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Chapter 6:  Freshwater at    Earth’s Surface Table of Contents Section 3:  Wetlands Section 1:  Streams Section 2:  Lakes ...
<ul><li>Water is  essential  for life.  </li></ul><ul><li>Plants use water , along with carbon dioxide, to make food with ...
<ul><li>Freshwater at Earth’s surface is a minute fraction of all the water on the planet.  </li></ul><ul><li>If 1 L of wa...
<ul><li>The water that doesn’t sink in, but instead runs across Earth’s surface, is   runoff .  </li></ul><ul><li>As water...
<ul><li>All streams shape Earth’s surface.  </li></ul><ul><li>Water flowing  over Earth’s surface  erodes  the land by wea...
<ul><li>Streams that have channels with many curves are called   meandering streams .  </li></ul><ul><li>Rivers that meand...
<ul><li>Water on the  outside of a bend , or meander, is  deeper and flows faster , so it  erodes the bank of the stream ....
<ul><li>Meandering streams are  always changing .  </li></ul><ul><li>Erosion on the outside of a meander and deposition of...
<ul><li>Eroded sediment, such as sand and gravel, can be deposited in the middle of a stream channel, forming bars.  </li>...
<ul><li>Because of gravity, water falling on Earth’s surface flows downhill until it reaches the lowest level that it can ...
<ul><li>Large rivers, like the Mississippi, can have huge drainage basins that include many smaller streams.  </li></ul>Dr...
1 Streams Local Drainage Basins
Local Drainage Basins 1 Streams
Local Drainage Basins 1 Streams
 
Local Drainage Basins 1 Streams
Drainage Basins So where do we drain you ask?
<ul><li>An elevated area of land called a divide separates the drainage basin of one stream from the drainage basin of ano...
1 Streams
1 Eastern Continental Divide
<ul><li>Streams remove rock and sediment from some places and transport it to other places.  </li></ul><ul><li>Streams ero...
<ul><li>The faster the water flows, the more sediment a stream moves.  </li></ul><ul><li>The sediment that is moved by the...
<ul><li>Sediment that is carried by a stream is called stream   load .  </li></ul><ul><li>The  three different types of st...
<ul><li>Sediment that moves along the bed of a stream by rolling, bouncing, or sliding is the bed load. </li></ul><ul><li>...
<ul><li>Suspended load makes some streams appear to be muddy.  </li></ul><ul><li>Some rock materials become dissolved in w...
<ul><li>Sometimes the land on which a stream is located is uplifted gradually. </li></ul><ul><li>This uplifting changes th...
Video
<ul><li>When water has a lot of energy, as it does when a stream has large volumes of fast-moving water, it carries and mo...
<ul><li>Water in a stream loses energy and might deposit sediment where the streambed becomes flatter, or where the stream...
<ul><li>The deposited sediment eventually raises  the bottom of the water body, and the stream forms new channels through ...
<ul><li>When a fast-moving mountain stream flows onto a flat plain or valley, a fan-shaped deposit of sediment, called an ...
<ul><li>The volume of water flowing through a stream in a given amount of time is called  stream  discharge .  </li></ul><...
<ul><li>Heavy rain or melting ice and snow can lead to an increase in discharge. </li></ul><ul><li>As discharge increases,...
<ul><li>Sometimes a stream’s discharge increases so much that the river channel cannot hold the increased volume of water....
<ul><li>When the water overflows its banks, it spreads out over the floodplain and the speed of the water flow decreases. ...
<ul><li>One way to  control a flood  is to build  artificial levees , which are mounds of soil placed on the sides of a st...
<ul><li>Flood-control dams   store the additional stream discharge   and/or let it out a little at a time, thus preventing...
<ul><li>Stream channels can be altered to hold more water.  </li></ul><ul><li>Dredging the channel makes it deeper and str...
<ul><li>As more water moves faster, erosion of the stream banks and channel increases.  </li></ul><ul><li>Often,  trees th...
<ul><li>The best solution to flood problems is to use the land wisely.  </li></ul><ul><li>Identify areas of the floodplain...
