The Flow of Fresh Water Chapter 11

Rivers: Agents of Erosion Many years ago there was a vast plain in the southwestern U.S. Many years ago there was a vast plain in the southwestern U.S. Over the years the Colorado River cut out the Grand Canyon Over the years the Colorado River cut out the Grand Canyon This was done by erosion. This was done by erosion.

Grand Canyon

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

Erosion can be caused by: Wind Wind Rain Rain Ice Ice Snow Snow

Wind

Rain

Ice

Snow

The Water Cycle The continuous movement of water from the ocean, to the air, to the land, then back to the ocean. The continuous movement of water from the ocean, to the air, to the land, then back to the ocean.

Some Water Cycle Words to know: Evaporation: When water from oceans, lakes, and other places on Earth’s surface turns in to water vapor and rises into the atmosphere. Evaporation: When water from oceans, lakes, and other places on Earth’s surface turns in to water vapor and rises into the atmosphere. Condensation: When water vapor cools and changes into water droplets that form clouds Condensation: When water vapor cools and changes into water droplets that form clouds

More Words Precipitation: When rain, sleet or snow falls to the Earth. Precipitation: When rain, sleet or snow falls to the Earth. Percolation: When water moves through pores in the earth’s surface into the ground Percolation: When water moves through pores in the earth’s surface into the ground Runoff: Precipitation that flows over land into streams and rivers. This water later enters oceans. Runoff: Precipitation that flows over land into streams and rivers. This water later enters oceans.

Now you try! On the next slide, label all of the words below. Evaporation Evaporation Condensation Condensation Percolation Percolation Runoff Runoff Precipitation Precipitation

Condensation Evaporation Precipitation PercolationRunoff

Think about it! How does the water cycle help develop river systems? How does the water cycle help develop river systems?

Think about it! How does the water cycle help develop river systems? How does the water cycle help develop river systems? –The water cycle causes continuous movement of water between the Earth’s surface and the atmosphere. The flow of water to the oceans creates river systems.

River Systems A tributary is a small stream that flows into a lake, or a larger stream. A tributary is a small stream that flows into a lake, or a larger stream.

Watershed A watershed is an area of land that is drained by a water system. A watershed is an area of land that is drained by a water system. –The largest in the U.S. is the Mississippi Watershed.

Think about it! Which of the following drains a watershed? Which of the following drains a watershed? –a. A divide –b. A drainage basin –c. A tributary –d. A water system

Other Watersheds Columbia Columbia Rio Grande Rio Grande Colorado Colorado

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

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

Channel A channel is the path that a stream follows. A channel is the path that a stream follows. A new stream will have a narrow, steep channel. A new stream will have a narrow, steep channel. An older stream will have a wider, and deeper channel. An older stream will have a wider, and deeper channel.

The Ability to Erode Gradient: Measure of change in elevation over a certain distance Gradient: Measure of change in elevation over a certain distance Discharge: The amount of water a stream or river carries Discharge: The amount of water a stream or river carries Load: The material carried by a stream Load: The material carried by a stream

Gradient The steeper a stream is the more erosive energy it has The steeper a stream is the more erosive energy it has

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

Load Load: the materials carried by a stream. The size of a stream’s load is affected by the stream’s speed.. Load: the materials carried by a stream. The size of a stream’s load is affected by the stream’s speed.. –Fast = large particles –Slow = Smaller particles

Think about it! What are three factors that affect the rate of stream erosion? What are three factors that affect the rate of stream erosion?

Think about it! What are three factors that affect the rate of stream erosion? What are three factors that affect the rate of stream erosion? –Gradient, Discharge, and Load

Stages of a River Rivers go through a “life cycle.” Rivers go through a “life cycle.” Youthful Youthful Mature Mature Old Old

Youthful Youthful rivers have a steep gradient, a steep and narrow channel, and many waterfalls. The channel will erode deeper, rather than wider. Youthful rivers have a steep gradient, a steep and narrow channel, and many waterfalls. The channel will erode deeper, rather than wider. Ex: Yellowstone River in Yellowstone National Park, Wyoming Ex: Yellowstone River in Yellowstone National Park, Wyoming

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

Old Old rivers have a low gradient and little erosive energy. They deposit rather than erode. Old rivers have a low gradient and little erosive energy. They deposit rather than erode. Do you think Old Rivers would contribute to flooding in an area? Do you think Old Rivers would contribute to flooding in an area?

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

Think about it! Which stage of river development is characterized by flat flood plains? Which stage of river development is characterized by flat flood plains?

Think about it! Which stage of river development is characterized by flat flood plains? Which stage of river development is characterized by flat flood plains? –Old rivers