Our Water SupplyOur Water Supply

01.03.08 / 01.04.0801.03.08 / 01.04.08

Water CycleWater Cyclewater cyclewater cycle the continuous movement of water the continuous movement of water

between the atmosphere, the land, and the between the atmosphere, the land, and the oceansoceans

• More than 2/3 of Earth’s surface is covered More than 2/3 of Earth’s surface is covered with water.with water.

• In the atmosphere, water occurs as an In the atmosphere, water occurs as an invisible gas. This gas is called invisible gas. This gas is called water vaporwater vapor. . Liquid water also exists in the atmosphere as Liquid water also exists in the atmosphere as small particles in clouds and fog.small particles in clouds and fog.

• Earth’s water is constantly changing from one Earth’s water is constantly changing from one form to another.form to another.

Earth’s Water SupplyEarth’s Water Supply

Water CycleWater Cycleevapotranspirationevapotranspiration the total loss of water the total loss of water

from an area, which equals the sum of the from an area, which equals the sum of the water lost by evaporation from the soil and water lost by evaporation from the soil and other surfaces and the water lost by other surfaces and the water lost by transpiration from organisms transpiration from organisms

• Each year, about 500,000 kmEach year, about 500,000 km33 of water of water evaporates into the atmosphere. About 86% evaporates into the atmosphere. About 86% of this water evaporates from the ocean.of this water evaporates from the ocean.

• Water vapor also enters the air by Water vapor also enters the air by transpirationtranspiration, the process by which plants and , the process by which plants and animals release water vapor into the animals release water vapor into the atmosphere.atmosphere.

Water CycleWater Cyclecondensationcondensation the change of state from the change of state from

a gas to a liquida gas to a liquid

• When water vapor rises in the When water vapor rises in the atmosphere, it expands and cools.atmosphere, it expands and cools.

• As the vapor becomes cooler; some of As the vapor becomes cooler; some of it condenses, or changes into tiny it condenses, or changes into tiny liquid water droplets, and forms liquid water droplets, and forms clouds.clouds.

Water CycleWater Cycleprecipitationprecipitation any form of water that falls to any form of water that falls to

Earth’s surface from the clouds; includes Earth’s surface from the clouds; includes rain, snow, sleet, and hailrain, snow, sleet, and hail

• About 75% of all precipitation falls on About 75% of all precipitation falls on Earth’s oceans. The rest falls on land and Earth’s oceans. The rest falls on land and becomes becomes runoffrunoff or or groundwatergroundwater..

• Eventually, all of this water returns to the Eventually, all of this water returns to the atmosphere by evapotranspiration, atmosphere by evapotranspiration, condenses, and falls back to Earth’s condenses, and falls back to Earth’s surface to begin the cycle again.surface to begin the cycle again.

Water CycleWater Cycle

Water BudgetWater Budget• In Earth’s water budget, precipitation is In Earth’s water budget, precipitation is

the the incomeincome. Evapotranspiration and runoff . Evapotranspiration and runoff are the are the expensesexpenses..

• The water budget of Earth as a whole is The water budget of Earth as a whole is balanced because the amount of balanced because the amount of precipitation is equal to the amount of precipitation is equal to the amount of evapotranspiration and runoff.evapotranspiration and runoff.

• However, the water budget of a particular However, the water budget of a particular area, called the area, called the local water budgetlocal water budget, is , is usually not balanced.usually not balanced.

Water BudgetWater BudgetFactors That Affect the Water BudgetFactors That Affect the Water Budget

• Factors that affect the local water Factors that affect the local water budget include temperature, vegetation, budget include temperature, vegetation, wind, and the amount and duration of wind, and the amount and duration of rainfall.rainfall.

• The factors that affect the local water The factors that affect the local water budget vary geographically.budget vary geographically.

• The local water budget also changes The local water budget also changes with the seasons in most areas of Earth.with the seasons in most areas of Earth.

Water BudgetWater BudgetWater UseWater Use

• On average, each person in the United States On average, each person in the United States uses about 20,890 gal of water each year.uses about 20,890 gal of water each year.

• As the population of the United States As the population of the United States increases, so does the demand for water.increases, so does the demand for water.