Question 1 Section Check 1 Question 1 What three factors determine how much water runs off into stream channels? NC: 3.02
Question 2 1 Section Check Question 2 Which type of stream is shown here?  NC: 3.02
Question 3 1 Section Check Question 3 Explain how new land can be created by streams. NC: 3.02
Answer 1 Section Check 1 Question 1 What three factors determine how much water runs off into stream channels? Answer The ...
Answer 2 1 Section Check A. braided stream B. meandering stream C. straight stream D. wide stream NC: 3.02
1 Section Check Answer The answer is B. Streams that have channels with many curves are called meandering streams.  NC: 3.02
Answer 3 1 Section Check Answer When a stream empties into a lake, sediment is deposited and a delta forms. The deposited ...
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Chapter 6:1 Freshwater at Earth’s Surface - Streams

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Chapter 6:1 Freshwater at Earth’s Surface - Streams

  1. 2. Chapter 6: Freshwater at Earth’s Surface Table of Contents Section 3: Wetlands Section 1: Streams Section 2: Lakes and Reservoirs Section 4: Pollution of Freshwater
  2. 3. <ul><li>Water is essential for life. </li></ul><ul><li>Plants use water , along with carbon dioxide, to make food with the aid of sunlight. </li></ul>Where is Earth’s freshwater? 1 Streams <ul><li>Animals use water to move nutrients and wastes through their bodies. </li></ul><ul><li>Humans can survive for weeks without food, but for only a few days without freshwater. </li></ul>
  3. 4. <ul><li>Freshwater at Earth’s surface is a minute fraction of all the water on the planet. </li></ul><ul><li>If 1 L of water represents all of Earth’s water, a drop represents all the water in lakes and rivers. </li></ul>Where is Earth’s freshwater? 1 Streams
  4. 5. <ul><li>The water that doesn’t sink in, but instead runs across Earth’s surface, is runoff . </li></ul><ul><li>As water falls on Earth’s surface, runoff moves from higher to lower areas. </li></ul>Runoff 1 Streams <ul><li>Over time, the water enters small channels and eventually flows into streams . </li></ul><ul><li>The slope of the land, how much vegetation is on it, and how much it rains help determine how much water runs off into stream channels. </li></ul>
  5. 6. <ul><li>All streams shape Earth’s surface. </li></ul><ul><li>Water flowing over Earth’s surface erodes the land by wearing away rock and moving weathered rock and soil . </li></ul>Types of Streams 1 Streams <ul><li>However, a stream can erode Earth’s surface no deeper than its base level, the level of the water body that the stream flows into. </li></ul>
  6. 7. <ul><li>Streams that have channels with many curves are called meandering streams . </li></ul><ul><li>Rivers that meander usually develop on low slopes and carry a lot of fine sediment, such as silt and clay. </li></ul>Meandering Streams 1 Streams <ul><li>The water in meandering streams erodes in land in some places and deposits sediment in others . </li></ul>
  7. 8. <ul><li>Water on the outside of a bend , or meander, is deeper and flows faster , so it erodes the bank of the stream . </li></ul><ul><li>Water on the inside of a meander flows slower, so sediment gets deposited there . </li></ul>Meandering Streams 1 Streams <ul><li>Soon a point ( sand ) bar , a pile of sand and gravel that is deposited on the inside of a meander, forms. </li></ul>
  8. 9. <ul><li>Meandering streams are always changing . </li></ul><ul><li>Erosion on the outside of a meander and deposition of sediment on the inside cause the stream to move back and forth across its valley over time. </li></ul>Meandering Streams 1 Streams <ul><li>Meanders also slowly migrate down the valley. </li></ul>
  9. 10. <ul><li>Eroded sediment, such as sand and gravel, can be deposited in the middle of a stream channel, forming bars. </li></ul><ul><li>As the bars develop, water flows through many different channels. </li></ul>Braided Streams 1 Streams <ul><li>Sometimes these bars get so large that they become islands within the river. </li></ul><ul><li>Streams with many bars and islands separated by river channels are called braided streams . </li></ul>
  10. 11. <ul><li>Because of gravity, water falling on Earth’s surface flows downhill until it reaches the lowest level that it can flow to—its base level. </li></ul><ul><li>Streams transport water from higher ground to an ocean or a lake. </li></ul>Drainage Basins 1 Streams <ul><li>Each stream drains water from a specific area of Earth’s surface. </li></ul><ul><li>This area is called the stream’s drainage basin . </li></ul>
  11. 12. <ul><li>Large rivers, like the Mississippi, can have huge drainage basins that include many smaller streams. </li></ul>Drainage Basins 1 Streams
  12. 13. 1 Streams Local Drainage Basins
  13. 14. Local Drainage Basins 1 Streams
  14. 15. Local Drainage Basins 1 Streams
  15. 17. Local Drainage Basins 1 Streams
  16. 18. Drainage Basins So where do we drain you ask?
