The Flow of Fresh WaterThe Flow of Fresh Water

Chapter 11Chapter 11

Rivers: Agents of ErosionRivers: Agents of Erosion• Many years ago there was a vast Many years ago there was a vast

plain in the southwestern U.S.plain in the southwestern U.S.

• Over the years the Colorado River Over the years the Colorado River cut out the Grand Canyoncut out the Grand Canyon

• This was done by erosion.This was done by erosion.

Grand CanyonGrand Canyon

Grand CanyonGrand Canyon

Grand CanyonGrand Canyon

ErosionErosion

• The process by which soil and The process by which soil and sediment are transported from one sediment are transported from one location to another.location to another.

Erosion can be caused by:Erosion can be caused by:

• WindWind

• RainRain• IceIce

• SnowSnow

WindWind

RainRain

IceIce

SnowSnow

The Water CycleThe Water Cycle• The continuous movement of water The continuous movement of water

from the ocean, to the air, to the from the ocean, to the air, to the land, then back to the ocean.land, then back to the ocean.

Some Water Cycle Words to Some Water Cycle Words to know:know:

• EvaporationEvaporation: When water from : When water from oceans, lakes, and other places on oceans, lakes, and other places on Earth’s surface turns in to water Earth’s surface turns in to water vapor and rises into the atmosphere.vapor and rises into the atmosphere.

• CondensationCondensation: When water vapor : When water vapor cools and changes into water cools and changes into water droplets that form cloudsdroplets that form clouds

More WordsMore Words• PrecipitationPrecipitation: When rain, sleet or snow falls : When rain, sleet or snow falls

to the Earth.to the Earth.

• PercolationPercolation: When water moves through : When water moves through pores in the earth’s surface into the groundpores in the earth’s surface into the ground

• RunoffRunoff: Water that flows over land into : Water that flows over land into lakes, seas, or oceans.lakes, seas, or oceans.

• Water that flows over land into lakes, seas, Water that flows over land into lakes, seas, or oceans.or oceans.

Now you try!Now you try!

On the next slide, label all of the words On the next slide, label all of the words below.below.

• EvaporationEvaporation

• CondensationCondensation

• PercolationPercolation

• RunoffRunoff

• PrecipitationPrecipitation

River SystemsRiver Systems• A A tributarytributary is a small stream that is a small stream that

flows into a lake, or a larger stream.flows into a lake, or a larger stream.

WatershedWatershed• A watershed is an area of land that is A watershed is an area of land that is

drained by a water system.drained by a water system.– The largest in the U.S. is the Mississippi The largest in the U.S. is the Mississippi

Watershed.Watershed.

Other WatershedsOther Watersheds• ColumbiaColumbia

• Rio GrandeRio Grande

• ColoradoColorado

DivideDivide

• A divide is an area of higher ground A divide is an area of higher ground that separates water sheds from that separates water sheds from each other.each other.

How does this divide separate How does this divide separate the U.S. and its watersheds?the U.S. and its watersheds?

ChannelChannel • A A channelchannel is the path that a stream is the path that a stream

follows.follows.

• A new stream will have a narrow, A new stream will have a narrow, steep channel.steep channel.

• An older stream will have a wider, An older stream will have a wider, and deeper channel.and deeper channel.

The Ability to ErodeThe Ability to Erode

• GradientGradient: Measure of change in : Measure of change in elevation over a certain distanceelevation over a certain distance

• DischargeDischarge: The amount of water a : The amount of water a stream or river carriesstream or river carries

• LoadLoad: The material carried by a stream: The material carried by a stream

GradientGradient

• The steeper a stream is the more The steeper a stream is the more erosive energy it haserosive energy it has

DischargeDischarge

• The more water a river will discharge The more water a river will discharge the more erosive power it will have.the more erosive power it will have.

LoadLoad

• Load is affected by speed.Load is affected by speed.

– Fast = large particlesFast = large particles– Slow = Smaller particlesSlow = Smaller particles

Stages of a RiverStages of a River

• Rivers go through a “life cycle.”Rivers go through a “life cycle.”

• YouthfulYouthful

• MatureMature

• OldOld

YouthfulYouthful• Youthful riversYouthful rivers have a steep gradient, have a steep gradient,

a steep and narrow channel, and a steep and narrow channel, and many waterfalls. The channel will many waterfalls. The channel will erode deeper, rather than wider.erode deeper, rather than wider.

MatureMature

• Mature Rivers Mature Rivers have a gradient that is have a gradient that is not as steep as a youthful river. They not as steep as a youthful river. They have few falls and rapids. They will have few falls and rapids. They will erode wider rather than deeper.erode wider rather than deeper.

OldOld

• Old rivers have a low gradient and Old rivers have a low gradient and little erosive energy. They deposit little erosive energy. They deposit rather than erode.rather than erode.

Rejuvenated RiversRejuvenated Rivers

• Rejuvenated rivers are mature rivers Rejuvenated rivers are mature rivers that have a steeper gradient due to that have a steeper gradient due to land rising because of tectonic land rising because of tectonic activity.activity.