• About 90% of the water used by cities and About 90% of the water used by cities and industry is returned to rivers or to the oceans industry is returned to rivers or to the oceans as wastewater.as wastewater.

• Some of this wastewater contains harmful Some of this wastewater contains harmful materials, such as toxic chemicals and metals. materials, such as toxic chemicals and metals.

Water BudgetWater BudgetConservation of WaterConservation of Water

• Scientists have identified two ways to Scientists have identified two ways to ensure that enough fresh water is ensure that enough fresh water is available today and in the future.available today and in the future.

• One way is through One way is through conservationconservation, or the , or the wise use of water resources.wise use of water resources.

• A second way to protect the water supply A second way to protect the water supply is to find alternative methods of obtaining is to find alternative methods of obtaining fresh water.fresh water.

Water BudgetWater BudgetConservation of Water, continuedConservation of Water, continued

desalinationdesalination a process of removing salt a process of removing salt from ocean waterfrom ocean water

• Desalination is expensive and is impractical Desalination is expensive and is impractical for supplying water to large populations.for supplying water to large populations.

• Currently, the best way of maintaining an Currently, the best way of maintaining an adequate supply of fresh water is the wise adequate supply of fresh water is the wise use and conservation of the fresh water use and conservation of the fresh water that is now available.that is now available.

ConservationConservation

• Voluntary conservation costs nothing – Voluntary conservation costs nothing – in fact, it can save moneyin fact, it can save money

• Some conservation methods can be Some conservation methods can be enforced by lawenforced by law– Florida has water restrictionsFlorida has water restrictions– Congress limited the water used by toiletsCongress limited the water used by toilets– These methods cost money to implement These methods cost money to implement

and enforceand enforce

Household Water UsageHousehold Water Usage

ConservationConservation• A front-loading washer uses 10-15 A front-loading washer uses 10-15

gal per load, while a top-loading gal per load, while a top-loading washer uses about 40 gal per load. washer uses about 40 gal per load.

ConservationConservation• XeriscapingXeriscaping landscaping that does landscaping that does

not require artificial wateringnot require artificial watering

BadGood

Bad

Florida Yards and Neighborhoods

Program

Good

Stormwater RunoffStormwater Runoff

Porous surfaces Porous surfaces allow water to allow water to soak into the soak into the ground; solid ground; solid surfaces, such surfaces, such as concrete as concrete cause more cause more evaporation evaporation and can push and can push pollutants into pollutants into river systemsriver systems

Florida Florida Aquarium Aquarium ExperimentExperimental Parking al Parking LotLot

River SystemsRiver Systemstributariestributaries streams that flows into a lake or streams that flows into a lake or

into a larger streaminto a larger stream

watershed (AKA basin)watershed (AKA basin) the area of land the area of land that is drained by a river system that is drained by a river system

• A river system is made up of a main A river system is made up of a main stream and tributaries.stream and tributaries.

• The ridges or elevated regions that The ridges or elevated regions that separate watersheds are calledseparate watersheds are called dividesdivides..

Continental DividesContinental Divides

Mississippi River BasinMississippi River Basin

Peace River Peace River WatershedWatershed

River SystemsRiver Systems• The relatively narrow depression that a The relatively narrow depression that a

stream follows as it flows downhill is called its stream follows as it flows downhill is called its channelchannel..

• The edges of a stream channel that are above The edges of a stream channel that are above water level are called the stream’s water level are called the stream’s banksbanks..

• The part of the stream channel that is below The part of the stream channel that is below the water level is called the stream’s the water level is called the stream’s bedbed..

• A stream channel gradually becomes wider A stream channel gradually becomes wider and deeper as it erodes its banks and bed.and deeper as it erodes its banks and bed.

River SystemsRiver Systems• River systems change continuously River systems change continuously

because of erosion.because of erosion.

• In the process of In the process of headward headward erosionerosion, channels lengthen and , channels lengthen and branch out at their upper ends, branch out at their upper ends, where run off enters the streams.where run off enters the streams.

River SystemsRiver Systemsstream loadstream load the materials other than the the materials other than the

water that are carried by a streamwater that are carried by a stream

• A stream transports soil, loose rock A stream transports soil, loose rock fragments, and dissolved mineral as it fragments, and dissolved mineral as it flows downhill.flows downhill.