  17. 19. <ul><li>An elevated area of land called a divide separates the drainage basin of one stream from the drainage basin of another. </li></ul><ul><li>Divides can be as small as a ridge or as large as a mountain range. </li></ul>Divides 1 Streams <ul><li>An area that separates drainage basins of an entire continent is called a continental divide. </li></ul>
  18. 20. 1 Streams
  19. 21. 1 Eastern Continental Divide
  20. 22. <ul><li>Streams remove rock and sediment from some places and transport it to other places. </li></ul><ul><li>Streams erode in two important ways. </li></ul>Stream Erosion 1 Streams <ul><li>The force of the flowing water in a stream can be strong enough to move loose sediment, such as silt, sand or gravel. </li></ul>
  21. 23. <ul><li>The faster the water flows, the more sediment a stream moves. </li></ul><ul><li>The sediment that is moved by the water allows streams to erode in another way. </li></ul>Stream Erosion 1 Streams <ul><li>When the grains of sediment hit rock on the stream bottom, small pieces can be broken off of the rock and carried away. </li></ul>
  22. 24. <ul><li>Sediment that is carried by a stream is called stream load . </li></ul><ul><li>The three different types of stream load are bed load, suspended load, and dissolved load. </li></ul>Load 1 Streams
  23. 25. <ul><li>Sediment that moves along the bed of a stream by rolling, bouncing, or sliding is the bed load. </li></ul><ul><li>These are particles that are too heavy to be carried by the flowing water. </li></ul>Load 1 Streams <ul><li>When sediment is light enough to become suspended in the water, it is carried by the stream as suspended load. </li></ul>
  24. 26. <ul><li>Suspended load makes some streams appear to be muddy. </li></ul><ul><li>Some rock materials become dissolved in water and are carried in solution by the stream as dissolved load. </li></ul>Load 1 Streams <ul><li>Much of the dissolved load is carried into streams by groundwater. </li></ul>
  25. 27. <ul><li>Sometimes the land on which a stream is located is uplifted gradually. </li></ul><ul><li>This uplifting changes the distance from the stream to its base level. </li></ul>Canyon Formation 1 Streams <ul><li>The streambed becomes steeper. </li></ul><ul><li>Over time, the stream can carve a steep canyon along its course. </li></ul>
  26. 28. Video
  27. 29. <ul><li>When water has a lot of energy, as it does when a stream has large volumes of fast-moving water, it carries and moves more sediment. </li></ul><ul><li>As water loses energy, it drops some of its load. </li></ul>Stream Deposition 1 Streams <ul><li>Heavier pieces of sediment drop out first , then the lighter pieces are deposited. </li></ul><ul><li>This occurs where the speed of the water decreases. </li></ul>
  28. 30. <ul><li>Water in a stream loses energy and might deposit sediment where the streambed becomes flatter, or where the stream channel widens. </li></ul>Deltas and Alluvial Fans 1 Streams <ul><li>As a stream empties into a body of water such </li></ul>as a lake, gulf, or bay, the remaining sediment is deposited, forming a delta.
