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Chapter 13 Water and Erosion

Chapter 13 Water and Erosion. Chapter Outline. 13.1 The Water Cycle Water Budget Water Conservation 13.2 River Systems Stream Erosion Channel Erosion Stages of a River System 13.3 Stream Deposition Deltas and Alluvial Fans Flood Deposits Flood Control. 13.1 The Water Cycle.

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Chapter 13 Water and Erosion

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  1. Chapter 13 Water and Erosion

  2. Chapter Outline 13.1 The Water Cycle Water Budget Water Conservation 13.2 River Systems Stream Erosion Channel Erosion Stages of a River System 13.3 Stream Deposition Deltas and Alluvial Fans Flood Deposits Flood Control

  3. 13.1 The Water Cycle Outline the stages of the water cycle. Explain the components of a water budget. List two approaches to water conservation. Ahead to 13.2

  4. Stages of the Water Cycle • Evaporation – process by which liquid water changes into water vapor • Transpiration – process by which plants give off water vapor into the air • Condensation – process by which water vapor in the atmosphere expands and cools forming water droplets which then collect and form clouds • Precipition – process by which water falls from clouds to the earth’s surface • Runoff – water that flows over the land • Ground water – water that soaks deep into soil and rock

  5. 1. Stages of the Water Cycle Water Cycle: the continuous movement of water from the atmosphere to the earth’s surface and back to the atmosphere again • 6 ways water moves in the water cycle: • evaporation • transpiration • condensation • precipitation • runoff • groundwater 3 4 2 5 1 6 Back to 13.1

  6. The Water Cycle

  7. Evapotranspiration Together the processes of evaporation and transpiration are called evapotranspiration

  8. 2. Water Budget Definition: gains and losses of water in a region Factors that affect local water budget: • Temperature • Presence of vegetation • Wind • Amount and duration of rainfall Negative budget Positive budget Back to 13.1

  9. Earth’s Water Budget • Precipitation = Income • Evapotranspiration and runoff = expenses The earth as a whole is balanced because the amount of precipitation is equal to the amount of evapotranspiration and runoff • The local water budget usually is not balanced

  10. 3. Water Conservation

  11. 3. New Supplies of Fresh Water • Desalination Back to 13.1

  12. Life Without Water

  13. The Water Cycle

  14. 13.2 River Systems Describe the way in which a river develops. Explain how a stream causes erosion. Describe youthful, mature, and old river valleys. Ahead to 13.3

  15. River Systems • A river system consists of a main (trunk) stream and its tributaries • The land drained by these streams is called the drainage basin or watershed • Ridges or areas of high ground that separate watersheds are called divides.

  16. Watersheds of Virginia Back to 13.2

  17. 1. Stream Development • Headward Erosion: lengthening and branching of a stream

  18. 1. Stream Development Stream Piracy: the capture of a stream in one watershed by a stream in another watershed

  19. 2. Channel Erosion—Stream Load • Stream Load: the materials carried by a stream • Suspended load (fine sand and silt carried by the water) • Bed load (coarse sand and gravel that moves by sliding, rolling or saltation) • Dissolved load (dissolved mineral matter)

  20. 2. Channel Erosion—Discharge and Gradient • Discharge: volume of water moved by a stream within a given time at a given place • Gradient: steepness of the slope greater discharge=more erosion less discharge=less erosion

  21. 2. Channel Erosion—Discharge and Gradient higher gradient = higher velocity = more erosion lower gradient = lower velocity = less erosion

  22. 2. Channel Erosion--Quiz B A Which stream probably has greater discharge? B A Which stream has a higher gradient? A Which stream has greater velocity? A Which stream is probably eroding its channel more quickly?

  23. 2. Channel Erosion—Water and Wind Gaps Water Gap Water Gap Water Gap: deep notch left where a stream erodes through a mountain as it is uplifted Wind Gap: a water gap through which water no longer flows Back to 13.2

  24. 3. Stages of a River System

  25. 3. Stages of a River System • Youthful River • V-shaped valley, steep sides • waterfalls and rapids common

  26. 3. Youthful Stage Yellowstone River

  27. 3. Stages of a River System Mature River • Floodplain developed • Few waterfalls and rapids • Has meanders and oxbow lakes • Lower gradient

  28. 3. Floodplain flood plain Mature Stage

  29. 3. Meanders and Oxbow Lakes Sevier River, TN Sweetwater River, Wyoming

  30. 3. Oxbow Lake • Definition: an abandoned meander loop

  31. 3. Stages of a River System Old Stage • Deposits more than erodes • Forms a broad, flat plain • Fewer tributaries than “Mature”

  32. 3. Stages of a River System Sevier River, TN

  33. 3. Stages of a River System • Rejuvenated Stage • Cuts deeper into the valley floor • Slope of the land increased by movement of the earth’s crust • Often has characteristics of youthful and mature stages combined

  34. 3. Stages of a River System • Rejuvenated Stage

  35. 3. Stages of a River System abandoned meander San Juan River, Utah • Rejuvenated Stage Back to 13.2

  36. 13.3 Stream Deposition List two types of stream deposition and explain the differences between them. Describe the change in a stream that causes flooding. Identify direct and indirect methods of flood control

  37. 1. Two Types of Stream Deposition Mississippi River Nile River Delta—a fan-shaped deposit at the mouth of a stream

  38. 1. Two Types of Stream Deposition Death Valley, California Alluvialfan—a fan-shaped deposit at the base of a slope on land

  39. 1. Two Types of Stream Deposition Ganges River • Deltas: • Deposited in water • Made up of mostly mud • Surface is relatively flat Differences between deltas and alluvial fans: • Alluvial Fans: • Deposited on land • Made up of mostly sand and gravel • Surface is sloping Back to 13.3

  40. 2. Flood Deposits Floodplain—part of the valley floor that may be covered with water during a flood Natural Levees—raised riverbank that results when a river deposits its load at the river’s edges Back to 13.3

  41. 3. Flood Control Devil’s Gate Dam, CA Artificial levee on the Mississippi River Direct control: • Dams • Artificial levees Back to 13.3

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