• Stream load takes three forms: Stream load takes three forms: suspended load, bed load, and dissolved suspended load, bed load, and dissolved load.load.

Stream LoadStream Load

River SystemsRiver SystemsStream LoadStream Load, continued, continued

• The The suspended loadsuspended load consists of particles of fine consists of particles of fine sand and silt. The velocity, or rate of downstream sand and silt. The velocity, or rate of downstream travel, of the water keeps these particles travel, of the water keeps these particles suspended, so they do not sink to the stream bed.suspended, so they do not sink to the stream bed.

• The The bed loadbed load is made up of larger, coarser is made up of larger, coarser materials, such as coarse sand, gravel, and materials, such as coarse sand, gravel, and pebbles. This material moves by sliding and pebbles. This material moves by sliding and jumping along the bed.jumping along the bed.

• The The dissolved loaddissolved load is mineral matter is mineral matter transported in liquid solution.transported in liquid solution.

River SystemsRiver SystemsStream dischargeStream discharge the volume of water the volume of water

that flows within a given time, expressed that flows within a given time, expressed in min m33 or ft/sec or ft/sec

• The faster a stream flows, the higher its The faster a stream flows, the higher its discharge and the greater the load that discharge and the greater the load that the stream can carry.the stream can carry.

• A stream’s velocity also affects how the A stream’s velocity also affects how the stream cuts down and widens its channel. stream cuts down and widens its channel. Swift streams erode their channels more Swift streams erode their channels more quickly than slow-moving streams do.quickly than slow-moving streams do.

River SystemsRiver Systems

River SystemsRiver SystemsStream gradientStream gradient the change in elevation the change in elevation

over a given distanceover a given distance

• Near the Near the headwatersheadwaters, or the beginning of , or the beginning of a stream, the gradient generally is steep. a stream, the gradient generally is steep. This area of the stream has a high velocity, This area of the stream has a high velocity, which causes rapid channel erosion.which causes rapid channel erosion.

• As the stream nears its As the stream nears its mouthmouth, where the , where the stream enters a larger body of water, its stream enters a larger body of water, its gradient often becomes flatter. gradient often becomes flatter.

GradientGradient

River SystemsRiver Systems

Evolution of ChannelsEvolution of Channelsmeandermeander one of the bends, twists, or curves one of the bends, twists, or curves

in a low-gradient stream or riverin a low-gradient stream or river

• When a river rounds a bend, the velocity When a river rounds a bend, the velocity of the water on the outside of the curve of the water on the outside of the curve increase. However, on the inside of the increase. However, on the inside of the curve, the velocity of the water decreases. curve, the velocity of the water decreases. (ex. marching band)(ex. marching band)

• This decrease in velocity leads to the This decrease in velocity leads to the formation of a formation of a barbar of deposited sediment, of deposited sediment, such as sand or gravel.such as sand or gravel.

Stream FlowStream Flow

Evolution of ChannelsEvolution of ChannelsMeandering Channels, Meandering Channels, continuedcontinued

• As this process continues, the curve As this process continues, the curve enlarges while further erosion takes enlarges while further erosion takes place on the opposite bank, where the place on the opposite bank, where the water is moving more quickly.water is moving more quickly.

• Meanders can become so curved that Meanders can become so curved that they almost form a loop, separated by they almost form a loop, separated by only a narrow neck of land.only a narrow neck of land.

HorseshoeHorseshoeBendBendof the Colorado River of the Colorado River near Page, AZnear Page, AZ

Evolution of ChannelsEvolution of ChannelsBraided streamBraided stream a stream or river that is a stream or river that is

composed of multiple channels that divide composed of multiple channels that divide and rejoin around sediment barsand rejoin around sediment bars

• Braided streams are a direct result of large Braided streams are a direct result of large sediment load, particularly when a high sediment load, particularly when a high percentage of the load is composed of percentage of the load is composed of coarse sand and gravel.coarse sand and gravel.

• Although braided streams look very Although braided streams look very different from meandering streams, they different from meandering streams, they can cause just as much erosion.can cause just as much erosion.