  29. 31. <ul><li>The deposited sediment eventually raises the bottom of the water body, and the stream forms new channels through the deposit. </li></ul><ul><li>Eventually, the delta grows and new land is created. </li></ul>Deltas and Alluvial Fans 1 Streams
  30. 32. <ul><li>When a fast-moving mountain stream flows onto a flat plain or valley, a fan-shaped deposit of sediment, called an alluvial fan often forms. </li></ul><ul><li>Alluvial fans are similar to deltas, except that alluvial fans form on land , whereas a delta forms in the water. </li></ul>Deltas and Alluvial Fans 1 Streams
  31. 33. <ul><li>The volume of water flowing through a stream in a given amount of time is called stream discharge . </li></ul><ul><li>For example, if 200 m 3 of water flow past a point along the stream channel in 2 s, the discharge is 100 m 3 /s . ( Flow Rate ) </li></ul>Floods 1 Streams
  32. 34. <ul><li>Heavy rain or melting ice and snow can lead to an increase in discharge. </li></ul><ul><li>As discharge increases, the stream’s speed also increases and it can carry more sediment. </li></ul>Floods 1 Streams <ul><li>This can lead to erosion of the stream channel. </li></ul>
  33. 35. <ul><li>Sometimes a stream’s discharge increases so much that the river channel cannot hold the increased volume of water. </li></ul>Floodplains 1 Streams <ul><li>The floodplain of a stream is the region of </li></ul>land next to the stream channel that is covered by water during a flood.
  34. 36. <ul><li>When the water overflows its banks, it spreads out over the floodplain and the speed of the water flow decreases. </li></ul><ul><li>Sediment is deposited on the floodplain. </li></ul>Floodplains 1 Streams <ul><li>Floodplains help reduce stream discharge downstream, reduce erosion, and collect new, fertile soil from stream deposits. </li></ul>
  35. 37. <ul><li>One way to control a flood is to build artificial levees , which are mounds of soil placed on the sides of a stream channel. </li></ul><ul><li>Levees help keep the water within the channel, or from overflowing the banks. </li></ul>Controlling Floods 1 Streams
  36. 38. <ul><li>Flood-control dams store the additional stream discharge and/or let it out a little at a time, thus preventing the flood . </li></ul><ul><li>However, dams are expensive and can be difficult to build. </li></ul>Changing Stream Flow 1 Streams <ul><li>They also create large water areas that once were land, and they block the movement of river organisms. </li></ul>
  37. 39. <ul><li>Stream channels can be altered to hold more water. </li></ul><ul><li>Dredging the channel makes it deeper and straighter, allowing the water to move faster and perhaps preventing it from rising to flood stage. </li></ul>Changing Stream Flow 1 Streams <ul><li>This flood-control method is called channelization . </li></ul>
  38. 40. <ul><li>As more water moves faster, erosion of the stream banks and channel increases. </li></ul><ul><li>Often, trees that shade the stream and keep the water cool must be removed to channelize the river. </li></ul>Changing Stream Flow 1 Streams <ul><li>Cooler water has more oxygen and often has a wider variety of organisms in it than warm water does. </li></ul><ul><li>Increasing the stream discharge in one part of a stream can make downstream flooding worse. </li></ul>
  39. 41. <ul><li>The best solution to flood problems is to use the land wisely. </li></ul><ul><li>Identify areas of the floodplain that are likely to be flooded and then use the area appropriately. </li></ul>Changing Stream Flow 1 Streams <ul><li>Many communities carefully control development, permitting buildings only on areas above the floodplain. </li></ul>
  40. 42. Question 1 Section Check 1 Question 1 What three factors determine how much water runs off into stream channels? NC: 3.02
  41. 43. Question 2 1 Section Check Question 2 Which type of stream is shown here? NC: 3.02
  42. 44. Question 3 1 Section Check Question 3 Explain how new land can be created by streams. NC: 3.02
  43. 45. Answer 1 Section Check 1 Question 1 What three factors determine how much water runs off into stream channels? Answer The slope of the land, amount of vegetation on the land, and how much rain falls on the surface determines how much runoff there will be. NC: 3.02
  44. 46. Answer 2 1 Section Check A. braided stream B. meandering stream C. straight stream D. wide stream NC: 3.02
  45. 47. 1 Section Check Answer The answer is B. Streams that have channels with many curves are called meandering streams. NC: 3.02
  46. 48. Answer 3 1 Section Check Answer When a stream empties into a lake, sediment is deposited and a delta forms. The deposited sediment eventually raises the bottom of the water body and the stream forms new channels. The delta continues to grow and new land is created. NC: 3.02

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