Chapter 13 Water and Erosion

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.

17. Watersheds of Virginia Back to 13.2

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

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

20. 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)

21. 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

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

23. 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?

24. 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

25. 3. Stages of a River System

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

27. 3. Youthful Stage Yellowstone River

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

29. 3. Floodplain flood plain Mature Stage

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

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

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

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

34. 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

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

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

37. 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

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

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

40. 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

41. 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

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