilled at night when the city
uses less water.

A pipe called the service connection connects the street
main to the piping system in homes and buildings. The
water company installs a water meter on the service
connection, usually near the sidewalk or curb (see
Water Meter). The water company owns all parts of
the water-suppl)- system up to and including the water
meter. The property owner must install all other pipes.

Conserving the Water Supply

Water is no longer free for the taking. The day is
almost gone when cities and industries can get water
from a nearby stream at the mere cost of pumping it
out. Water now has to be stored, transported, purified,
and distributed like any other product. Marketing of
this kind takes money.

Many communities claim that they have a water
shortage. Actually, there is plenty of water available,
but it is neither cheap nor free. For example, the
Susquehanna River could easily supply all the water
needed by 100,000,000 people, even if none of the water
returned to the river for re-use. Some sections of the
United States, however, do have a genuine water
shortage. This is especially true of the Great American
Desert, which covers most of the western United States.
In these states, the limited amount of water greatly limits
the number of people and industries in any one region.

For more than 50 years, the Department of the Inte-
rior has been constructing great storage and transporta-
tion systems to conserve the water supplies of the United
States. But large quantities of water still flowdown to



the sea without being used. See Conserv.\tion (Water
Conservation).

History

About 2000 B.C., persons in India filtered water
through charcoal, kept it in copper containers, and
exposed it to sunlight. In ancient times, people around
the Mediterranean Sea knew how to dig wells and to
collect water in cisterns. They also knew how to treat
the water to make it taste better, as well as to make it
safer to drink. Rome was the first city to have a fairly
complete water-supply system. It depended on nine
aquaducts that were from 10 to 50 miles long.

In 1829, the Chelsea Water Company built the first
water filters for the city of London. In 1871, Pough-
keepsie, N.Y., became the first large United States city
to use filters in processing its water supply. But most
cities still did not disinfect their water. About half the
population still had typhoid fever at some time in their
lives. After 1900, it became an accepted practice to
disinfect water. During the next 25 years, typhoid
fever disappeared almost completely from the United

States. John C. Geyer

Related Articles in World Book include:



Aqueduct Hydraulics


Sewage


Artesian Well Irrigation


Standpipe


Chlorire Plumbing


Water


Dam Pump


Water Meter


Filter Reservoir


Water Softening


Fluoridation Sea Water,


Well


Ground Water Purification


of


Outline




1. ScMrces of a Water Supply




A. Rain Water


D. Surface Water


B. Underground Water


E. Sea Water


C. Ground Water


F. Stored Water


II. How Water Is Purified




A. Coagulation and


D. Softening


Sedimentation


E. Other Methods


B. Filtration


of Purification


C. Disinfection




III. Distributing Water




IV. Conserving tlie Water Supply





V. History



Questions



Why do we need water supplies?

What is a cistern? .\ basin?

How do cities conserve and store water?

What is a water tabic?

What is soft water?

What do we mean by fnire drinking water?

How is chlorine used to help purify water?

What is filtration?

What is the function o(floc in purifying water?



IIO



WATER TABLE. See Drainage; Ground Water.

WATER TOWER. See Standpipe.

WATER TURBINE. See Turbine (Water Turbines).

WATER TURKEY. See Darter (bird).

WATER-VASCULAR SYSTEM. See Echinoderm.

WATER WHEEL changes tlie energy of falling water
into mechanical energy- which can be used for running
machinery. The best source of water power in nature is
found in waterfalls and rapids in rivers. The water is
directed into the wheel through a chute. The wheel is
mounted on an axle, which is connected by belts or
gearing with the machinery it is to operate. The wheel
has manv curved blades. The force with which the
water strikes the blades causes the wheel to rotate,
\\ hich makes the shaft turn. This rotates the shaft of the
machinery being dri\en.

There are two main types of water wheels, the verti-
cal and the horizontal. The vertical wheels include the
two most familiar types, the overshot and the undershot.
The amount of work which an overshot water wheel can
do is controlled by the weight and distance of the water
that falls on the wheel.

The overshot water wheel has many buckets around
its edge. The weight of the water falling into these buck-
ets causes the wheel to turn. The efficiency of this type
of water wheel sometimes reaches 80 per cent.

The undershot water wheel is built so the water
strikes against the buckets of the wheel at the bottom.
This type of wheel has such a low efficiency that it is
rarely used.

Historians believe that the first water wheel was
developed in the lOO's B.C. At that time it was used
mainly to grind com. Later it was used for many kinds
of mechanical operations. The water wheel was a major
source of power until the invention of the steam engine

in the 1700"s. Robert F. Paton

See also Hydraulics; Turbine (Water Turbines);
Water Power.




This Old Overshot Water Wheel in West Virginia is still
in use more than 1 50 years after it was first put into service.



WATERFALL

WATER WITCH. See Grebe.

WATER WONDERLAND. See Michigan.

WATERBUCK. Sec .Anielope (Kinds).

WATERBURY, Conn. (pop. 107,130; met. area 185,-
548; alt. 260 ft.), is known as the Brass Center of the
World. It lies on the Naugatuck River, 25 miles north
of Long Island Sound (see Connecticut [color map]).

Waterbury ranks first among the cities of die L'nited
States in the manufacture of brass and copper goods,
brass casting, sheet and rolled brass, and other brass-
ware products. Waterbury mills make the "blanks" for
L'nited States nickels and the coins for many South
American countries. Other products include buttons,
clocks, and foundry and machine-shop products.

People from nearby Farmington bought the \\'ater-
bury area from Indians in 1674. They established a
frontier outpost called Mattaluck. The name became
Waterbury when the town was incorporated in 1686.
The manufacture of brass goods began in 1802. Water-
bun' received its city charter in 1853. It has a mayor-
council type of government. albert e. Van dusen

WATERED STOCK. See .Stock, Capital.

WATERFALL is any sudden descent of a stream from a
higher to a lower level. In wearing down its channel, a
river uncovers certain layei-s of rock that are softer than
others. If the hard rock is farther upstream than the soft,
the channel below is worn more rapidly, and a waterfall
results. Sometimes the hard ledge forms the edge of a
vertical cliff, over which the water plunges.

If the volume of water is small, the fall may be called
a cascade. If the volume of water is large, a fall of this
sort is called a cataract. Niagara Falls is such a cataract.
Other noted cataracts are \'ictoria Falls on the Zam-
bezi River in Africa, the Falls of the Iguagu near the
Parana River in .South America, and the Grand Falls
of the Hamilton River in Labrador. Usually, however,



Online LibraryField Enterprises Educational CorporationThe World book encyclopedia (Volume 20) → online text (page 22 of 103)