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Key.

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Water is essential to every living thing.

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All those that need a continuous supply
of water in order to live in food making

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and in other life processes
land water derives from rain

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roughly one third of all rainfall runs
off into streams rivers and lakes

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and these constitute our chief surface water
supply about one third soaks into the

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ground

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and becomes our underground water part
of the rain is used up by dense forests

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which require about
twenty inches annually.

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While grasslands prevail where the
rainfall is between ten and thirty inches

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that desert is a sign of meager rainfall
life here is greatly restricted

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rainfall is unequally
distributed with the result

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that we find Navy forests in the West
and East grounds in the central states

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and spines

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and desert plants in the Southwest
to exist man requires a

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continuous supply of water springs furnish

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and accessible a limited source underground
water may also be tapped by Wells such

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as this old it done. Well

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and sweep many large cities at the
same located here by dots depend upon

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underground water tapped by
modern wells for other cities.

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The surface water taken from reveries
constitutes the only adequate

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and available source. Some cities
take their water from nearby lakes.

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Surface water is our own so made available
to certain cities by impounding the

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headwaters of rivers by dams.

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America's largest city depends mainly on
watershed for its water supply New York

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City needs one billion gallons of water
daily an amount about equal to the flow in

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this river wells and cisterns
originally used became inadequate

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and about a century ago the city started
to develop the Croton watershed fifty

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miles away the water was carried by an
aqueduct here crossing the Harlem River

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the continued growth of the city's soonest
as it dated additional water supplies.

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Then a watershed was utilized in the
Catskill Mountains one hundred miles away in

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this watershed the runoff in streams is
impounded by a dam with associated dykes

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and wearies to form a reservoir later a
second watershed was developed on the

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northern slope of the Catskills by
constructing a dam to impound its water from

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this reservoir a tunnel eighteen miles
long passes under the dividing mountains

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and discharges its water into a creek which
flows into the reservoir on the south

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slope from this Catskills system water
enters an aqueduct then continues on through

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this aqueduct for about seventy
miles to an intermediate reservoir.

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Through the greater portion of this
distance the aqueduct is a cut to cover

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construction about seventeen
feet in diameter grade

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tunnels carry the water through obstructing
mountains to underpass the majestic

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Hudson River a pressure tunnel sinks up
thousand feet through the underlying rock.

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This enormous problem required extensive
cooperative work by geologists engineers

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and other experts in the
tunnel construction.

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Cutting through solid rock hundreds of
feet underground as shown here is only one

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of the many problems in
constructing an accident.

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Because of the difference in elevation
gravity provides sufficient pressure to

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transport the water from the Catskill
reservoirs to the Canseco intermediate

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reservoir the great bulk of this
water remains in this reservoir.

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What about one month from here.

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It flows to a small equalizing reservoir
which takes care of our early demand

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fluctuations with increasing population

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and water consumption New York City has
been compelled to provide the Delaware

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system consisting of three separate
watersheds still farther away.

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This has necessitated the
construction of a new aqueduct

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that finally connects with the original
system represented here is the watershed

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system utilized by America's largest city

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just as important as an adequate water
supply is a safe water supply municipal

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sewage treatment plants reduce
pollution caused by sewage

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and industrial waste time third fever is
one disease commonly carried by water in

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one city the installation of sand filters
in the practice of chlorination was

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followed by a marked decrease in the
number of times forward fever cases until

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today this disease is very rare where
scientific controls are employed

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the laboratory occupies a key position in
safeguarding the city water supply water

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samples are collected daily
one test known as up.

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Mentation test indicates the
presence of contamination.

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Furthermore the water is examined for
microscopic organisms many of these organisms

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impart specific odors and
tastes to the water.

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But certain bacteria cannot easily
be detected under the microscope.

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Therefore a measured amount
of water is placed in a dish

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and the sterilized culture medium is
added in makes this is then placed in an

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integrator for one

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or two days in this culture medium each
bacterium has now multiplied into a

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colony that is easily detected
these colonies can now be counted

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or examined under a microscope
for identification.

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The water is also examined chemical A
for the presence of foreign substances

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that may affect its palatability or
if used in industry in the home.

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The presence of ammonia nitrogen
indicates organic decay

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and is determined by an elaborate test
involving distillation an indicator

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that intensity of tensed is
revealed in the color Ramit

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or gives a measure of the amount of
nitrogen in the original water sample

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most surface waters pick
up fine particles of clay

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or soil causing tribute at the this is
tested with a candle at the bottom of a

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cylinder.

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The water sample is poured in until the
target of the obscures the light of the

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candle.

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When water stands we have been for
some time as in the lake or reservoir.

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However much of this suspended matter settles
out to speed up the settling process

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alum is often added to the water this
forms of flaky precipitate which

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settles out carrying with
it. Much of the suspend.

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Material

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and bacteria since alum makes
water acid in corrosive lime is

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added to render the water
slightly alkaline many cities use

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filter beds of sand to
remove that solid matter.

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This site well eight feet deep indicates
the clearness of the water after treatment

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that is more and more mix activated
carbon to the water to remove color odor

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and taste a aeration is another
common method of removing odors

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and increasing palatability of drinking
water the final step in water treatment

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involves adding chlorine This completes
the sterilization by destroying all the

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harmful bacteria

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and other organisms in New York
City water already made pure

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and safe

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and is the city through two huge tunnels
real through solid rock about two hundred

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feet underground risers bring the
water up near to the surface

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the water flows from the risers to connecting
mains then into lateral street names

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and finally through service connections
into each building on the street.

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The higher elevation of the reservoir causes
water to flow into the city by gravity.

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However some consumption points
are higher than the source

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and pumps must be used many high buildings
have their own pumps to maintain a

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sufficient water pressure
to the top floors.

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The water that's provided has many uses it
flows through thousands of safe drinking

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fountains.

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It is used in the cooking of many of
our food and laundering our clothing

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and in other ways water contributes
to cleanliness send help.

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Water is used in generating steam for heating
building water AIDS in defending the

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city's health by slashing our streets

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and by carrying away sewage clean water
plays an important role in healthful

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recreation water also is an essential
part of the composition of beautiful

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fountains the control of this stuff the
fires requires water sometimes in great

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amount without which man cannot
live must be supplied in abundance

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and with safety to a sure healthful
living in a modern city.