Braided StreamBraided Stream

Deltas and Alluvial FansDeltas and Alluvial Fansdeltadelta a fan-shaped mass of rock material a fan-shaped mass of rock material

deposited at the mouth of a stream; for deposited at the mouth of a stream; for example, deltas form where streams flow example, deltas form where streams flow into the ocean at the edge of a continentinto the ocean at the edge of a continent

• A stream may deposit sediment on land or in A stream may deposit sediment on land or in water.water.

• The exact shape and size of a delta are The exact shape and size of a delta are determined by waves, tides, offshore depths, determined by waves, tides, offshore depths, and the sediment load of the stream.and the sediment load of the stream.

Deltas and Alluvial FansDeltas and Alluvial Fansalluvial fanalluvial fan a fan-shaped mass of rock material a fan-shaped mass of rock material

deposited by a stream when the slope of the land deposited by a stream when the slope of the land decreases sharply; for example, alluvial fans form decreases sharply; for example, alluvial fans form when streams flow from mountains to flat landwhen streams flow from mountains to flat land

• When a stream descends a steep slope and When a stream descends a steep slope and reaches a flat plain, the speed of the stream reaches a flat plain, the speed of the stream suddenly decreases. As a result, the stream suddenly decreases. As a result, the stream deposits some of its load on the level plain at the deposits some of its load on the level plain at the base of the slope.base of the slope.

• Alluvial fans differ from deltas in that alluvial fans Alluvial fans differ from deltas in that alluvial fans form on land instead of being deposited in water.form on land instead of being deposited in water.

FloodplainsFloodplainsfloodplainfloodplain an area along a river that an area along a river that

forms from sediments deposited forms from sediments deposited when the river overflows its bankswhen the river overflows its banks

• The volume of water in nearly all The volume of water in nearly all streams varies depending on the streams varies depending on the amount of rainfall and snowmelt in amount of rainfall and snowmelt in the watershed.the watershed.

FloodplainsFloodplains

FloodplainsFloodplainsNatural LeveesNatural Levees

• When a stream overflows its banks and When a stream overflows its banks and spreads out over the floodplain, the spreads out over the floodplain, the stream loses velocity and deposits its stream loses velocity and deposits its coarser sediment load along the banks of coarser sediment load along the banks of the channel.the channel.

• The accumulation of these deposits along The accumulation of these deposits along the banks eventually produces raised the banks eventually produces raised banks, called banks, called natural leveesnatural levees..

Natural LeveesNatural Levees

Human ActivityHuman Activity• Human activity can contribute to the size Human activity can contribute to the size

and number of floods in many areas.and number of floods in many areas.

• Vegetation, such as trees and grass, Vegetation, such as trees and grass, protects the ground surface from erosion by protects the ground surface from erosion by taking in much of the water that would taking in much of the water that would otherwise run off. otherwise run off.

• Logging and the clearing of land for Logging and the clearing of land for agriculture or housing development can agriculture or housing development can increase the volume and speed of runoff, increase the volume and speed of runoff, which leads to more frequent flooding.which leads to more frequent flooding.

Human ActivityHuman Activity• Indirect methods of flood control include Indirect methods of flood control include

forest and soil conservation measures that forest and soil conservation measures that prevent excess runoff during periods of heavy prevent excess runoff during periods of heavy rainfall.rainfall.

• More-direct methods include the building of More-direct methods include the building of artificial structures that redirect the flow of artificial structures that redirect the flow of water.water.

• The most common method of direct flood The most common method of direct flood control is the building of control is the building of damsdams. Another direct . Another direct method of flood control is the building of method of flood control is the building of artificial leveesartificial levees..

New Orleans New Orleans LeveesLevees

Life Cycle of LakesLife Cycle of Lakes• Most lakes are relatively short lived in Most lakes are relatively short lived in

geologic terms.geologic terms.

• Many lakes eventually disappear because Many lakes eventually disappear because too much of their water drains away or too much of their water drains away or evaporates.evaporates.

• Lake basins may also disappear if they fill Lake basins may also disappear if they fill with sediments. Streams that feed a lake with sediments. Streams that feed a lake deposit sediments in the lake. The lake deposit sediments in the lake. The lake basin may eventually become dry land.basin may eventually become dry land.

World Watershed Sediment World Watershed Sediment YieldYield

Kermit says being green is cool.Kermit says being green is cool.

So conserve your water.So conserve your water.