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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 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 Outline the stages of the water cycle. Explain the components of a water budget. List two approaches to water conservation. Ahead to 13.2
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
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
Evapotranspiration Together the processes of evaporation and transpiration are called evapotranspiration
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
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
3. New Supplies of Fresh Water • Desalination Back to 13.1
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
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.
Watersheds of Virginia Back to 13.2
1. Stream Development • Headward Erosion: lengthening and branching of a stream
1. Stream Development Stream Piracy: the capture of a stream in one watershed by a stream in another watershed
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)
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
2. Channel Erosion—Discharge and Gradient higher gradient = higher velocity = more erosion lower gradient = lower velocity = less erosion
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?
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
3. Stages of a River System • Youthful River • V-shaped valley, steep sides • waterfalls and rapids common
3. Youthful Stage Yellowstone River
3. Stages of a River System Mature River • Floodplain developed • Few waterfalls and rapids • Has meanders and oxbow lakes • Lower gradient
3. Floodplain flood plain Mature Stage
3. Meanders and Oxbow Lakes Sevier River, TN Sweetwater River, Wyoming
3. Oxbow Lake • Definition: an abandoned meander loop
3. Stages of a River System Old Stage • Deposits more than erodes • Forms a broad, flat plain • Fewer tributaries than “Mature”
3. Stages of a River System Sevier River, TN
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
3. Stages of a River System • Rejuvenated Stage
3. Stages of a River System abandoned meander San Juan River, Utah • Rejuvenated Stage Back to 13.2
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
1. Two Types of Stream Deposition Mississippi River Nile River Delta—a fan-shaped deposit at the mouth of a stream
1. Two Types of Stream Deposition Death Valley, California Alluvialfan—a fan-shaped deposit at the base of a slope on land
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
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
3. Flood Control Devil’s Gate Dam, CA Artificial levee on the Mississippi River Direct control: • Dams • Artificial levees Back to 13.3
